Pontiac 6X head Information:

Taken from the Q&A page at  http://www.classicalpontiac.com

This information is for reference only, current as of 3/17/2000

Visit my site at:   Fred's Pontiac information

Email comments or suggestions concerning these help files to: fteufert1@worldnet.att.net

Topic: 6080

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- 6x heads use sm/lg valves - TONY SCOTT tony_a_scott@amat.com 1/27/99 14:59

I have a set of 6x heads at the shop and he asked me if I want to up size the exhaust valve. He said the labor charge is to install hardened seats on the exhaust side. $40 for the seats and $80 for the labor. My question is: Is it worth it (performance gain)to use the larger exhaust valves. It is a street car and I will use 10cc dome piston > 98cc head - 10cc = 88cc in a .030 over 400 should give me around 9.5 comp. Also I want to use a Lunati bump stick 235/235 @ .050 .507/.507 lift 108 loab centr ln. Do you think this cam is to big for a 3000lb stick car. Looking for power but streetability. Thanks

Responses

tboy Bio 1/27/99 16:49

You did not say what the rear end gears or the first gear in the trans. With 3000 lb and any reasonable gear combo you could get away with even more cam

jo jo Bio 1/27/99 17:03

too big?yes big ex valve?why not cam i would start out with is 215-220 at .050 L/s 112 on a 109 intk center .480 lift.i'm running same c.r. and have the 744 cam,and it kicks butt holes. stock cams are good to use.their is alot of post about stock cams.jim hand did a test with 068 cam 744,041.he used roads lifters for 041 and did a comparison test against the 744 but did not mention if roads were used with it too.the stock cams ran just as good if not better than performance cams.,he was also testing. i think this was the best low lift cam potiac ever made,stick to its specs but go with more lift when selecting a cam. As far as the valves go use the small valve ,run it ,then use the big valves and run it.get some timeslips and post\ them here and you will have solved one of the biggest debates this page has, in reguards to big v's small ex valves.

- tony 1/27/99 17:29

It has 373 gears . Why go with old tech. cams ? It 30 years later and i am positive cam builders are making better products. What do you think

- warrenk 1/27/99 18:37

Every camshaft made either "new" or "old" is junk unless it is matched to your application. The original pontiac grinds are very good grinds as long as you understand how to apply them. "We" like the Pontiac cams because they have a proven track record with different Pontiac engines. Most "new" pontiac cam are grafted ch**y or f**d grinds. The "old tech" Pontiac grinds were developed specifically for the pontiac engine by the engineers who knew the strengths and weaknesses of the Pontiac engine. That is not to say that the new cams are bad, but the key is to understand all the variables and match your needs and engines power/torque range with a cam. New isn't usually an indicator of a better product. For your combo I would look for cam with a duration around 224-230 degrees on the intake and 230-236 on the exhaust with an LSA of 110-108. The 1.66 valve will do fine, don't go too far over .500 lift.

obeid Bio 1/27/99 19:01

What about the timing from advertised (.004-.009) to .050? There is a substantial amount of degrees of overlap that occurs in the factory designs that is reduced in the newer designs. For example a 744 shows 301 and 224 but a newer ultradyne is 280 and 223. So the ramp is different by 20 degrees, and this is during the overlap period. Sure, heads don't flow as much below .050, but they do flow some, right? Anyone wish to comment?

Witchdoctor Bio 1/27/99 19:53

Obeid: How you doin? Much of that difference is between advertising hype, everybody had to have a 300 degree cam in 1969, and where the measurements are taken. I remember reading somewhere that Pontiac measured gross duration at .002" lifter rise, where the SAE specs that most cams today are rated by is at .006" lift. The factory ramps were a little soft for 50K. warranties, and this is where the "blueprinted" cams, such a Crane 041 clone got an edge. .050" duration and LSA are still the best guideline for street hydraulics, while the roller cam crowd pay a bunch of attention to duration at .200". I'm not totally convinced that the cam grinders are spending big R&D bucks on Pontiac cams. We sometimes benefit from stuff learned for SB Chevies, and from the work of concentrated Pontiac builders like Jim Butler, but most of the street grinds are still basically a pig-n-a-poke. WD.

- warrenk 1/27/99 20:57

If you had two cams with the same LSA & duration @.050 but one cam had a shorter overall duration. What benefits (if any) would one expect? Slightly increased dynamic compression? Improved idle characteristics? Would the "faster" events cause the valve train to wear-out prematurely?

Witchdoctor Bio 1/27/99 21:15

warrenk: It still depends upon where the grinder measured gross duration. If you play with a degree wheel and a dial gage, those first few thousandths eat up lots of degrees. But, yes, a more aggressive lift rate is harder on the cam, lifter and spring. It is like the difference between tapping lightly with a hammer, and smacking the heck out of what you are hitting. Dynamic compression is a factor of when the valve seats, but you pose an interesting question that could only be resolved by flow testing under .050". One could think that the reduced window of a 45 degree intake seat would increase dynamic compression as opposed to a 30 degree seat with the exact same cam. Good stuff to think about until the races get back on TV. Hey, congratulations to Eddie Cheever, and the Pontiac man on the BB who builds his engines. WD.

- Eric D. egdmilw@milsolv.com 1/27/99 22:00

The question is, how fast do you want to go and is the larger valve needed? A '68 GTO that runs in our group has a combination similar to mine. He has 6X's with the 1.66" valve and runs 11.80 @ 113 MPH. In this case, the motor has lots of cam to make up for the smaller valve. I have read some data that indicates the 6X flows as much as other D-ports that have the 1.77" valve. Personally, I did not think it was worth the time or expense on my engine and I used stock valves. I dedided to spend money where I thought it would be more beneficial. There is many other areas you can make up for the smaller valve. It's like the guys that buy stainless, swirl polished valves and runs a 2 1/4" exhaust system with stock manifolds. A lot of good those valves are doing with small exhaust! Sincerely, Eric D.

Stevie Ray Bio 1/28/99 3:23

From your post it sounds like your replacing the valves and the seats anyway so going to the larger valve would be a good idea. I had a cam about that size in a GTO 20 plus years ago and I thought it was streetable if you dont mind a rough idle(shook the windows in my Dads house!!) and eye burning exhaust...but it did have S-loads of power./3000lb car? what is it?

- Lee ..\members/html/455.html..\members/html/455.html1/28/99 12:45

What is wrong with the seats in heads already? Many years ago I had 1.77"s installed in a set of 6X's. The shop just opened the throat to match the bigger valves. I put 25,000 miles on the heads, and the next owner put alot more than that, and we never had any problems.

- tony 1/28/99 13:25

He said if he has to open up the seat area he will go to deep into the hardend seat and expose softer metal. Since these are unleaded head originaly he will have to insall new hardend seats for the exhaust valves. tony

- Lee ..\members/html/455.html..\members/html/455.html1/28/99 13:36

Your money, but I had the same heads, and ran a long time on unleaded gas with no problems.

Witchdoctor Bio 1/28/99 20:40

I agree with Lee. A lot of this seat regression with unleaded fuel has been just smoke. Unless you are running flat out for minutes on end, there is very little difference between the old de-carbonizing and valve lapping at 30K. that was accepted in the old days with leaded fuel. WD.

- 2/1/99 15:31

Sound like he is trying to sell you unnecessary machine work. Pontiac does not have "hardened seats". The heads are high nickel content iron, no need for seats. The 1.77 valve installation, when done properly, actually flows better than the factory 1.77. The factory throat cut, which is straight, leaves no radius, which hurts low lift airflow. This is why all Pontiac cams had 15-20 degrees more dur. on the exhaust side, trying to fix a problem with a problem. When one opens up the factory 1.66 seat, one can get a decent radius, three angles, which vastly improves airflow off the seat.

- TONY 2/1/99 18:10

So there is no differenc between lead gas heads and unleaded gas heads ? Tony

padgett Bio 2/1/99 18:27

The part number/casting number sizes headdocument I quote values from occasionally is dated 4-29-85 and separates "EXH SEAT" into "soft" and "hard". First "hard" is the 1971 486071 (casting 486075 also used for most '72s). Late 16 (455 SD) is only one listed to have "inserts". Generally, the easy way to spot a Pontiac cam for stock D-port heads will have about 10 degrees more exhaust duration. Even specs are an indication that it may be a derivation from something else.

Topic: 6361

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- 6xheads - rwatson rwatson@bright.net 2/9/99 20:20

I picked up a set of 6x heads cleaned and magnafluxed for $40 to use on a 455. Later, I discovered one is a 6x-4 and the other is a 6x-8. Is there any way to use these two on the same engine? (now I know where to look for 4's and 8's!!). thanks rwatson

Responses

ta_dragracer Bio 2/9/99 21:03

The combustion chambers are different sizes. If you attempted to mill the 8 to come to the size of the 4, I think you might have manifold problems. Would probably be best to replace one or the other.

Witchdoctor Bio 2/9/99 22:36

I've been cussed and discussed because I don't think the 6X/4 head is the greatest thing since peanut butter. Take your head gasket and scribe the chamber opening on both heads. All of that iron hanging out into the chamber of a 4.181", .030" 455 bore ain't going to get you a thing. You can grind on the sucker for many hours, and hand make a 6X/8, but you would be better off to go find another one. This all got started on the CC 406 eingine article, but the 455 is a different ball game. WD.

67 GOAT Bio 2/10/99 8:58

The very same thing happened to me. Excpet a guy gave them to me. Before I accepted, I looked at one and it was a "4". I was in a hurry so I didn't bother to look at the other. Two months later I was thinking on building the heads and trying a home port job for the first time. Got them both out and the one I looked at was a "6". I sware the looked identical as of the were of the same motor. Probably were. Any way, rwatson, if you need a single 8 or 4 let me know and I will give one or both to you if you pay shipping.

- tony 2/10/99 10:09

I still can not find a 4 or 8 on my 6x heads ! Where exactly is it ?

- Martin Lansky mlansky@vossnet.de 2/10/99 16:19

Tony, put the head on a table, intake side down. Now, you´re looking at the exhaust side. There is a boss running from spark plug hole to just below the valve cover rail. The boss has a machined down area just below the valve cover rail. That´s where the number 4 or 8 is stamped. Hope this helps, Greetings from Europe, TAMartin.

jo jo Bio 2/10/99 17:51

$40.00 for one head an't bad .especialy if it's a 6x #4.but you better off with the #8 and besides it will be easier to find one to match

- rwatson rwatson@bright.net 2/11/99 15:54

Thanks for the info and help-this is a great website for pontiac people.

- Ron Wagner rcwagner@bellsouth.net 2/12/99 22:51

I was planning to put a set of 6x-4s on my 455. How much of a loss will there be compared to a set of 6x-8s. I compared them to a set of 4x's off a 400 and I see what you mean by the chamber not being cut for the larger bore. Has anyone run them on a 455 and been dissapointed or had a problem? Has any one done a side by side test of the 6x-4s vs the 6x-8s on a 455? I would love to know more before I put them on or abandon them. Thanks for any help. Ron

Topic: 6422

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- 6x on 455 - barryh Bio 2/12/99 20:15

i have my choice of the #4 or#8 heads, ill use the new k-b pistons at .030.they should be at about 0 deck hight when installed. should i save the money on milling my heads(8's).030, or use the 4's and leave them as is. the car will be a weekend warrior.someone was saying the ridges on the 350 heads would protrude more into the bore.so the 400 heads would be better if i was going to add 1.77 exaust valves?(shrouding)any advice would be appreciated. thanks barry.

Responses

Witchdoctor Bio 2/13/99 17:34

Barry: I'm the guy who does not like the idea of the 350 chamber on the large bore, and I am working backwards from what we have found to work the best on two 11.80, full weight bracket racers. If you go back and look at the really fast Pontiac factory engines of the past, they featured valve reliefs in the top of the cylinder bores to aid airflow. The old NHRA racers could not do anything to the heads, so their only avenue to increased power was high compression, and mega lift roller cams. The bore valve reliefs hurt compression, so they either decked the block to remove them, or used later smog blocks, which the bean counters eliminated the extra machining operation. Nearly every one understands that air/fuel mixture flow into the ports does not like sharp protruding edges, but many working with just heads on flow benches ignore other factors going on within the working engine. Any sharp edge hanging out into the combustion chamber is going to create a hot spot, which raises the mechanical octane requirement of the engine. Secondly, visualize the flow WITHIN the cylinder as the piston is rapidly charging up on the compression stroke. By having the small chamber surfaces hanging out in the direction of flow, you are creating additional squish areas that move the mixture AWAY from the plug and the spark origin. This train of thought is exactly why Pontiac went to the open chamber head. What has worked best for us, and we are poor boys that do our testing at the track, is that the engines respond best if the combustion chamber cavity is seen by the piston deck as a seamless extention of the bore. We are running less static compression, less ignition advance, and going faster. It's just food for thought. WD.

Topic: 6441

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- 6X heads #4,#8 ? - Mark lemans70@wf.net 2/14/99 3:09

I was reading post #6361 and learned there are certain numbers located on a runner extending from the top of the head to one of the spark plug areas. I checked mine and it has the #4. Can someone explain what this number means and what other numbers can be found on these heads. I had my heads cc'd and was told they are 92 cc. Thanks :-)

Responses

67 GOAT Bio 2/14/99 7:31

Place the heads valves down look at the exhaust side of the head. There will be "tabs", pads, or bosses towards the top of the head. Usually the front two tabs on the passenger side head are used for A/C mounting. There should be another tab towards the rear of the head. On the pad part there is a number stamped, not cast. You should see a "4" or an "8". It has been discussed several times to great extent on this board and I think the outcome was that the "4" meant use on a 350/400 block, usually a smaller combustion chamber than the "8" which was used on 400/455s. I think the usage area is still somewhat fuzzy, as is the combustion chamber size. It is best to have them cc'd. Personally, I cc'd a set of "4" and got approximately 96.3cc. "8" had approximately 103cc. But others have had different results than I. Hope this has helped somewhat.

- al 2/14/99 8:36

I have yet to see 6x heads on a 455 from the factory. I have seen plenty of 6H however.

67 GOAT Bio 2/15/99 9:58

al is right. I don't think the 6Xs were on the 455 from the factory. Sorry. However, they sure work good on a 455.

Calvin Craig Bio 2/15/99 14:07

Yes, they were on a 455, I pulled a 455 from a '76 Grand Prix in a junkyard that had 6X's. They had HUGE chambers.

67 GOAT Bio 2/15/99 21:20

We stand corrected. I think the 6Xs are fuzzy in both what they came on and chamber sizes.

Topic: 7012

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- 6x head porting - ronbob Bio 3/10/99 0:43

I am slowly getting a set of 6x heads ready to install on my 455 in place of the 4xs that are on it now. I am going to do a porting job myself. My question is how much material can be removed at the throat of the intake runner on the side with the push rod boss without getting to thin or going through. I am not a math major so please state measurements in inch increments. (1/32, 1/16 etc) Thank you for the help.

Responses

- Jack Ferris jferris4@burgoyne.com 3/10/99 12:33

Ron E mail me when you get a chance and I'll give you some specs.

pontiacron Bio 3/10/99 18:42

ronrob,from figures from our flow bench the push rod bulge doesnt affect flow as much as you think,it just looks restrictive.The on coming air wants to huge the other wall.Grind the bulge a little.Concentrate on the valve bowl and smooth radius instead.

- Brian Baker bkbaker@att.com 3/10/99 18:51

I agree with P-Ron, don't be too overly concerned with removing alot of material from the pushrod bulge...You biggest gains will be from blending the bowls ("pocket porting") and then you can move on to the ports...You can widen the wall opposite the bulge to increase flow somewhat...Also remove the EGR "bumps" on the roof of the exhaust ports...Although it won't gain you much flow, polishing the exhaust ports will help cut down on carbon buildup

Witchdoctor Bio 3/10/99 19:46

Clean the pushrod hole and use a length of 1/2" od. tubing as a guide. The side of the hole for practical purposes is aligned laterally with the vertical wall of the port. I take off .090" (3/32") and ease the created flat into a gentle radius in and out. For a race head, I sleeve the pushrod holes ala the SD-455. This is one of those areas where I disagree with flow bench numbers. Air is still a fluid, and the most efficient passage is a straight line of sight. I also think that thining the divider wall inside the port does nothing. Flow benches say one thing, but the time slip tells all. WD.

jo jo Bio 3/11/99 4:01

I' have to agree with w.d. That buldge is like a tree in the road.Knock it down until your just barely going through with a biggest radius you can get. But to utilize that flow potential it must welcomed to the rest of port so also widen floor at throat,Do NOT LOWER IT.Ive gotten 240 cfm @28in with only a 171 cc port at 550 lift, and these are also 6x heads.Also raise the roof about .080.well gotta go to work.jo jo

Witchdoctor Bio 3/11/99 21:19

Jo Jo's got it right. On a Pontiac head, you want to maintain the venturi shape just below the seat. Do not lower the short turn floor, it is already too low. The only thing left is to widen the sides of the turn. Check Dave Vizard's SB Chevy porting information. It explains why a bulge at the turn of a conduit reduces flow loss created by the turn. WD.

Topic: 7012

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- 6x head porting - ronbob Bio 3/10/99 0:43

I am slowly getting a set of 6x heads ready to install on my 455 in place of the 4xs that are on it now. I am going to do a porting job myself. My question is how much material can be removed at the throat of the intake runner on the side with the push rod boss without getting to thin or going through. I am not a math major so please state measurements in inch increments. (1/32, 1/16 etc) Thank you for the help.

Responses

- Jack Ferris jferris4@burgoyne.com 3/10/99 12:33

Ron E mail me when you get a chance and I'll give you some specs.

pontiacron Bio 3/10/99 18:42

ronrob,from figures from our flow bench the push rod bulge doesnt affect flow as much as you think,it just looks restrictive.The on coming air wants to huge the other wall.Grind the bulge a little.Concentrate on the valve bowl and smooth radius instead.

- Brian Baker bkbaker@att.com 3/10/99 18:51

I agree with P-Ron, don't be too overly concerned with removing alot of material from the pushrod bulge...You biggest gains will be from blending the bowls ("pocket porting") and then you can move on to the ports...You can widen the wall opposite the bulge to increase flow somewhat...Also remove the EGR "bumps" on the roof of the exhaust ports...Although it won't gain you much flow, polishing the exhaust ports will help cut down on carbon buildup

Witchdoctor Bio 3/10/99 19:46

Clean the pushrod hole and use a length of 1/2" od. tubing as a guide. The side of the hole for practical purposes is aligned laterally with the vertical wall of the port. I take off .090" (3/32") and ease the created flat into a gentle radius in and out. For a race head, I sleeve the pushrod holes ala the SD-455. This is one of those areas where I disagree with flow bench numbers. Air is still a fluid, and the most efficient passage is a straight line of sight. I also think that thining the divider wall inside the port does nothing. Flow benches say one thing, but the time slip tells all. WD.

jo jo Bio 3/11/99 4:01

I' have to agree with w.d. That buldge is like a tree in the road.Knock it down until your just barely going through with a biggest radius you can get. But to utilize that flow potential it must welcomed to the rest of port so also widen floor at throat,Do NOT LOWER IT.Ive gotten 240 cfm @28in with only a 171 cc port at 550 lift, and these are also 6x heads.Also raise the roof about .080.well gotta go to work.jo jo

Witchdoctor Bio 3/11/99 21:19

Jo Jo's got it right. On a Pontiac head, you want to maintain the venturi shape just below the seat. Do not lower the short turn floor, it is already too low. The only thing left is to widen the sides of the turn. Check Dave Vizard's SB Chevy porting information. It explains why a bulge at the turn of a conduit reduces flow loss created by the turn. WD.

Topic: 7117

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- max cc off 455 6x heads - tim 3/14/99 18:23

I would like about 10:1 in a 455. My heads are 101 cc and the block has been decked .010. The bore is .060 pistons are stock forged. I am running a solid lifter cam at .550-.580 lift with 1.65 rockers. How much can i take off of my heads befor my valves hits?

Responses

77ta Bio 3/14/99 20:35

Id e-mail JIm HAnd with that question sounds close to what he's running.

- tim 3/14/99 21:19

what is his e-mail

Steve Chin Bio 3/15/99 18:40

Tim, the most you can take off of a set of Pontiac heads without running into structural problems is 0.060" You aren't going to get to 10:1 with those heads. Start shopping for a set of 8.4:1 400 heads or a set of #64 heads.

- Brian E. bevans@flex.net 3/24/99 22:02

Tim, I agree with Steve, 101cc heads are not going to give you what you want. Edelbrock 87 cc heads would fill the ticket, though they will empty your pocket! I am building a 455 using 1975 5C heads off a 350. I measured these heads at 93cc, which is probably how PMD kept compression parity between the 350 and 400 engines. The 5C has 2.11 intake and 1.66 exhause valves. The small exhaust will not hurt you below about 5000 rpm, though your can hog it out to 1.77 if you want. Valve seats are hardened, too. Use the compression calculator at chevelles.com (under restoration) to help you with dialing in the combustion chamber volume you need. Good luck! Brian E.

- Todd farland@cts.com ..\members/html/4.html

..\members/html/4.html3/24/99 22:54

Ummmm, there's a compression calculator right here at this site (along with head specs, bore sizes, etc). Click on the "Restoration" button at the bottom of the page....

Topic: 7186

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- 6X 455 spark plugs? - jjump Bio 3/17/99 18:59

Ok, got the engine built, now need to know what plugs I should start out with. I've got 1975 350 6X heads on my 70 455, .030 over, HEI, 70 cast intake, summit 2802 cam with rhoads type lifters (crane), H/S roller rockers. The crossover in the heads are filled with aluminum. any suggestions?

Responses

- Brian Baker bkbaker@att.com 3/17/99 19:40

If you plan on using AC's, try R-44's to begin with. You can always go to a hotter range after you see how these perform. Then you can step-up to a '45 and see how that works. If you experience any detonation (especially under light throttle loads) then you'll have to step back in the heat range (to a '44).

- 3/17/99 20:08

coldest possible

- Lee ..\members/html/455.html

..\members/html/455.html3/17/99 20:21

Autolite 666's. Hard to forget that number.

- Brian Baker 3/17/99 20:30

Lee, I respect you opinion. How do the autolite's compare to the AC's. What type AC's were you running before you discovered the autolites?

Steve Chin Bio 3/17/99 20:45

I liked the Bosch Platinums with the MSD, but without MSD, the AC plugs were great too.

Johnathan Bio 3/18/99 9:41

Bosch Platinums all the way!! but I did run rapid fires in my 78 formula and for a while in the '67 and they improved idle, but not any gains over the bosch platinums. but where an inprovment over the delco coppers

- Lee ..\members/html/455.html

..\members/html/455.html3/18/99 16:54

Brian, it has been several years, but I tried the ACs that were standard for 220hp 400's, R45TSX I believe. I never tested plugs back to back on the same day, but I did do several plug swaps and ran several times at the track after each swap. The best times I ever got were with the 666's. I swapped back to AC's after using the 666's for some time, and noticed my e.t. was down a little. Left them in for a few months, swapped back to a fresh set of 666's, and the e.t. came back. It wasn't a huge change, less than a tenth, but I ran the car enough to notice it. I've got another local guy running 666's in his 455/6X, and they are doing fine.

jjump Bio 3/18/99 17:07

thanks for the response, i've used autolight plugs in my race cars and will probly go that way. just was not sure what numbers to start with. i'll keep the AC R44 in mind. thanks again.

Topic: 7200

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- told no diff between 6x - gregg 3/17/99 23:20

called rock and roll and asked about 6x-4 heads and was told that 92/98 cc thing was made up and not true. can you beleive it?

Responses

- Ron Wagner rcwagner@bellsouth.net 3/18/99 1:03

I have only cc'ed a few 6x heads but all the 4's were 98cc. RW

geebjen Bio 3/18/99 8:41

I've read post after post over the past year about 6X heads. The only conclusion I've come to is that the 6X-4 have smaller chambers, in general, than the 6X-8. I just got a set of 6X-4 that as supposed to be uncut and I can't wait to cc them.

Johnathan Bio 3/18/99 9:39

my old 78 forumla had 6x-4s on its 400, but I never pulled them off to cc them.

- John 3/18/99 11:17

Sorry guys but if Jim Hand says it is so, it is so. I don't care WHAT RRE has to say about it.

- John V. 3/18/99 11:57

Lots of stuff in the archives, under post 5137, Bruce Fulper (R&R right?) states he was coming up with the same info as everyone else. Doesn't make any sense that he has changed his opinion. Gregg, are you sure you understood what you were being told. Same post, yours truly theorized there might have been 2 different cc's for each of the 6X-4 and 6X-8 since Pontiac boosted the c.r. of the reg. 400 & W72 motors between '77 & '78. I suggested it as a possible explanation for the c.r. change and the variety of cc's measured on the 6X-4 & 6X-8 heads. Perhaps R&R was disputing my theory to which I take no offense, it's just a theory looking for proof! I really doubt they are disputing the physical difference between the 6X-4 and 6X-8 versions.

- Stephen sugardog@flash.net 3/18/99 12:21

PLEASE, OH PLEASE don't start up the Hand v. Fulper stuff again. We don't need anymore of that b.s. Please, stick with informative and CONSTRUCTIVE Pontiac dialogue.

- Joel Koontz@bedford.net jwkoontz@bedford.net 3/18/99 19:38

I bought a set of 6x #4 heads off of a 77 350 that appeared to be untouched. They were 91 ccs. I had a valve job done and 1.77" exhaust valves installed and the heads were milled .015". I also opened/cleaned up the chambers. I used new valves with depressions in the center(stock were flat). After being worked on they were 98 ccs. A valve job can add several ccs to chamber sizes. As the seats and valves are ground it sinks the valves into the heads and increases chamber sizes. I'll bet a lot of the 6x #4 heads that cc over 92 have had one or more valve jobs. Good luck, Joel

Jim Hand Bio 3/18/99 19:41

I have worked with several other folks trying to unravel the 6X head subject, but without complete success. Here are some things we are sure of: Pete McCarthy did exhaustive research into Engineering records prior to publishing his latest Book, and he listed the chamber volume of one type head as 91.9, and the other as 101. As NHRA allows similar values in the race classes, it would appear that they obtained similar numbers. I have obtained the MVMA Specifications for Passenger Cars from Pontiac for all engines 1976-1979. This official documentation lists the two 6X heads as 93.74, and the other as 100.4. These are not Engineering design documents, but documents required from each car maker by the Government. I have measured two high CR 6X heads (marked -4) as exactly 92 cc, and on the same equipment and during the same session, measured several -8 6X heads as 101. However, other very capable folks have measured the- 4 as ranging from 92 to 98. It does appear that most measure the -8 as 100-101cc. We also know positively that some -4 heads on the late HP 400 were 96 cc. So, it is not possible to classify the -4 heads as a specific volume. As posted earlier in this thread, the -4 models do seem to be lower volume then the -8 heads. However, the only way to determine the volume is to obtain accurate cc measurements. It should be noted that a typical valve job using the same valves and seats will add 2-3 cc to the chamber volume, due to the valves dropping further down into the chamber. I no longer doubt any measured numbers, but would request from anyone that has access to both a -4 and -8 head to measure both using the same equipment and setup. This would minimize any chance of equipment variance between each of us. I am not compiling or publishing anything on this subject, but continue to be interested and wonder how Pontiac used the heads, manufactured such a variety of chamber volumes, and why the Engineering documents Pete used for his reference do/did not show the variety we are finding. Thanks for the comments and input on this subject. Jim Hand

Jim Hand Bio 3/18/99 20:27

Additional Information on the 6X heads. I mentioned that I had measured two -4 heads and several -8. I meant and should have stated that we measured two sets of -4 and several sets of -8 heads. The initials MVMA were mentioned, and they represent Motor Vehicle Manufacturers Association. The Specification form used for reporting such information is MVMA-40A- (year), and was developed and is used by automobile manufacturing companies under the auspices of the Motor Vehicle Manufacturers Association, and not the US Government. Jim Hand

- Bruce Fulper pontiac@primenet.com 3/18/99 21:36

I haven't changed our views. This thread/post is simply another attempt to start a controversy. As always, look at the names. No emails and only the cowards do this. Boneheads.

- gregg ginman@iquest.net 3/18/99 22:58

gregg/ginman@iquest.net

- gregg ginman@iquest.net 3/18/99 23:38

bruce, i wasnt involved in the post about your roller cam at all. if joe blow would of said there is no diff between the 6X's i wouldnt have gave it a second thought but when someone that does this for a living says something different then common opinion it makes me want to get to the truth

- Bruce Fulper pontiac@primenet.com 3/19/99 0:11

The first post on this thread is not an innocent question concerning cylinder heads. Who ever this was, be it you or whoever, it was out of line.

geebjen Bio 3/19/99 7:30

First, I agree with Stephen (sugardog) No arguments, just constructive info. Second, I cc'd one chamber of a pair of 6X-4 heads last night which were cast on J166 and it was 93-94 cc's. I have no idea of the history of these heads but was told they were unmodified originals.

geebjen Bio 3/19/99 9:05

I just wanted to add, on a positive note, that just 1 year ago I had never even looked at a REAL Pontiac engine. Just 1 month ago I had never seen a 455. And just 2 weeks ago I had never looked at a combustion chamber. And still I felt completely comfortable pulling the heads from my 455, identifying the 6X heads I just bought and cc'ing the heads, thanks to the wealth of knowlege I've gained in the past year by following this Q&A. Let's continue with information exhange and knowlege sharing.......

- sensei 3/19/99 9:28

You've learned well, grasshoppa

- John 3/19/99 10:58

Bruce- My earlier post on this string states that if Jim Hand says it is so, it is so and that I did not care what RRE had to say. Sorry for being so harsh on you as you too have helped me in the past. The message that I meant to convey was that if Jim Hand says it is so, it is- I trust his opinions and research regardless of what ANYONE says. I am sorry that I seemed to single you out but it was just that RRE was part of the original poster's question. I should have not jumped to any conclusions based on a posting unless I heard it with my own two ears. Please consider this as a public apology to you and RRE. No hard feelings? John

schwartz Bio 3/19/99 12:01

Can't we all just get along?

- John V. 3/19/99 12:18

I stand by my question to Gregg, is it possible you didn't understand what RRE was telling you? This seemed to me only logical explanation, since I knew Bruce F. was on the same page as everybody else about different 6X heads. I certainly didn't ask the question to offend Gregg and surely Bruce F. doesn't need my help to defend himself. Now I invite all to go over to topic 7213 to discuss more about the 6X w/ Geebjen. Seeya there.

- Bruce Fulper Pontiac@primenet.com 3/19/99 21:15

I, of all people, am extremely careful when talking about Pontiac produced engine parts. As witnessed w/ McCarthy's book, which I helped gather a lot of head and block data for. It's in it's seventh revision at least. As details concerning previous assumptions have been found out to be different, updates have been made. As stated by all of us that have done extensive (ongoing) research on part numbers, etc., Very little is etched in stone with this stuff. So regardless whom you put your faith into, remember that a lot of what is witnessed amounts to a small slice of the overall total production. I bet I've built as many Pontiac engines as anyone except maybe Nunzi, (400 plus) and, does that make me an expert on, say 455 block cylinder thickness? Nope. When the question is asked, what's a practical answer? *No* *one* *knows.* You must measure each one to find out. No year is better than another. But boy the assumptions that go around are amazing. (To me anyway.) Because the fact is, most guys have only been subject to a minor handfull of blocks, heads, etc. Millions were produced. It looks like we're are zeroing in on these -4, -8 number thing, but we haven't found enough repetition at my place to make any blanket statements yet. Let's keep looking........ Oh yeah, apology accepted.

Topic: 7213

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- 6X 350 vs 400 - geebjen Bio 3/18/99 13:08

As I understand it 6X heads were installed on both 350's and 400's. There is obviously some debate as to whether 6X-4's were ever installed on 400's and 6X-8's on 350's. Let's forget that for now. My question is this. Is there a difference in the size of the chamber AT THE SURFACE? I'm not talking cc's here, but the size of the opening if you layed a ruler flat across the chamber and measured it.

Responses

- John V. 3/19/99 13:04

From Pont. Enthusiast, there is a difference in the machining around the plug hole, smaller cut for the 350 head. Jim Hand had some good info in topic 7200 on cc's. Here's a thought, since the 350 was gone in '78, is it possible the 6X-4 used in the last W72's was not or at least not always the 350 6X-4? Is it possible that the 96 cc heads Jim Hand refers to were machined to the 400 6X-8 config. then milled and stamped with a 4? The "real" 350 6X-4 heads had a smaller chamber dia. (for lack of a better way to distinguish it from a 400 head). Do all the W72 heads have the smaller cut?

Topic: 7223

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- 74 bonnie with 6X - gregg 3/18/99 23:12

went looking at junkyards and found a 74 bonnie with 6X(8) heads and chrome covers on them. It really looked untouched, as in original. could it be?

Responses

- Todd farland@cts.com ..\members/html/4.html

..\members/html/4.html3/18/99 23:39

The valve covers aren't, but that doesn't mean that someone didn't add them when the car was new.

- John V. 3/19/99 9:27

Heads aren't, 6X heads didn't come out until late '75. Check for date codes.

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Topic: 7339

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- 6x's to #13's - Kraig Ruebush KA-Ruebush 3/24/99 9:58

Thanks for the help on switching heads but does anyone now where to get #13 heads and what they would cost and does anyone think it is worth switching from 6x heads on my 400 or is there a better way to get some more horses (already changed cam to RA III).

Responses

Johnathan Bio 3/24/99 10:48

they are around, just keep an eye out for them

Johnathan Bio 3/24/99 10:49

they are around, just keep an eye out for them

Steve Chin Bio 3/24/99 17:14

Kraig, when you go junkyard hunting, look for 400 poerted '70 Firebirds, LeMans', Grand Prixs, and big cars. The #13 head was commonly found on those models with 400 engines and automatic transmissions. Also, check out some of the swap meets and such. You might even find a set in the classifieds here.

- Kraig R 3/25/99 10:20

thanks steve that was the answer I was looking for

kitch4 Bio 3/25/99 14:41

I have a set but the 428 won't let them go. It screams "I LIKE IT" out the tail pipes. Seriously though, get ready for some high CR if you find some. Spark knock could become a problem if you decide to make this switch.

Witchdoctor Bio 3/25/99 20:21

Keep looking. If you can stand the compression, the #13 is one of the better small-chamber D-port heads. They have a very small intake guide boss, and no added exhaust port impediments. The "Heavy" car, a fully street-dressed `72 T/A, with frame connectors and a cage, with a 200 lb. driver got out for the first time last weekend, and knocked off a bunch of low 11.80s to get into the finals with #13 heads. Hate to say it, but red-lighted in the finals. WD.

pontiacron Bio 3/25/99 22:22

KA-Ruebush, I can help you with your head search. E-mail me at pontron@enteract.com

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Topic: 7444

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- 6x and 66 Head Comparison - ES touchstone71@yahoo.com 3/28/99 0:19

I am well aware of the versitility and availability of the 6x number 4 heads. They are great for low end flow and torque. I also know that the 71 #66 heads have an extremely good flow quality. I have recently been told by a reputable pontiac source that they range just below the ram air III heads and 71HO heads in air flow characteristics. Since I have a pair of each and am starting a 455 rebuild for street and occasional strip use, I want to know which heads will be more suitable. As I understand it, the 6xs will give me the proper compression (9-9.3:1) but will be limited on upper rpm performance with out significant head work. The 66s have great flow capabilites but have a large volume and will limit my compression. I want solid performance up to 4800 rpm with a 3:23 rearend and mild gasket matching. Which should I go with?

Responses

jo jo Bio 3/28/99 9:01

If i were you i would get flow sheets on both heads then compare them.

77ta Bio 3/28/99 13:37

if your only worried about up to 4800 go with which ever you can get and set up the cheapest. I have been told that there is not enough flow difference in any of the D port heads to worry about it just get the chamber volume you want.

- Eric D. egdmilw@milsolv.com 3/29/99 7:33

Too many people get excited about flow numbers. Pete M. has written many articles and indicated, most D-ports flow about the same. I have seen many stock 6X head cars with solid cams, running mid 11's or better. I use 6X heads with stock valves in my street car. I shift at 5,500 RPM and the motor has pulled over 6,000 (on accident). Peak power is around 5,200 and I run 108 MPH through the exhuast on street tires. I would use the heads that provide the best compression, around 9-9.5:1. Eric D.

Topic: 7444

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- 6x and 66 Head Comparison - ES touchstone71@yahoo.com 3/28/99 0:19

I am well aware of the versitility and availability of the 6x number 4 heads. They are great for low end flow and torque. I also know that the 71 #66 heads have an extremely good flow quality. I have recently been told by a reputable pontiac source that they range just below the ram air III heads and 71HO heads in air flow characteristics. Since I have a pair of each and am starting a 455 rebuild for street and occasional strip use, I want to know which heads will be more suitable. As I understand it, the 6xs will give me the proper compression (9-9.3:1) but will be limited on upper rpm performance with out significant head work. The 66s have great flow capabilites but have a large volume and will limit my compression. I want solid performance up to 4800 rpm with a 3:23 rearend and mild gasket matching. Which should I go with?

Responses

jo jo Bio 3/28/99 9:01

If i were you i would get flow sheets on both heads then compare them.

77ta Bio 3/28/99 13:37

if your only worried about up to 4800 go with which ever you can get and set up the cheapest. I have been told that there is not enough flow difference in any of the D port heads to worry about it just get the chamber volume you want.

- Eric D. egdmilw@milsolv.com 3/29/99 7:33

Too many people get excited about flow numbers. Pete M. has written many articles and indicated, most D-ports flow about the same. I have seen many stock 6X head cars with solid cams, running mid 11's or better. I use 6X heads with stock valves in my street car. I shift at 5,500 RPM and the motor has pulled over 6,000 (on accident). Peak power is around 5,200 and I run 108 MPH through the exhuast on street tires. I would use the heads that provide the best compression, around 9-9.5:1. Eric D.

Topic: 7472

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- 6X on 65 389 - Joe 3/29/99 8:20

Will I encounter any problems if I install 6X-heads on a 65 389.

Responses

- Ron H ron@unidyn.com 3/29/99 13:42

For performance purposes I would only use the small chamber 6X's (92cc's roughly) and even then you'll only have around 8.0:1 CR with a .030 overbore and assuming a .020 deck height. You can zero deck the block and shave the heads .050 to get up closer to 9.0:1. The large chamber 6X's would provide very poor CR on a 389, do you know which version of 6X you have?

- Joe 3/29/99 15:24

The ones that I plan to use were pulled from a 350 .So no other problems other than CR?

- Brian Baker bkbaker@att.com 3/29/99 20:36

Also of concern is the difference in layout of the valves between 389 heads and the later 6X's...The 6X valves were at a differnet angle than the 389's and in addition were "spread out" in the chamber a minute amount. I'd be concerned about piston to valve interference, most of all (particularly if you're running a larger cam). Scrutinize all clearances.

- Ron H ron@unidyn.com 3/30/99 13:21

Good point Brian, forgot about that one! Also, if you are using the stock intake manifold it may not match up with the warm air crossover ports on the 6X heads, someone else may know more about this.

- Joe 3/30/99 18:10

I'm going with the intake from the same 350. My concern was valve clearance.As for cam I'll be using stock cam for 65 GTO-389 4spd.

Topic: 7850

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- RA 3 manifold on 6X - gregg 4/14/99 17:16

will a RA 3 repo fit a 6X head? I think the guy at RA Rage in Dallas was telling me it wouldnt but I could of misunderstoud him.

Responses

- sugardog @flash.net 4/14/99 17:26

The RAIII manifold will fit a 6X head, but it may not fit your chassis. What RAIII manifold do you want to use (long-branch or short "GTO style"), and what chassis are you planning to drop this combo into?

Jerry Brock Bio 4/14/99 22:49

Website: http://www.boyleworks.com/ta400/psp/rebuild455jb.html

Gregg, I am running RamAir Restoration (Rage) repop manifolds. I have run them on my #64, #66, and my 6X heads. BTW, My heads flow 215 on the exhaust at .500 lift, with 1 3/4" headers. My RamAir manifolds (2 1/2" outlet), Gasket matched and flash ground out, flowed 195 @ .500. A set of Generic 3 tube headers flowed 179 on the center 172 on one end, and 176 on the other end. So much for the theory that all manifolds are junk!!! Jerry

- tony 4/15/99 5:56

what is there phone # or e-mail ? I want to get a set of long branch for my bird...

- Tim Baker ..\members/html/65.html

..\members/html/65.html4/15/99 9:16

RA Rage is 800.421-8455 / 817.421-5375. I'm running these on my 65 and I really like them, they hogged-out collector from 2.25" to 2.5" for me for a little more flow. I used POR-15 exhaust gray and it seems to be a good product. Jerry, I think that's first time I have seen actual flow numbers on these, thanks for the info that's great !

Jerry Brock Bio 4/15/99 22:32

Tim, Those numbers were on my heads, and the flow numbers were what the flow was on my heads, but they were back to back and were Apples to apples. Tuning does enter in to the equation. Flow is just one part, but it is relative between the different sets of manifolds. Jerry

Topic: 7917

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- 6X head value - Glenn tripower455@compuserve.com ..\members/html/35.html

..\members/html/35.html4/18/99 7:39

I was at the local machine shop discussing my 455 rebuild with the machinist. I was going to have my 114cc 4X's done (magged, cc'd pressure tested, milled .060, new thin walled guides, new ss valves, springs retainers keepers, spring pads milled, 3 angle valve job etc). The guy has a set of 6x-4's, that were ported by Jim Taylor years ago, have new s/s valves (1.71" 351 cleveland exhaust) they c/c out at 95. They were used on a 400 for about 5000 miles and have been sitting ever since. He wants $700.00 for them. Is seems like a good deal to me. The machine work plus parts for my heads will cost more than that. He showed me the flow sheet provided by Jim Taylor, and it was pretty much greek to me, insofar as I have nothing to compare it to. I don't know how they compare to stock regarding flow at various lifts. Maybe OMT himself can shed a little light on this! The heads are for a 74 yy 455, 66 tripower, reproduction RA headers, M-20, 11" clutch, with a fairly tall rear (currently 2:73 open, 8.5 corp 10 bolt), I am going to change the rear gears out, to either a 3:08, 3:23 or 3:42. Cam will likely be the Summit 2802 224/234, 465/488. Any comments?

Responses

Jerry Brock Bio 4/18/99 9:43

Is that Jim Taylor (Pennsylvania) or Old Man Taylor (Jim) from California that did those heads? Big difference there!! OMT is the good guy here!!! Jerry

Tim Baker Bio 4/18/99 9:52

hi Glenn, a 66 GTO/455trips/4 spd sounds great!! traction is going to be a problem, plan on posi with that gear swap. IMHO I don't think these heads were done by JIm "Old Man" Taylor, I suspect these were done by the Jim Taylor east coast engine builder you see in High Performnace Pontiac,not Jim "Old Man" Taylor from Califonia with the killer 64 GTO featured on Bill Boyles site. The 6x-4 head price sounds high to me, as soon as a head has been run even 5k miles value drops, but it may be a better value for you now than doing yours, my opinion I think you could shop around and do better if you have the time.

- Glenn tripower455@compuserve.com ..\members/html/35.html

..\members/html/35.html4/18/99 11:40

Thanks for the replies! Sorry for my ignorance! I apologize if anyone was offended! Imagine, 2 Jim Taylors who build Pontiacs! I believe that these are from the east coast guy, but I didn't even think to ask! These heads have around 5000 miles on them since the porting was done. The valves, springs, valve job, are new. The prices for machine work on my 4X heads are: $185 to mill the head decks and the intake side to match, 150 for the valve job, 96 for the thin wall guide liners, 25 for magnaflux, 60 to pressure check both heads. This is all minus parts, so another 160 for valves, 75 for springs, whatever the retainers/keepers cost. Plus, they aren't milled .060"! The total cost of doing my heads will be around 800 bucks. I can get a set of 6x #8's at a local Upullit yard for $80.00. It would reduce the milling costs by half, but would be made up for by the 80 buck purchase price!

Jerry Brock Bio 4/18/99 18:48

The -8 heads would have to be milled also. If the 6X-4 heads are fresh,the $700 is a bit steep, but not out of sight. I would try to talk him down. The cams that Summit has now for their 'House Brand' are Crane. They were Wolverine before. With the 4-speed, you wouldn't want any higher than a 3.42. You will have to have a strong clutch to hold the 455. For the street it will give you good all around performance. As Tim Baker mentioned, you are going to have a traction problem. There are several posi units available for that 8.5" rear. You will also probably want to box your rear control arms, or use aftermarket SSM or Hotchkis. Also a stiffener between the upper control arm mount and the lower mount. For the track, AirLift bags with individual filler valves will help you adjust to the track. Again, with that much torque, traction will be a problem. Jerry

- Glenn tripower455@compuserve.com ..\members/html/35.html

..\members/html/35.html4/18/99 20:17

Jerry, Thanks for the reply! Regarding the rear, I am not keeping the 7:73's, nor am I leaving it open. I am putting an Eaton clutch posi in it, I just haven't decided what ratio, but it will most likely be 3:08, since I do a fair amount of high speed driving. I want to drive it with the 2:73's just to see how it feels. I have a feeling that traction will be a problem with this beast even with a posi! I have already boxed my rear lower control arms, and have the frame reinforcment brackets (I think you can see them in the picture on my member page). I am going to use a Centerforce clutch, with my Hays 11" flywheel. I can't think of any stronger way to go. Any suggestions? As far as the head situation, after reading a few posts about 6x's, I learned that what I thought was a mismatched pair of a #4 and a #8 are actually both #8's. I was looking at a casting number on the end exhaust port that said "GM 4" and the other said GM 8 or something. I ASSUMED (I know, I shouldn't do that!) that they were the numbers signifying the application as has been discussed arounbd here. I am going to use them, with new guides and about .030" cut from the decks. It will still be pretty close to the price of the guys 6x's, but at least I will put the first mile on them after the machine work! When did summit change cam supliers? I thought that they used wolverine? Are the new ones similar, at least in profile, lsa, duration/lift etc? After e-mailing with Jim H a number of times, I pretty much came to the conclusion that that was the cam for me! I had a 744 clone in my old '66 GTO (389 tripower, 4spd, 3:90) and I liked where it made it's power. I realize that gearing had something to do with it, but I figure that the extra 73 CID will make up for some of that, plus I am a bit more knowledgeable (thanks in a big way to you guys here on the site!). Thanks again for the help!!!!!! Glenn

geebjen Bio 4/19/99 11:24

Wait a second. When did summit change their house brand cams? Are they still run to the same specs as the old Wolverine or to exostomg crane cam specs?

geebjen Bio 4/19/99 11:37

Wow! How did I type "exostomg" when I meant existing? (That was a rhetorical question, no need to answer).

Topic: 7930

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- 6X THANKS!!!!! - Glenn tripower455@compuserve.com ..\members/html/35.html

..\members/html/35.html4/18/99 20:24

To ALL you EXTREMELY knowledgable pontyackers!!! Thanks to this board, I didn't go and buy another set of 6x heads for my 455. I have a set that I thought were a mismatch of #4 and #8, but I was looking at the wrong #4 and #8! I did a search of the q&a on 6x, and one of the responses told me that I was looking at the wrong number. I didn't know about the little machined pad between the plug hole and the valve cover rail. I went out to the garage, and with a little paint stripper found 8 on both! I was looking at a cast number on the end exhaust port! Thanks again!!!! Glenn

Topic: 8043

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- 6X-4 or 6X-8? - tomas tr_marshall@prodigy.net 4/24/99 2:06

what is the difference between the 6X heads and how do u indentify what u have? would the 6X heads work on a 455?

Responses

Jerry Brock Bio 4/24/99 10:28

The 6X heads are easily identified by a stamped(not cast) numeral 4 or 8 on a vertical pad to the right side of the head, as your looking at the head from the exhaust side. I now have the ^x-4 heads on my 455, and they are great. There is some discrepancy as to the actual cc's of these heads. The 400 -8 heads are listed at 101, and the 350 -4 heads are listed at 92-94. Mine cc'd at 95 - 97 cc with some minor valve recession. With new valves (1.77" exhaust) they cc'd at 94 cc. We took a clean-up cut on the heads, and they cc'd at 92 cc. I hope that helps you. Jerry

jb69fb Bio 4/24/99 13:51

Tomas; Jerry is right, I foud That #4 400 heads are 101cc and #8 is 98 cc, my # 8's cc @ 98 cc, Does not mean they all are.

KK Bio 4/24/99 20:57

Whats so special about 6X heads? (maybe I should know but I don't). Are they easily ported or something? Wouldn't you have to put the bigger exhaust valves in them to make them work good? The 101cc combustion chambers seem kinda big to me. Comments?

- 4/24/99 21:07

KK, they are plentiful, will put a 455 into the 9.5 : 1 compression range and were designed to run on unleaded.

- rob whitaker rob455@aol.com 4/25/99 19:18

I am using stock (unported,1.66 exh.)6x-4 heads on a 455 in a 4200 lb. CanAm. I ran a 13.2@102. on radials.They die out up top,but the low and mid range is pretty awesome. I can't wait to port them!

Topic: 9361

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- 6x Heads - Headers... - Samuel 6/22/99 1:44

i have a weenie 400 w/ 6x heads, but it has headers on it that are rust free and look pretty new. I know that the 6x was lacking a little on the exhaust side.. just wondering what other heads these headers will bolt up to?

Responses

engo Bio 6/22/99 5:49

all other D-port heads

- JerryH lanier@vivid.net 6/22/99 12:31

Dont be so down on your "weenie" 400. That motor has a lot of potential that could make you really proud. Not everyone can afford the stuff it takes to have a car that people fear (me included) but a pontiac is easily modded to become a very fun driver because of all the torque...and a fun car is what its all about

Steve Chin Bio 6/22/99 13:42

400 is "weenie?" Since when? (OK, stop laughing guys, I know I was brought up with the "little" Cadillac engine at 427 cubes...). These days, the automotive press calls the "Corporate" 5.7L engines "large" or "big" at 350 cubes. 400s have a lot going for them - just build it with design parameters in mind that allow you to rev it more freely than a 455 would be revving and gear it accordingly. It is fully possible to strike fear into the hearts of the unwashed masses with a 400.

TempesT68 Bio 6/22/99 13:45

for sure! i and many others feel the 400 and 428 are THEE engines for pontiac, if you see the fastest stock running ones were 400's the 455 is a good streeter, but its the un-revability that start to catch up to it.

- Samuel 6/22/99 15:36

It's weenie compared to just about everything else we run out here. our Ford F250, 460 is built to over 550 ft/lb of torque at about 3500rpm. My bonny sits at 303 horse completely stock .. the Audi has a turbo... its (the 400) a 2bbl, 6x heads, less than 8:1 compression. i know 400's can be built... but this one is just weenie :)

Steve Chin Bio 6/22/99 17:52

Shoot... I typoed there... The "little" Cadillac was 472 cubes!

Witchdoctor Bio 6/23/99 14:16

Hey, I love my daily driver `76 400 T/A 4-spd., with 3.08 gears. With nothing but dual exhaust, early intake, and careful tuning, it will still out pull 90 percent of the cars I run across in the 50-100 mph. range. OK, I'm lying just a little bit. I did do a little port clean up when I freshened up the engine at 115K., but it is still much more fun than my wife's newer T-Bird or the pickup. WD.

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Topic: 9552

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- 6X-8 vs 6X-4 - RCA sporter@mail.cybertron.com 6/29/99 23:11

Is there any significant difference in flow between these two heads? I have a set of each and its time to choose one set for my 455.

Responses

TempesT68 Bio 6/29/99 23:40

use the 6X-4's they flow better

- Bob Dillon 6/29/99 23:53

but watch your deck clearance, the chambers are smaller and they'll make higher compression.

76 Enforcer Bio 6/30/99 7:20

I thought flow between the two was the same, but the chamber volumes were different. 91-94cc's on the 4's and 98-101cc's for the 8's.

Witchdoctor Bio 6/30/99 12:29

I have yet to see any verifiable difference in flow between the two heads. I do not like the #4 on the large bore of the 455 due to the excess amount of flat head surface (and sharp edges) hanging out in the non-squish side of the chamber. Just my 2-bits. WD.

- Brian Baker bkbaker@att.com 6/30/99 19:24

Flow between the two should be pretty darn close, since bowl design and port volume between the two is the same. The "8's" just have a larger chamber (mine measured at 98 cc's). The "4's" would be a better bet with their average chamber volume being about 92 cc's. My "8's" gave my .030" 455 about 9:1 CR with 98 cc's of chamber volume. I just had .060" milled from them and my volume is now 86 cc's (for about 10:1 CR).

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- 1.77 valves worth it in 6x-4? - gregg 6/30/99 15:52

I'm going to be buying new valves for a set of 6X-4 heads that will go on a street 400 with a 4 speed. The cam is 224 and 230@50. The shop only whats $25 to put the larger valves in. I want a fast street machine but dont care about the strip at all. Should I get the 1.77 or not?

Responses

padgett Bio 6/30/99 17:50

$25 with hardened seats ? Opening the 1.66 up to 1.77 will remove what hardening the factory put on and the exhaust is where you need it.

- Brian Baker bkbaker@att.com 6/30/99 19:45

In most cases on street/strip engines, you won't notice any difference between the 1.66/1.77's. I've yet to see any printed tests that indicated the larger valve was an improvement. Porting may bring another variable into the equation altogether. For a mild rebuild, it probably wouldn't give that much more performance as the throat of the exhaust bowl is coordinated in size with that of the valve. You would need to enlarge teh throat area in the port to take full advantage of the larger valve. If none of this makes any sense, I would suggest reading anything penned by Pete McCarthy on the subject.

- Brian Baker 6/30/99 19:46

My previous post was in regards to the 6X head, not the earlier large valve heads

- gregg 6/30/99 22:53

Why did Pontiac change the valve size anyway?

Witchdoctor Bio 6/30/99 23:44

Why did Pontiac go to the 1.66" exhaust valve across the board in 1973? What happened that same year? Active EGR for emissions requirements. What was the only Pontiac engine in 1973 that maintained the 1.77" exhaust valve? The SD-455. This should to tell us something. Add the cost savings of supplying the low performance exhaust valve on everything from the bean counter's perspective and you have the answer. Who am I to argue with the works of Pete McCarthy? Well, I was porting BMC heads for SCCA racing while Pete was making his bones in NHRA stock and super stock class racing, where head modifications were strictly forbidden. I kinda think that Pete really first got into head work with his articles in HPP in 1991. All enthusiasts evolve, and I'm sure that he would be the first to admit, that some things committed to print can be shown lacking with time and further development. There was a good thread recently concerning roller cams, where flow results for some of the better running engines were published. Did anyone note the E/I ratios on Bill Boyle's heads? Mid to high .80s. Blowing smoke about flow numbers, it is easy to sometimes lose track of the difference between the requirements of intake as opposed to exhaust flow. The velocity and mixture consistancy of intake flow with regards to torque production gets a lot of play, BUT, if you cannot evacuate the cylinder on the previous exhaust stroke, intake flow, velocity, and mixture strength is wasted. I have yet to see a production Pontiac head with the 1.66" exhaust valve get out of the mid .60 E/I ratio range. The RA-II head, with the standard size intake and the large exhaust could reach the high .80 range, while the RA-IV heads would reach mis .80s. The standard E-Head, while assisted by a high exhaust port floor and exit, will still show only approximately .75 E/I ratio, by their test figures. Look around. Is any of the really heavy hitters running the E-Heads keeping the 1.66" exhaust valve? From what I have seen with the stones, the actual hardness of the induction hardened seats of the small exhaust valve production heads is so minimal that it is not worth consideration. The need for hardened seats, that was such a big deal during the 80s has proved to be of little conquence unless you are running flat out for miles on end. Installation of the 1.77" exhaust valve in a 1.66" head does require a little thought and more machining than I can believe can be accomplished for $25, however. Both the 6X and the earlier performance heads have the 90 degree drop down bowl directly under the seat. If this area is not duplicated, and the resulting bowl blended into the casting, the advantage of the large valve will be lessened. Just cutting the larger seat is easy, but you have to go the whole nine yards. FWIW. WD.

- R 7/1/99 12:54

I agree with WD and Brian and $25 sounds very cheap for cutting larger valves. I inquired about this for my 4X heads. I wanted to slightly mill them for more compression, and also add 1.77's - A very reputable machine shop that I have had grea results with baiscally refused to take my money to install the larger valves. Theres no way you would ever notice a difference, especially on the street. Get the best 3-angle you can and have them slightly ported/cleaned up.. Hard earned money better well spent.

- Brian Baker 7/2/99 20:10

And keep the seat angle on the intake at 30 degrees!!! Alot of "Chevy" machinists will try to talk you into a 45 degree seat, don't let 'em!!!

Topic: 9924

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- 455/6x MPG - gregg 7/18/99 10:52

just checked my mpg of 455/6X auto with 2.56 gear. (12.3 mpg) anyone else running this combo that has checked?

Responses

joe B Bio 7/18/99 11:15

What size cam are you running?I get 15 mpg in my 455/6x with summit 2801 with 3;23 screw and ran the 1/4 just last night in 14.4 with my brother in law (1st time racing) behind the wheel. And the temp was a sweaty 90degree with 90 percent humidity.

Jerry Brock Bio 7/18/99 12:31

I am running my wagon with the 6X-4 heads, a 230/236 CompCams hydraulic roller, Performer RPM, and a Q-jet. The car has a 3.42 gear and a TH350 transmission. Last Sunday I made a trip 268 miles round trip and used 18.78 gallons. That was with the A/C on, and the cruise set at 75 mph, and with cars passing on both sides (Michigan drivers) I pushed to 80 - 85 for a few miles. That figures to 14.27 mpg. For Tony deFoster's benefit, Dave Bennett and Linda were there when I filled the tank, and can verify the mileage. The car ran 12.678 yesterday at Milan Michigan, in 92 degree heat. Jerry

- gregg 7/18/99 13:58

Im running an 068 cam

georgew Bio 7/18/99 14:12

Just finished driving my 455/6X '76 GP from Mass. to TX. Averaged about 14.8 mpg @80 mph. I have 2.41 gears and a stock torque converter, and it was jetted on the lean side. Definitely losing some economy to the RAIV cam, as well as all the power below 3000 rpm. Don't use this cam in a heavy car!

- Lee ..\members/html/455.html

..\members/html/455.html7/18/99 16:52

I ran a 6X/455 w/2.73's. Fully loaded, A/C-equipped '79 T/A. It average about 12.5, and would break into the 14's on long highway cruises. Erson TQ30 cam, and best e.t. of 13.2 @102.

- RCA sporter@mail.cybertron.com 7/18/99 17:47

'67 Fbird with 455/6x-8/068&1.65/Q-jet/2004r-auto/3.55s. Average 19.5 mpg at 75 mph. In the process of switching to 041/rhoads/Holley 750/Ferrea SS valves and some minor porting. Will probably lose a little mpg, but who cares!

- Bob Dillon 455Pontiac@Netscape.net 7/18/99 17:51

I got about 14.5 on a 90-mile trip last weekend. '72 Grandville, 455/6X, headers, Edelbrock 1406, 204/214 cam, 3.08 rear end. Not too shabby for a 4500 pound car.

Steve Chin Bio 7/19/99 17:49

I haven't run 6X heads, but with 2.41:1 rear gears, #64 heads, and a 067 cam (and a single plane intake) I got ~20.4 MPG on a couple of occasions. With the E-heads, 2.56:1 12-bolt, and 041 cam, I get ~15-16 MPG if I can keep my foot out of it (not likely).

- HR 7/19/99 20:27

Jerry, I noticed you are running the 6x-4 heads on your 455. I am running the 6x-8 heads, but was thinking of switching the the smaller chambers. Do you have any pre-detonation problems with. What is your compression?

davem Bio 7/19/99 21:00

What the heck am I doing wrong? The best I've ever gotten with my '70 Firebird with a mild 400 and 3.08 gears is 12mpg. The engine has the following specs. 8:1 cr, Summit 2800 Cam (204/214, .420/.442 112 lsa), Perfomer intake, and a Holley 600cfm carb. It has nice power for what it is but I could never figure out why the gas mileage was so bad. I'm going to put it in a car with 2.73 gears and switch to a Q-Jet and see what happens.

Jerry Brock Bio 7/19/99 21:09

HR, I have 9.75 cr.(92cc) and run 92 - 94 octane pump gas. The dyno pulls were made using 93 octane Citgo pump gas. As for mileage, a Holley is a good performance carburetor, but will never give gas mileage. A Carter/Edlebrock is a little better, but still will not equal a Q-jet in mileage. Believe me, I have tried about every possible combination of Holleys, and several Carter's. I have about 6 different Holleys, jetted for different setups. I don't knock Holleys, I just don't use them for the street. Jerry

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- 6X heads/stamping #8 - tbligh Bio 8/5/99 21:13

I have found a set of 6x heads available for purchase cheap. I am told they are the "good Ones". Does anybody know if the #8 stampings on the 6x heads signify something special? I am contemplating buying these, as I have been led to believe they are superior to my 4x(press in studs) currently on my motor. I have accessed various sites, books and such, but have found nothing about a #8 stamp. thoughts, ideas, or direction appreciated. thanks, tom

Responses

Steve Chin Bio 8/5/99 21:28

There are two stampings on the 6X heads, the #4 and the #8 stampings. The #8 stamping heads were found on low-performance 400s. The #4 castings were found on 350s and the L78/W72 Hi-Po 400 of '77, '78, and '79. The main difference is combustion chamber size (~99cc on the #8 vs. ~91cc on the #4). Are they superior to your 4X heads? Depends on which 4X heads you have. Since they are pressed-in stud heads, I would venture to guess that on the virtue of having screw-in studs, they are superior. If you have a 455, they are probably superior in that the 455 4X heads had HUGE combustion chambers (on the order of 124cc).

- Chris lewisck@whidbey.net 8/5/99 22:54

Just a note, I know Steve, and John W. have been doing a lot of research, but I know for a fact that the #8's were also put on the 79 L78/W72 motors. I have one, and have seen atleast one other 10th Anniv. 400 with these heads, they are nice. I believe that in 79 they used whatever heads they could get to put on the last of the 78 400's, so I believe some had the #4's and some the #8's. Again just a note, not trying to step on anyone.

- Eric D. douthitt@wauknet.com 8/5/99 23:18

The '75 &'76 455 with 6H heads had the 124 cc chambers. A 4X, 455 head will be around 114 cc's. Eric D.

LeMan Bio 8/6/99 8:18

I thought that folks around here concluded that the chambers had to be measured to determine if the heads were 6X-4 or 6X-8. Where is this #4/8 stamping?

WarrenK Bio 8/6/99 10:14

#4 were believed to be used on the 350 and the #8 were believed to be used on the 400s. I have a set of both and the chambers on the #4s have a smaller diameter. There have been discussions about the pros and cons of using the smaller chambered heads #4s on a 400 or 455 block. Obviously the smaller cc would yield a higher/desireable CR, but several people (I.E. Witchdoctor) say that by using the smaller chamber on a larger bore is not recommended due to the chamber "ledge" overhanging the bore. There are other "schools" of thought just claiming the opposite. I would like to hear from both "schools" to find out their views if the "ledge" created by the smaller chamber used with a larger bore block is good or bad.

WarrenK Bio 8/6/99 10:25

LeMan the 4 or 8 stamp is on the accessory mounting boss.There are two accesory mounting bosses per head. The stamp is on the front boss just above the mounting bolt hole. This is from memory, I'll verify when I get home.

- John Witzke mwitzke@prodigy.net 8/6/99 17:40

Chris, I find this intresting because I have examined several 1977,78,79 "W72" motors all had the 6X #4 heads. All 1979 "W72" optioned cars were made with left over motors produced in 1978. My 1977 11,000 miles factory original Trans Am has the 6X #4 heads. Steve is right on the money with the CC's for the 6X #8 and 6X #4 heads. The #8 were 98-101cc's and the #4 were 89-91 cc'c. Chris I would like to ask a couple questions. First, are you the original owner of your car? And second, Is the motor original with matching numbers? No rebuilds, nothing replaced?

- John V. 8/6/99 21:38

I remain unconvinced that Pontiac assembled the motors for the '79 W72's during the '78 model year. The block castings were left-over, not the engines! '79 W72 were assembled right along w/ other '79 engine production and assigned motor unit nos. upon assembly during the '79 model year. I don't doubt what Chris has posted about the use of the heads. I haven't seen firm documentation, but there has even been some suggestion that the blocks used up in '79 may not even have been all the same casting p/n's. It is very possible that Pontiac was cleaning out the attic to assemble the last of the 400 motors. If they had a bunch of 6X-8's there was no point holding them back.

- Chris lewisck@whidbey.net 8/6/99 22:29

I am the 3rd owner of my car, and the other 10th is a 2nd owner car. The second owner bought it in 1981, and had done nothing but standard maintenace to the car. I just completed a rebuild on the engine and the machine shop said the engine had never been reworked. I could see the possibility of one vehicle having head problems and having them replaced with a different set, but two cars being replaced with the same heads. Both cars numbers matching. I would be amazed if it happened. I believe that the heads on both are original. Its amazing how a little thing like this can cause such a big discussion. Before I rebuilt mine, people had me believing I had #4's on it, but when I looked closer I had the #8's and thats when I checked my buddies 10th and found the same #8's. Hope this helps John.

Topic: 10484

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- 76 350 6X heads - tom bounty5@earthlink.net 8/9/99 7:16

In my junkyard travels, I have come across a set of 1976 6X heads from a 350 FB. In previous messages to this board, I have found that these "350" 6X heads have a smaller combustion chamber than the 400/455 versions. My question is: would the 350 6X heads offer a performance advantage over my current 4X(press in studs) on my 73 Y4 400. I seem to recall something about "overhang" when using the smaller 350 heads as opposed to the 400. any ideas, anybody? tks, tom

Responses

67 GOAT Bio 8/9/99 11:09

If I remeber correctly, the 4xs you have on your 400 are rated with 98cc chambers. The chamber sizes for the 6xs you are refering have seem to be a grey area. I have heard on this board of volumes as low as 89cc and as high as 98cc. I have several pairs of these heads and havent had a chance to accurately measure them, so, considering the chamber sizes I dont think you will see a major compression ratio difference. Therefore, I doubt that you will see much "performance advantage" by simply swaping the heads. Now, if you were to port/polish the 6xs, or simply smooth up the 6xs I would think you would see a slight performance advantage over the 4x if worked similarly. Again, there probably hundreds of topics on this site in the archives on the 6xs that you might be interested in. Search back and read on. I have heard people bless the 6xs with RAIV capabilities. Either way, Good Luck.

- John V. 8/9/99 14:39

The 2 bbl 400 Y4 probably has the 4H stamped 4X head. If so, they have 1.96/1.66 valves. See post 6679 for info. The 4 stamped 6X head on a 350 has 2.11/1.66 valves. 67 Goat is right about the chamber sizes being pretty similar. I don't see any point to just bolting on the 6X heads. Then again I don't see how a worked 6X has any edge over a worked 4X. What is your goal?

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Topic: 10544

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- 6X head milling - jv jv4magna@erols.com 8/11/99 10:52

Does anyone know the maximum amount that 6X(101cc) can be milled?

Responses

geebjen Bio 8/11/99 11:16

I know only what I've read here, that you should not mill any Pontiac Head more than .060 inches. Anyone else?

- Don 8/11/99 11:26

i have seen 120 taken off

Jerry Coffee Bio 8/11/99 13:28

Mill that much and you will stand a good chance of warping the head when it gets hot. A cut of .060" is the max.

Witchdoctor Bio 8/12/99 19:49

Me Too. If I can't get the job done with a max. of .060", I'll look for another avenue. WD.

dsm Bio 8/13/99 12:41

The chart in Pete McCarthy's book says that the later d-port heads should only be milled about .050...Dont have the book handy or I would be more specific. On my 6Xs (which measured out at 98-99ccs), I went .045 on the head and intake surfaces and have not had any problems (3 years and counting). I know other people have gone .060 with these heads, but I chose to be a little conservative.

Topic: 11014

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- 6X Heads - preacher Bio 8/30/99 11:53

After tearing down my 400 engine. It seems will need complete rebuild. I am the one who had the "092 heads" I have since found a rebuilt engine with 6X heads on it for less than what a rebuild will cost me. This is from a parts house that a friend bought for a restoration in a firebird. He was told the warranty would start when the car was put on the road. So much for honest parts house people. Anyway my friend bought the guy a new engine so he would have a warranty and now he needs to sell this one. The volume on the 6X heads is 114 which is pretty big. I am building this for my son as well as myself and performance counts but not in the extreme. What about the 6X vs 092 heads.

Responses

67 GOAT Bio 8/30/99 12:53

I think the 092 heads are closed chambered heads most likley from a '66 389 and have a relatively small chamber size, 70cc I think. It will probably give your 400 a high compression ratio in the 10.2:1-10.5:1 neighborhood. Which, depending on your set up, might be high for a performance pump gas engine. Not saying it isnt possible. I personally would make a trip to as many junk yards as possible and try to find a set of 6x-4s off of a 350. They are still plentiful. A set of 6x-4s and a slight mill you could get into the 8.5-9.5:1 compression ratio neighborhood, which would be ideal for pump gas and still make some good power. Everything depends on the rest of the combo; intake, cam, exhaust, heads. If you have to choose between the 092 heads and the 6x-8s, I personally would go with the 6xs which I think are an excellent head that would give you room for upgrades in the future. My .02. Lets see what the experts say.

David Holmberg Bio 8/30/99 13:07

I agree that you need to find a set of 6x-4's, I saw 3 sets at norwalk for $50. ea. they also have hardened exhaust seats for unleaded gas. The 6x heads flow as well as any other good d-port and if you do a minor clean up (gasket match-some are terrible) they will work great.

Jerry Coffee Bio 8/30/99 13:49

Before you chose the 6X-8 heads you had better think about it a little more. The 6X-8 heads have a monsterous 114 CC combustion chambers giving 6.8:1 CR on a 400 engine. The 1966 #092 heads have 67 CC chambers giving too much for pump gas at 11.22:1 CR. Even the 6X-4 heads with 101 CC chambers only provides a miserable 7.66:1 CR. Even if you mill the 6X-4 heads .040", it will only bump the CR to 8.20:1. That is why a 400 engine is difficult to get an ideal CR of 9.5 to 10.0:1 to use with pump gas with the heads that are available. The damned 93 octane pump gas is just not made for 400 engines.

- John V. 8/30/99 14:18

If 114 cc, those heads would have been from a 455. Supposedly some late '75 455's used a version of the 6X. It has a secondary stamped code. The 400 6X was stamped 8 usually about 101 cc's, the 350 (& W72 400) 6X was stamped 4, about 96 cc's. Any chance you'll luck into a 455 with this engine? Don't give up on it til you check it out.

mr6x Bio 8/30/99 14:48

I agree with John, those heads must have came off of a 455. Too large of a chamber for a 400. The 092 heads should come in around 70cc's. That will give you around 10 to 1. If I had to make a choice I would rebuild your current engine and stick with the 092 heads. When they remanufactured that other 400, they probably assumed that all 6x heads were alike and threw those heads on it. Would you buy an engine from a builder that does not know these differences? I certainly would not.

David Holmberg Bio 8/30/99 14:53

My 6x-4's CC'ed out at a tick over 92cc. For a 400 there is no magic head for 9.5 comp, if you can find a set of #64 heads(70 455) great if not I would use the 6x-4's for a street car.

davem Bio 8/30/99 15:12

I thought the 6x-8 was 101cc and the 6x-4 was 92cc

preacher Bio 8/30/99 15:19

I think I'll buy the rebuild as the motor ran good in the firebird and only has about 200 miles on it. For $650 with new pistons cam head rebuild. I only know it is a 6X I got the cc from the head page in restorations. This is showing my ignorance I know but What is the diffrence in the 6X-4 and 6X-8. These heads had 6X and a 7 on one of the ports if I remember right and had E028 on them.

- jv 8/30/99 15:21

According to Pete McCarthy, the 6X-8 measure 96cc and the 6X-4 measure 91cc, which is close to what Dave says. I have seen the 101cc figure tossed around, but has anyone actually cc'd a set of 6X-8 or 6X-4?

geebjen Bio 8/30/99 16:07

My 6X-4's of unknown history cc'd at 93.

Donnie Ray Bio 8/30/99 16:13

I cc'd mine. 6X-8's were 98cc before cutting them.

- John V. 8/30/99 16:39

All '73-'77 350 motors were rated 7.6 cr, ('74 GTO maybe excluded). AFAIK, all 350 heads thru this period were designed to be nominal 96 cc. Many 400 motors were rated 8.0, had nom. 98 cc chambers. Some later versions were rated 7.6 cr, chambers on these heads were nom 101 cc's. The external secondary code is a small no. stamped on the face of a rib just below the valve cover lip on the exh port side of the head. I suspect the 7 you report is a large cast character which would indicate a foundry line. The code you're looking for is a small stamped character. Since actual cc's were subject to the tolerances of machining, you have to cc any head to know what you really have. The 6X-4 was different from other 350 heads in that it had the 2.11 int valve like the 400 head but a smaller diametric cut on the chamber than the 400 6X-8 head. For reasons unexplained, it seems Pontiac boosted the advertised cr of the W72 motor from 8.0 ('77) to 8.1 ('78). Not sure if the chamber vol changed.

Witchdoctor Bio 8/30/99 18:31

Virgin set of 6X/8s were also 98 CC.s. All of the 75-76 455s I've seen have had 6H heads, which had huge chambers around 120 CC.s. If your rebuilt 400 is .030" on the bore, I'd cut the 6X/8s .030" for a nominal mid 8 static ratio, and enjoy. WD.

Jerry Brock Bio 8/30/99 18:55

My 6X-4 heads were right at 95cc with mild valve recession as removed from the 76 350 engine. After a fresh valve job, new stainless valves (1.77 exhaust)and just a clean-up cut, they cc'd at 92 cc. Jerry

- J. Witzke "Mr. W72" mwitzke@prodigy.net 8/30/99 20:09

The W72 6X #4 heads were the same from 1977 through 1978-79. Both have approx 89-91cc's. According to Pete McCarthy the actual compression ratio of the W72 motor from the factory was around 8.6:1 to 9.0:1, not the advertised 8.0:1 or 8.1:1.

rob455 Bio 8/30/99 23:30

I have had great success running 6x-4 heads on my 455. They are off a W72 motor. they are untouched except for a valve job. 13.20 @ 102 in a 4200 lb. car. They cc'ed at 91, I know they have been milled at least three times. I can't wait to see the results when I open the ports up.

Topic: 11114

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- 6X 0n 326 - Tony 9/2/99 21:35

What are the benefits of installing [350]6X heads on my 326 [1967].I'm loking for less compression,and better gas mileage.

Responses

Johnathan Bio 9/2/99 22:07

you will get less compression, thats for sure

jb69fb Bio 9/3/99 5:26

I calulated 7.23 to 1 CR , Go to (RESTORATION) and than to COMPRESSION CALULATOR , Type in your info and see what you come up with , there will be no power gain by using these heads , they make thicker head gaskets try that first , What is wrong with your heads now ? cost of 93 octane ?

LeMan Bio 9/3/99 8:24

For best mileage you need the most compression your engine will tolerate. The stock 326 2bbl heads should give you about 9:1 which should be close to optimum. I never had any detonation problems running 87 octane gas in my 326 2bbl and i got 23 MPG on the HWY. What are your experiences(detonation, MPG)?

davem Bio 9/3/99 12:50

I wouldn't be surprised if your compression was even lower than what was previously stated. I'd guess it would be in the 6:1 range.

Topic: 11309

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- Valve size 6X (4) and 7K3 - Eric K Bio 9/11/99 23:36

I want to try and use the valves and springs from my 7K3 heads on my 6X (4)'s. Can anyone here confirm the size between these two heads, on both intake/exhaust. Thanks.

Responses

- J. Witzke "Mr. W72" mwitzke@prodigy.net 9/12/99 8:24

The Valve size for the 7K3 heads are 2.11/1.77. The 6X #4 is 2.11/1.66

Jerry Coffee Bio 9/12/99 8:56

The intake valves of both heads are 2.11" but the 6X-4 heads use 1.66" exhaust valves and the 7K3 heads heads use 1.77" exhaust valves. You can install the larger valve in the smaller valve head with some machining of the seats. The valve springs are the same for both heads but the length of the valve will determine the spring fit. The depth of the combustion chamber usually determines the stem length and there is only 5 CC difference in the two chamber sizes, so they may be the same length. The valve length for the 1972 7K3 heads is 4.960" but I have no information on the length of the valves in the 6X-4 heads. Maybe someone else can address that.

Topic: 11505

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- 96 or 6x heads on a 455 - dan streetmetal@webtv.net 9/19/99 16:25

I am building a 30 over 455 with a 068 cam stock intake and quadrajet carb .this is going in a 66 grand prix with a richmond six speed and a 3.08 gear. is there any advantage to either head?does the 96 head have hardened exaust seats from the factory.any info would be appreciated thanks dan

Responses

jb69fb Bio 9/19/99 18:42

Dan : # 96 heads are from 1971 GTO/Firebird 400 , they are 96 cc heads , harden seat I don't know . I computed 9.34 C.R. .005 deck height , .047 head gasket , .030 bored . I would use them . 6X are good , there are on my motor , I milled them to obtain 8.9 C.R .

- jeff jplatt02@snet.net 9/19/99 18:52

been there,done that. if i could have found 96 heads,i would heave used them.they seem to be a better flowing head in stock form.if your leaving them stock,i'd go 96s.on the other hand,if your gonna port anyway,6Xs are easy to get cheap!make sure the chamber size is what you want-they vary.ported,blended,with 2.11/1.77 RA IV valves ihad a decent pair of heads for about $800.00.6Xs have screw in studs guideplates,i just went with chevy 7/16 studs.flow was 250@25in.spending 5hrs.per head grinding.good luck!sleds are cool!

- jeff 9/19/99 18:55

oops! no,the 96s don't have hardened seats.you can have the shop add them,but most guys say for limited driving,don't bother.you won't pound a seat for a long time.their opinion.

Horst Bio 9/20/99 8:53

6X heads are dime a dozen, just make sure you get the 98cc 400 versions and not the 115cc? 455 versions. Other people on this board have stated that going to 1.77 exhaust valves is marginally worth it for a street car.

- steve tirebirner@prodigy.net 9/20/99 21:09

are th 96's 68's or 71's? If they are 68's with 72cc I'd use them.right combo and you can run pump 94 octane like I do on my daily driven 67' gto with 10.98 to 1 compression. good luck.

Topic: 12295

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- 72cc heads vs. 6X - Jim 10/22/99 22:22

Can 6X heads be machined enough to give enough performance to offset the larger combustion chamber over any of the 72cc heads? Would you buy machined 6X heads for $300, or would you buy Totally rebuilt #16's with a 3 angle valve job $450? I don't know what's all been done to the 6X's, but It seems to me that they would have to have an awful lot done to them to make up for the for loss of compression, is that true? I can also buy #62's that have been partially rebuilt for $300. They have some of the valves replaced, new valve springs, etc. Do you guys have any advice about which ones to buy? The guy with the 6X's apparantly knows a lot about motors and he said the 6X's were good heads but had to be used with a single plane intake manifold, does that make any sense to any of you? I'm leaning toward the #16's right now, but I'm having a hard time making up my mind. Thanks.

Responses

joe B Bio 10/23/99 2:13

and for the biggest factor governing head choice,What block?jo b

- Jim 10/23/99 14:26

Sorry,its a 400.

Witchdoctor Bio 10/23/99 20:14

Jim: We have bashed this question about many times, and darned near everyone has a different opinion. Here is mine. The #6X head has a beautiful intake passage. It was one of the controlled casting heads, and the intake port came out of the foundry with a near perfect gasket match. The deeper chamber on the intake side did not displace the short turn radius/valve seat position to a major degree, and at stock D-port intake port dimensions, it will flow as well as any. The problem lies on the exhaust side. The deeper portion of the chamber under the exhaust passage, moved the seat too close to the short turn radius, and most of the 6Xs have passive EGR bumps cast into the exhaust port just outboard of the guide boss. Couple this with the 1.66" exhaust valve, and you have a bad E/I ratio, which to a large extent, negates the positive features of the intake. The head has to do three things in order to make the best possible power. The intake port has to admit the largest possible amount oa air/fuel mixture, while maintaining maximum dispersal of the fuel droplets. The chamber has to maintain fuel suspension in all areas of the chamber cavity during compression, and provide a smooth, even burn, that converts the largest amount of the fuel into heat and pressure. The resulting pressure has to be applied to the largest possible area of the piston deck (F=PxA), and then the resulting exhaust gasses, which will not support further combustion, have to be purged from the cylinder, so that the process can start all over again. I know this is long winded, but unless you can actually visualize what is going on in the engine, you can't make it go faster. I will not even consider the 6X for any performance use without the 1.77" exhaust valve. And even with the larger valve, exhaust flow will be less than can be achieved with the small chamber head. Given this, you are faced with making a 400 live on street unleaded with a nominal 72-75 cc. chamber. My personal opinion is, it ain't gonna happen. Now you have two choices. Either enlarge the combustion chamber, or run minus deck height. By taking out the chamber to full gasket size, and providing the bore reliefs, which DO help air flow, and laying the rear (squish) wall of the chamber back to a 60 degree angle, as was done by the factory with the 061 head, you can pick up 5-7 cc.s. If you want to think about less than zero deck, each .010" in the hole will add approximately 2cc.s. You continually run into black and white opinions in this game, but nothing is really true, nor untrue. It is always a compromise of balancing the pluses against the minuses. WD.

joe B Bio 10/23/99 21:04

Go with the 72 cc,by the time you de-shroud valves, cut quench area back at an angle and match chamber to gasket you will raise cc.Iv'e done it to a set of #15 72 cc heads.but I also installed 2.11 intk and 1.77 ex valves. Chamber cc'ed 86 cc when I was finished. Cutting quench area back to an angle, was an experimental Idear I didn't think anyone else was doing.But anyways it was a postive mod.Any time an engine needs less ignition advance, the more efficient the flame front is. Anyways by making the same mods to the 6x heads will increase cc too much. Chamber mods are the thing of the future so why start out with a chamber to big in the first place,when you can start out with a smaller chamber and apply todays mods and still end up with more cr then the big chamber. The best heads for a 400 are the 72cc cleaned up to 84-86cc ,the best head for a 455 are the 86cc heads cleaned up to 94cc.This is for street gas applications.Alot of people don't take into account the drop of compression after chamber mods to a head that was giving them the ideal cr at first.Basicly it's better to make a smaller chamber big then it is to make a big chamber bigger. jo b

- J.Witzke "Mr. W72" mwitzke@prodigy.net 10/23/99 21:19

In defense of the 6X heads there is a 1978 Firebird Formula 400 campaigned by High Performance Pontiac running the quarter mile at 11.98's seconds @ 108 plus mph in NHRA M/SA and L/SA classes. The 400 motor in this car has 6X heads with 2.11 intake and 1.66 exhaust valves. What 6X heads are you looking at, the smaller chamber #4 W72 heads with 89-91cc's or the larger chamber #8 101cc heads?

joe B Bio 10/23/99 21:45

Mr w72 you've just got part of the story,remember there are alot of HPP readers here.Yes it does run 11:98 but why does it run that et?I'm sure it's not just the heads.How about weight? it has alot of chassi developement time. How many times did he break the drive shaft because of optimum traction.Yes he did it with 6x heads,but could of done same with any stock head.It's a good point Mr W72,but not a good comparison reason.

- J. Witzke 'Mr. W72" mwitzke@prodigy 10/24/99 11:21

With all do respect Joe B my intent was to let Jim know that the 6X heads have potental. The small chambered 89-91 cc "High Floor" W72 #4 6X heads milled .040 will produce approx 85cc's. Heads are only part of the puzzle, also need to know, manifolding, carburetion, camshaft specs, etc. While it is true the 6X head isn't as good as some of the earlier heads it was still rated by Pete McCarthy as the best post-1972 low compression head. In fact much talk about the 6X head as well as other heads can be found in the pages of Pontiac Enthusiast Magazine.

joe B Bio 10/24/99 16:15

I believe the original post was more focused on chamber volume. the 6x -4 only have 95-96 cc.With todays chamber technology they will most definitly need cleaning up to optimize quench and de-shroud valves.So with that, how many cc's do you think the 6x -4 will have then. By the way to compensate for head volume (because they could'nt be touched due to stock rules) that 11'98 engine was stroked.I know we all have our own opinions ,I'm just tring to deliver all the facts. I have no disrespect to anyone,but by the same token I can't let by me misleading infomation. there is enough of that already.jo b

- J. Witzke "Mr. W72" mwitzke@prodigy.net 10/24/99 21:56

Joe the facts are this. Mr. Pete McCarthy has established the 6X #4 head chamber volume at 91.11cc's. NHRA has established the chamber volume of the 1977-79 W72 6X #4 head @ 89.09cc's. I have no idea where you came up with 95-96cc's for the #4 6X heads as it is a gross error. I highly respect Petes knowledge and I tend to believe that the numbers he has established for the #4 6X heads are probably the most accurate. As far as 72cc heads are concerned the vast majority of pre-1971 (1967-70)Pontiac heads have 72cc's whether they were bolted to a standard 400 or Hi-Po 400's. My point was to let Jim know that the #4 6X heads have potential. If Jim really wants to get serious he needs to get a set of No.96 or No.722 heads.

- Brian bdevlin@stanford.edu 10/25/99 1:38

Jim- Go with the 72cc heads. I just put some 670 heads on my 400, and I'm happy so far (although it hasn't even been a week yet, and I've put on maybe 30 miles). The chambers were not enlarged, and they were only milled a tiny bit to get a flat surface. Taking into account the 6 or 7 cc's from the valve cutouts on the pistons, I should have 9.5-9.6:1 compression. I'm running 92 octane and haven't heard any knocking, although it will deisel when shut off. It think with trying different brands of gas, enriching the mixture and getting a 160 degree thermostat I'll be fine. The real issue with my engine is passing the smog test since these are closed chamber heads with huge quench area (maybe less knock, but certainly more hydrocarbons- maybe I can make use of my smog ports!).

- gregg 10/25/99 17:39

I had a pair of 6x-4's cc by my shop and it came out at 93.5, I dont know about valve jobs in the past but it did have .010 stamped on the head indicating it had been milled already

Eric D. Bio 10/25/99 18:13

Website: http://www.wauknet.com/douthitt

John, there has been some discrepancy on the cc volume of the 6X (4) heads. Bill Boyle did a little survey about a year ago and many owners reported various cc's. My set looked virgin from all indications and cc'd 95. It appears the volume may vary between 91-95 cc's. I have the deepest respect for Pete McCarthy as well, however, anything can and will happen in mass production. Additionally, the best personal performance I have seen from a 6X head is 11.80 @ 112 in a 3,900 lb. GTO. I have heard reports of much quicker times but as we all know, it's the total combination. Eric D.

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- 6X WHAT'S THE BIG DEAL? - buckman Bio 11/14/99 21:14

While reading various posts,mag. articles etc. etc. I keep noticing that a favorite and popular choice of heads to use are the 6x heads. Are'nt these the 75 to 79 small valve heads and if so why are they so popular in many rebuilds today? The only reason I can think of is that they are late model heads and therefore there must be a million of them around.

Responses

- Todd farland@cts.com http://www.pontiaconline.com/members/4

http://www.pontiaconline.com/members/411/14/99 21:24

You hit it right on the head. See, the 6x heads are indeed "workable" and can be made to preform. An added advantage is that the chamber size of the 6x-4 head works nice on a 455. The main thing is that they are plentiful and cheap. Soooo, if you're a big-shot engine builder selling engine conmbos, it make since to push something that's attainable to most everyone, rather than pushing combos using rare and exotic parts that only a few will ever be able to find/afford.

- gregg 11/14/99 21:43

Hardend seats,cheap,smaller exhaust valve is not a big deal for a street motor.

Jerry Coffee Bio 11/15/99 7:30

Hardened seats are no asset. Hard valve seat inserts are not needed and are a waste of money. Use 'em if only if your valve spring pressure is more than 125# on the seats and pump gas is going to be used.

jb69fb Bio 11/15/99 19:02

Not a big deal for a 350 cu in motor .

Topic: 12792

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- 350 – 6X Heads - JK 11/15/99 10:54

I am certain that this topic has been covered previously, but I can't remember on what post. My local Auto Wrecker (Pick A Part) has a 77 GP with a 350 and 6X heads. I can have the heads for next to nothing. Are they worth the effort of taking then off. I know that the 400 6X heads come with 2.11I and 1.66E valves and slightly larger chambers. How about the 350 heads? Do they flow as well as the 400 6X heads. Any info and suggestions would be appreciated. Thanks.

Responses

67 GOAT Bio 11/15/99 11:24

the 3560 6X heads are usually the small chambered version of the 6xs. They should have a "4" embossed on the machine pad above and to the left of the passenger side head. It depends on how much your time is worth. I have seen 6X-4 heads for sale as little as $50/pr and as high as $150/pr. This is bare, virgin heads. I think it is up to you. If you have a 400-455 and are thinking of increasing those ets, then yes grab em. I wouldnt plan on turning a large profit, as they are failry plentiful, around here anyways. Some have said that they can be made to flow as good as the RAIV heads. Cant say from experience one way or the other. All I can say is that when worked properly (ie ported, exhaust crossover filled, etc)they are a killer set of heads on a 455 because they up the CR into the 9s.

- JK 11/15/99 12:17

67 Goat – Thanks for the info. They are available for $25 the pair, complete, so I guess I'll grab them. JK

- 69GTO's 11/15/99 19:05

Don't pass them up at that price, if they are not beat. Everyone should have a set of 6X's sitting on their garage floor just in case needed. I do. And 400-4X's. I have paid as low as $35 bucks for a set of 6X-4's and sold then for as much as a $100 in good cond. Someone is always looking a set.

brad Bio 11/20/99 16:53

Get the carb off that motor too! If its the original its a 800cfm unit

Topic: 13089

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- Finding 6x code - jeff jknecht@colorhouse.com 11/30/99 13:34

I have searched the archives on two different occasions regarding the numbers, 4 and 8 that are supposed to be stamped on the rear exhaust port,but need advice. I looked very thoroughly last night and was unable to find either of those numbers stamped on my heads. I even popped the valve cover off to look, but no success. Can anybody tell me whether a 78 Trans Am 400, 4 speed car has the 98 or 92cc chambers?

Responses

Bob F Bio 11/30/99 13:51

Website: http://www.angelfire.com/wa/angryclown/CanAmW72.html

This link may help, but the info there is limited. I think that the 78 T/A with 4 speed came in both standard and W72, so you could have either 6X-8 or 6X-4 heads on your car.

David Holmberg Bio 11/30/99 14:58

You have to look up to see it. It is best to look on the drivers side, below the valve cover bolt there is a raised section with the end milled flat the # is stamped on that. If you use a small mirror you can see it much easier. My guess is with a 4-speed car they should be 4's.

- JK 11/30/99 15:15

Jeff – Bob maybe right on the 78 TA, but on the 77 TA you could only get the 4 spd with the HiPo engine. That meant 6X–4 heads (smaller chamber), as I just found out. The number is stamped on sort of a flat pad on the head above one of the spark plug holes. The number is not very visible, but should be there. You may have to clean the head, or at last the pad quite thoroughly to read it. The number is not raised like the head or block ID number.

edpete Bio 11/30/99 18:37

I thought the "Y6" engine was a HiPo 6.6 litre on the 77s and those are automatic blocks.I reference the Can am for example with the Y6 and auto,same for T/As isn't it?...Maybe Bob can check his engine as he has a Y6 engine...

Mr. W72 Bio 11/30/99 18:41

Contrary to popular belief there were two different 6X head designs. The base 6.6 Litre motors had the large chambered 6X #8 head that produced between 98-101 cc's. The T/A 6.6 motor used the smaller chambered 6X #4 heads that produced between 89-91 cc's. These heads helped increase the compression ratio from 7.6:1 to 8:1. It has been rumored that the true compression ratio on a W72 motor is somewhere between 8.6:1 and 9:1. Both heads used 2.11 intake, 1 .66 exhaust valves, and 1.50 rocker arms. The main difference was in the size of the chamber scallop. The 6X #4 heads can be identified externally by the number 4 stamped on the bottom side of the flat machine pad located towards the top front of the driver side head. This pad is just below the rocker cover and between the front and center exhaust ports just above the brass temperature gauge fitting. By placing a small mirror under this pad you should be able to see the stamped number 4. In comparison the 6X #8 heads will have the number 8 stamped in place of a 4

- jeff jknecht@colorhouse.com 12/1/99 13:33

Thanks everyone for your help. I found it after scraping paint off with a razor blade. They are the #4 code heads.

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- 6x-4 heads on 400 - Old Dog Bio 12/10/99 22:26

What would my compreshion ratio be if I put 6x-4 heads on a stock 400 in my 71 GP. As of now it has 6x-8. But due to a bad head gasket ,I have to yank the left side. Should I go ahead and yank both sides and replace with 6x-4 or stay where I am . I dont plan on to much further in the engine build department, maybe a cam later next year.

Responses

- 69GTO's 12/10/99 23:13

Probably about 8.5 to 1 or alittle more. There are other factors beside the head vol to consider too. I don't know that you would see much of a noticable difference.

Old Dog Bio 12/11/99 8:19

Forgot to add 1 more ? What would be a better set of heads (assuming I could find them)with out having to refinance my house for a down payment

67 GOAT Bio 12/11/99 14:45

Dont the 6x-4 have 89cc chambers? If so, running 89cc chambers Im guessing around 8.9-9.1. There are many other factors. Overbore, deck height, gasket thickness, valve reliefs. If it is a stock bore 400 with, say 0.015 deck, 7cc valve reliefs, and a 0.041" gasket thickness my calcs come to 9.01:1. an 0.030" over bore gives 9.13, then zero deck the block gives 9.26. Or milling the heads will decrease chamber vol., but be sure to mill the intake also.

joe B Bio 12/11/99 19:13

Didn't pontiac rate this combo for the 79 T/a at only 8.4. jo.b.

georgew Bio 12/11/99 20:02

Old Dog, did you try looking around the junkyards for '67-70 400 heads? I've found quite a few in yards in Houston, and there should be plenty out there in Phoenix. The Indian Head Code database in the restoration section of this site lists the good casting numbers. You will get around 9.75-10.25 compression with those older heads, and they have the big 1.77 exhaust valves. 6X only have the 1.66 valves. By the time you upgrade the 6X to big valves and mill the block or heads to bump the compression, you can spend just as much money as if you bought better heads to begin with. Also, milling the heads/block can lead to valvetrain geometry problems. IMHO, 6X are good for a 455 but there are definitely better options on a 400.

LStathas Bio 12/12/99 21:24

Why would the 1.66 exh. valve hinder it's performance on the 400 and not the 455? What would be the ballpark maximum hp a guy can expect out of a 400 with 6X-4's. I know it's been covered before but could someone quickly explain why the E-heads use 1.66's and flow so well? Is it just the port design?

- Bill Boyle bboyle@boyleworks.com 12/13/99 3:49

Website: http://www.boyleworks.com/ta400/musclecar.html

The 6x-4 still needs a chamber size in the mid to high 80s to yield 9 to 1 on a .030 over 400. With these heads never assume you know the chamber size from what you read. Have the chamber's cc'd before any milling is considered.

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- 6x-8 heads on 74 400 - derric dollens@socket.net 12/24/99 19:35

I recently purchased a pair of 6x-8 heads and want to istall them on a 74 400 that is stock.What compression would I be looking at? I realize this would be in the 8's but I want something I can put 89 octane fuel in. This would be installed in a 69 Ventura. I also have a Summit cam I got in a swap unused it is a SUM-K2801 duration at .050 214 in-- 224--ex lift 442--in 465--ex lobe sep--112 What kind of performance would this get me with the 6x-8 heads. Is the cam too big? I will use 600 holley, dual exhaust with stock manifolds, automatic with stock converter, 2.76 gears. I am glad I found this page I was having trouble finding a Pontiac chat room. I will tell my Pontiac buddies for sure.

Responses

TempesT68 Bio 12/24/99 19:50

the 74' 400 will have dished pistons, and the 6x-8's will put your compression in the mid 7's, it will run more then fine on 87 octance, with the 2.76 gears, this thing will be quite sluggish, expect mid/high 16's in the 1/4 mile

- derric dollens dollens@socket.net 12/24/99 20:56

I thought pontiac rated 400's with these heads at 8to1 compression.

JB Bio 12/24/99 21:03

74 will have dished pistons........not flat-top pistons.More chamber volume=lower compression...........JB.

- Will willbaker@home.com 12/24/99 21:22

Huh? The only Pontiacs I've heard of with dished pistons from the factory were the 428s. Of course, I've never actually torn down a stock 400, but I've always heard that the 400s all used flat tops and the differences in CR were due to chamber volume changes. In any case, the 6x-8 heads have 98-101 cc chambers which would put the CR just below 8:1. It was the 6x-4s used on the W72 400s that had the smaller chambers.

tonto Bio 12/24/99 22:17

I've seen at least one stock smog era 400 that had a chamfer going around the top edge of the piston. Just an eyeball guestimation, but I'd say it's good for a 6-10 cc increase in chamber volume. Certainly not a "dish", but the effect on compression would be the same. If I was going to venture another guess, I would say the compression would be slightly below 8:1. Anyone know how many cc's these chamfers add to chamber volume?

Witchdoctor Bio 12/25/99 0:39

The `75-76 400s had the beveled pistons. The `74 should have flat tops with normal valve reliefs. The `73-74 400s were advertised as 8.2 to 8.4, with the same nominal 98 cc. chamber. WD.

Ivan Bio 12/25/99 18:11

Some 74-76 400s with the 6x were as low as 7.2-7.4

- Rick 12/26/99 13:59

The factory never rated them below 7.6:1.Also the 6X was first used in '76.The 4X was used in '73-'74 and the 5C was used in '75. They are all good heads on a 455,or shaved alot for a 400.

Ivan Bio 12/26/99 19:10

Motors Manuals had them listed as low as 7.2 in 76

- Rick 12/26/99 20:13

I don't usually believe what Chiltons or Motors have to say. According to the GM service manuals,the '76 400's are rated at 7.6:1.

Ivan Bio 12/26/99 20:28

You're right my mistake 7.6,brain fadeing again

- Cliff 12/26/99 21:03

If the head "cc" at 98 without milling or decking your final compression ratio will be about 7.7 to 1. With the cam you've chosen the engine should perform quite well. Pontiac engines in particular make excellent power on pump gas even with dismal compression ratios. Low compression engines also make less heat on pump gas so cruising on hot summer days woln't be much of a problem either. Before I switched to a 428, I ran a similiar engine in my Ventura (73) and it was quite potent for a daily driver.

- derric dollens dollens@socket.net 12/26/99 21:42

Thank you everyone for your input. I was afraid this cam would be too big. The Summit catalog says this cam should be used with a 500 rpm above stock torque converter. I didnt want the bog syndrome. I know that with pontiacs many times less is more. This is one of the reasons I like the old ones so well. I also have a set of 6x? heads that have been milled 60 thousandths on combustion side with a 4bbl manifold that has been milled 30 thousandths on the intake side. Would this make my compression too high for the 87 octane fuel? Or would I be better off using the stock 6x8s?

LStathas Bio 12/27/99 22:15

I think a good question here is: What would the maximum compression I could run and still run 87,89,and 93 fuel respectively. Granted there are other factors involved but let's come up with some ballpark figures for the guy to work with. here's my guess: 87=9.0 CR, 89=9.5 CR, 93=10.5CR. These are only my guesses,but I'd bet they're pretty close.

- Michael 12/27/99 23:15

Website: http://www.wauknet.com/douthitt/compresi.htm

Well, the new vette has an 11:1 cr that runs on pump premium, but....--Michael

Witchdoctor Bio 12/28/99 18:55

My guess is that you just put a decimal point between the two octane digits. 87 octane equals 8.7 etc. WD.

Will Bio 12/28/99 20:10

WD, that's generally considered a safe guess though there are several people who've shown you can run as high as 10:1 on 93 octane as long as very careful attention is paid to tuning. For someone who doesn't want any worries about burning holes in pistons or pounding rod bearings the octane divided by 10 method works fine.

Horst Bio 12/29/99 8:33

Witchdoctor is correct. Nothing unusual about the factory pistons. I just tore down my stock '74 400 and can confirm this. Assuming your heads are 98cc you should be right around 8 to 1 compression ratio. You could probably mill some off the heads to get to 8.5 or so. A previous post discussed the rule of thumb for the amount to mill off to get the cc's you need. The 600 cfm Holley seems a bit small since the factory Q-Jet was 750 cfm which is about right for a 400. Since you have a heavy car with highway gears and stock exhaust manifolds, I wouldn't go with a radical cam unless other performance changes are made.

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- 400 combo with 6x 8 - tony tony_a_scott@amat.com 1/1/00 18:08

Here is combo I will be building . Specs I have for pistons are the question. Cam Ram air 4 ,Pistons - 7016P part # stamped on top. This number was changed when TRW bought Sealed Power. The new part # is TRW L2279F30. Specs are CD = 1.715 , Combine Volume is 10cc Heads - Stock CC is 101. I think it was milled to 98cc. The machine shop wants to mill the head .030 more. He will also mill the intake side to keep the geometry with the intake manifold. It is very important for this combination to be in the range between 9.5:1 to 10.0:1 to work with cam. The heads are 98cc now - 10cc dome = 88cc. If my math is correct this will yield a compression of 9.0:1. Is my math correct ? Tony

Responses

Will Bio 1/1/00 20:14

Tony, I think we need more info. If I get what you wrote correct, you have pistons with a 10cc dome? How much are you overboring your block? Is the block being milled for a zero deck height? Do these pistons have any valve reliefs in them? Assuming a zero deck height, .030" overbore, zero valve reliefs, I get 9.56:1.

- Cliff 1/2/00 4:40

I didn't follow the piston volume either. Is that a domed piston? If its a flattop with 2 valve reliefs, the cc's of the reliefs is added to the total volume above the piston. You also need to factor in the head gasket compressed thickness. Once you add up all the volume available above the piston, you can compute the swept volume and determine the compression ratio. Generally speaking a 400 without milling and decking using 6x 98cc heads and flattop piston will be about around 8 to 1 or a little less. Without doing any math you'll have to loose about 20 to 25cc's somewhere (over the stock configuration) to get where you want to be. I'm just curious what this engine is being built for?

MikeB Bio 1/2/00 21:07

From the topic he says 6x8, aren't those heads 101cc or a little more. Left bare that would give him 7.6 to 1 right? Are you trying to stay all #'s matching, down to the correct part?

- tony 1/3/00 6:43

It is a 400 motor with a .030 over bore. Stock thikness head gasket. The pistons have a 10 cc dome. Hope this helps..

- Cliff 1/4/00 5:36

Tony, looks like you've got just about all the info to compute your "actual" compression ratio. The only thing left is bolt in the crank and a piston/rod assembly and see how far down in the hole they are (distance below the deck). Then measure the gasket thickness you will be using and add up all the numbers. Without decking or milling your current combination should be around 9 to 1 or a little less. You can make plenty of power on pump gas at 9 to 1. My 428 is 8.8 to 1 and I use 89 octane Amoco gas, It makes more power than my 3100lb car can handle.

Topic: 13782

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- 6X's everywhere! - Stevie Ray Bio 1/3/00 1:43

San Diego: I went to the J-yard (Ecology on Energy way) this weekend and saw at least 6 cars with 400's with 6x heads if any of you guys that live close to here feel like getting dirty and dragging heavy iron around. A complete engine will cost $275.00 out the gate, subtract $80.00 if you bring a "core" and you decline the warranty they charge you $45.00 dollars for and it's only good for 30 days. A set of heads is about $100.00 This is a pull it yourself yard but there are "locals"who hang around to pull parts for people who will yank one out for about $40.00 //Disclaimer: No I don't work for them or have any relation to them whatsoever, I just wanted you guys to know. Oh, if your a Cop or some type of peace Officer you get half off and pay no core!

Responses

Greg Minor Bio 1/3/00 22:14

Hey Tony come visit me and we will go shopping

- Cliff 1/4/00 5:44

Found a junk yard on a huge farm not far from here. Pittsbugh Pa. Got at least a dozen 350's and 400 Pontiacs with 6X heads. $20.00 each you pull em. Complete engines $120.00 (no warrentee) $40.00 extra for them to pull em. It sounds good but its tough to pull heads in a junkyard, they are nice enough to torch the exhaust pipes loose for ya.

cobrabill Bio 1/4/00 20:43

Just picked up a 74 455 sr coded motor complete for $150.00.I'm going to enjoy good boneyard days like this while i can.

Stevie Ray Bio 1/4/00 20:47

Get out there boys! Save this stuff, aint being made anymore, Oh, great score Bill!

pontiacjeff Bio 1/5/00 11:29

Only in wacko-commie-lib. California would a jy have to name itself Ecology Auto Parts, (probably to keep from being put out of business). The yards in Ga. should go by names like Oil Slick in the Clay Auto parts, Stack'em Five-High Auto Parts, or, in the case of my own "virgin" jy which is filled with 50's and 60's cars, I have nick-named it Cow Pattie Auto Parts, for obvious reasons.

Steve Chin Bio 1/5/00 13:23

Well, out here we have a chain called Pick Your Part (we call it Pick Your Butt), and another called Pick-N-Pull (aka Full of Bull). There are others, but most of the rest are mom-n-pop J-yards.

- Rodney warpath@hotmail.com 1/5/00 21:32

In MI there is NEVER any Pontiac stuff in the yards. They crush everything around here. If anyone in MI knows of any good yards I would appreciate the tip.

64GTO Bio 1/6/00 7:39

You guys out west seem to have alot of yards! Anyone know of anything in CT or close to CT that would have any Pontiac parts. I would also appreciate the tip. Thanks.

Topic: 14246

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- #4 6x heads - Roy Seals seals@internetwis.com 1/20/00 22:22

For peace of mind, 1976 6x #4 heads from a 350 will bolt right on to a 1976 400 that had 6x #8 heads with no problem. Am I right? The reason for the switch is I am going to have the 6x #4's milled to raise compression and they have a smaller chamber to start off with. Put my mind at ease.

Responses

- gregg 1/20/00 22:45

yes they will fit. I have a pair of 6x-8's on a 455 and 6x-4's on a 400. any head from 60 somthing up will interchange. Mill the -4's .060's and you have close to 9.3 CR on a 400.

Topic: 14321

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- 6x head umbrella seals? - Steve fortking@aiservices.com 1/24/00 14:35

Doing the build up on my 79 th-Anniv TA.... 400 4sp...do these heads need the umbrellas in addition to the o-ring seals? The master rebuild kit I ordered has what appears to be Chevy umbrellas. They're too small to fit over the guide boss. Apparently Summit(or anyone else) has this item. Will another make work, ie...olsmobile, ford? Are they recommended? Thanks for the help!

Responses

- PONTIAC DUDE 1/24/00 15:03

Take your heads to a machine shop & have them cut for the late model 86-92 cheby seals. These are the boot seal w/wire retainer on the intake & hard plastic on the exhaust for todays junk gas & higher exh temps. Later.

- PONTIAC DUDE 1/24/00 15:04

Oh, also use the o-rings too, in the second groove down from the top of the stem..

- Cliff 1/24/00 18:13

If your using new parts, valve guides and new valves and clearance is at a minimum then the "O" rings alone will work fine. They must however be installed correctly-put them on after the spring is compressed just before you install the keeps. If not they will be pushed down on the valve and do no good whatsoever. They must be used in conjuction with the factory oil shields over the springs. If the guides were not renewed and the valves are used then clearance will be somewhat more than minimum and the use of an additional seal would be a good idea. Some shops use a positive type seal in addition to the "O" rings on the intake and an umbrella type on the exhaust, others use positive types on both and skip the "O" rings altogether. There doesn't seem to be an single accepted method and lots of opinions on the subject. I use the "O" rings alone with new parts and oil consumption is minimal. I do not like the teflon style positive seals and have seen many a valve guide worn out quite rapidly from lack of lubrication. Others swear by them, again its a matter of personal preference.

Witchdoctor Bio 1/24/00 20:46

Cliff sees the situation about the way I do. The older Pontiac heads were machined for positive seals on the intake only. The guide top were machined to a fat 1/2" (.531" comes to mind). What I call positive seals come in the plain rubber units supplied with most gasket sets. The Seal Power item, which is the same, except for a small imbedded teflon ring, which I prefer. I do not like the full teflon units, because of the stem wear Cliff mentioned, but also that they stand up so high that retainer to seal clearance is more of a problem. The late Pontiac heads are not cut on either guide, and they use a membrane seal, which many call the umbrella, on the intakes only. On rebuilt virgin heads, with normal guide wear, I cut the tops of the guides for positive seals, leaving .090" of the spring locating seat. Then I hand knurl and broach the guides. Go ahead and laugh, but I have gotten much better service out of this procedure than K-line bronze liners, and without the seat screw ups that are usually a part of having the guides totally replaced. I use the positive seals on all guides, O-rings on all stems, and the oil hats over the springs. I don't have valves hanging in the guides. Oil consumption is nada, and the seat seal is solid well past 50K. miles. One more thing to watch. Aftermarket keepers are available for juggling installed spring height, BUT only the stock Pontiac keeper will alllow the O-ring to stay in the groove where it belongs. Been there, and screwed that up. WD.

- PONTIAC DUDE 1/25/00 10:54

Name one engine currently being built that uses just the old fashion o-ring for oil control. This is old school thinking. Remember unleaded gas with raised combustion temps. better ring seal for more intake draw, yada,yada. to much to get into. install the seals & forget future headaches. what will it hurt? No teflon seals as they are for short term usage. Under usage the valve moves sideways in the guide over a period of time & the teflon wears oblong. later,dude

- Cliff 1/26/00 16:04

I am proud to be old and use old technology when it works. Anything that I post stems from over 2 decades of hands on expirience. Trying, succeeding, failing, learning. I do not speak about things that I have not personally tried and have only read about our been told by someone else. I do not know it all and leave myself open for improvement.

Topic: 14326

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- 6X-8 Heads-Worth???? - Ron in La Bio 1/24/00 18:08

Guys, what is a fresh set, in plastic from the machine shop, of 6X-8 heads with RAIV valve springs, 1.77 exhaust valves cut in worth? I might be selling this set.

Responses

- Todd farland@cts.com http://www.pontiaconline.com/members/3

http://www.pontiaconline.com/members/31/24/00 18:10

About $50 more than what you've got in them. Maybe.

- Cliff 1/24/00 18:43

What size combustion chambers do these heads have and what other work was done to them, new guides? stainless valves? retainers? 7/16" studs? milled?

Ron in La Bio 1/24/00 20:05

The heads have the 3/8 screw studs, new guides and seals, retainers, and I am not sure on the exhaust valves. I will have to check. I bought like this and haven't used yet.

Ron in La Bio 1/25/00 18:32

Ok, the heads have new bronze guides, RAIV exhaust valves and springs,new keepers, chambers cut for the 1.77 valves with new seats, 3 angle valve job. The heads were milled 10 thou. I did not put the 7/16th studs on them.

BVR421 Bio 1/25/00 20:09

ra4 ex? wont that be longer than the intake valves?

padgett Bio 1/25/00 20:22

Bet the exhaust seats are no longer hardened.

Ron in La Bio 1/25/00 21:09

No, I think the guy was wrong telling me about the valves. I am sure he just meant RAIV Springs.

Witchdoctor Bio 1/25/00 21:13

If you have RA-IV springs on a standard stack height, you got a problem. WD.

Ron in La Bio 1/25/00 21:19

Thanks for the info guys. I think that I need to have the heads checked out by someone else to find out exactly what I have. Things are adding up.

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Topic: 14363

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- swaping 13 heads for 6X-4 - gregg 1/25/00 21:09

I just reread my old post "RA 3/TA 6.6 compare" and came up with a good question. Has anyone took a RA 3 motor and swaped a set of 6X4's in place of the the 12's or 13's? if everything else is the same what would be the diff in performance

Responses

Steve Chin Bio 1/25/00 22:28

Not a lot of difference in performance if all else were left the same. The performance would probably go down a little on a 400 due to the loss of some compression and the 1.66" exhaust valves.

- jeff 1/25/00 23:35

amazingly,I have done that head swap!On a 70 GTO, automatic,# 13s-all stock,except 3-tube headers.Had a 3.55 rear.It was a little tired,and would "ping"on regular gas,at the time,HPP magazine was pushing the 6Xs-I swapped them,cleaned the carbon off the piston tops,the 6Xs were just freshened up-not all new.The car was noticeably less powerful,but the ping was gone.

Jerry Coffee Bio 1/26/00 7:53

Gregg....Just do it!!!! You will like it!!! High CR plus RA IV cam = horsepower! Just as the guys that own a 426 Max Wedge Dodge! Those engines had 13:1 CR.

- Cliff 1/27/00 6:10

I recomend taking the extra time and expense to open up the 6X's for the larger exhaust valves. Many years ago I replaced the #96 heads on my 428 with a fully prepared set of small chambered 6X's. The performance increase was substantial.

MikeB Bio 1/27/00 9:39

Cliff, I wouldn't think that a set of prepped 6X-4's would be better than a average set of 96's. Were they 68' or 71' 96's? That would make a big difference.

- Cliff 1/27/00 11:35

They were the #96 1971 GTO 400 heads. I set them up with all new parts including guides. Nearly as I can remember they were around 94cc when finished. I replaced them with a set of 6X heads off of a 77 350. 88cc when finished, larger exhaust valves, slight porting on short side radius, smog bumps removed. I also made a couple of stones to duplicate the factory bowls and performed a nice valve job both intake and exhaust. The compression increase may account for some of the power increase.

- Lee http://www.pontiaconline.com/members/455

http://www.pontiaconline.com/members/4551/28/00 12:01

Gregg, do you mean take OFF the 13's and replace them with 6x's? My cousin's T/A with an HC-02 cam ran 14.3's with 6X 8's, swapped on a set of 13's and ran 13.5's. But with a small cam I doubt there would be much difference.

- PoundHound 1/29/00 16:48

I am about to swap a set of #13s onto my 74 Ventura. When the 400 was put in the car the only heads the previous owner had was the #46 heads off the original 350. It has a bigger cam and headers and I am hoping the #13s help it breath a little better. I would think the added Comp. And bigger valves would help it. Just have to pay a little more and run 92 octane to stop the pinging...

- Cliff 1/30/00 8:44

PoundHound, the increase in airflow will be about 10 percent, in addition you will raise the compression which will give you a noticable increase in both torque and horsepower. Don't throw out the #46 heads. They are a good candidate for later upgrades. They can be easily upgraded to the larger valves with todays modern seat grinding equiptment. By working with the "virgin" metal the valves will be at the correct height for good airflow and correct valvetrain geometry. As far as airflow goes a set of modified #46 heads will flow as well as any other "D" port head.

Topic: 14404

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- 6x heads - nic young baits72chevy@yahoo.com 1/27/00 9:49

What is the best heads to have I have heard that the 6xs are. I have them on my 400. I also have a pair of 62,4x, and 16. What would be the best head to put on. THe 400 is mostly stock with a RA IV cam in it. I have a sp2p intake with a holley 650 running 66 in the primarys and 76 in the secondaries, I have a turbo 400 with a shift kit with stock converter. What head swould be the best to put on. One more thing, I was wondering if 4xs came with screw in studs. Thanks

Responses

- 1/27/00 9:59

With a RAIV cam you need high compression. That makes the 62s or 16s your best choice because they have small chambers, around 72-75 cc.

geebjen Bio 1/27/00 10:49

4X heads came in mutiple varieties, with both screw-in and press-in studs, as well as chambers from high 90's cc to 115 cc.

- Cliff 1/27/00 11:53

The 6X heads came with several chamber sizes. 98cc being the most common. 350's and a few 400 will have 6x's that cc around 92cc. The cam your using has considerable duration and overlap yet with it's 114CL it is a streetable cam. Although better suited to the smaller chambered heads with the correct parts you could use the 6X's. In addition the intake/carb setup you've chosen is quite restrictive and will limit available horsepower.

Will Bio 1/27/00 18:44

The best heads are the ones that are right for your combination and goals. 6X heads can work great in the right street application, but are not the best choice for a racing engine that needs high compression ratios. With your RAIV cam, I'd think the 62s would be a better choice.

- nicholas young baits72chevy@yahoo.com 2/1/00 9:25

Cliff I believe you said my carb and intake sucks why and what would work better I have money to spend and have lots of pontiac parts laying around. I have an edelbrock torcker from way back would that be a good intake. Thanks for all the info.

- Cliff 2/1/00 11:08

It's hard to beat the stock intakes, they will work as well or better than most of the aftermarket aluminum ones for street or street/strip cars. The performer RPM is the only dual plane that works any better. For big horsepower Pontiacs I like the open plenums like the torquer, warrior or street domimator.

- Rick Thornton thorntonr@wapa.gov 2/1/00 12:52

I talk to the tech people at edlebrock some time back. They told me that the sp2p was designed for the low comp. retarded cam engines of the late 70's. He also said he could not recomend putting it on anything. The power band ws designed for off idle only with no midrange breathing.

Steve Chin Bio 2/1/00 13:02

Rick, that's an understatement. An SP2P on a 326 will severely restrict its midrange breathing capabilities.//Nicholas, I've made no secret of my loathing for the original Edelbrock Torker because it's kind of the opposite of the SP2P (no bottom end, barely any midrange, and reasonable top end that falls off rather abruptly). They can make good intakes if they're massaged by someone who knows what they're doing, but the Holley Street Dominator is a MUCH better intake that hardly loses any top end to the Torker and has LOTS more bottom-end. As Cliff said, it's hard to beat the stock 4-barrel intake (and they are CHEEP at the J-yards!), even the restricted secondary '75-up intake is better than that SP2P.

- Ron Wagner rcwagner@bellsouth.net 2/1/00 20:22

Are the factory EGR 73-74 manifolds the same as the earlier ones in respect to flow, RPM range, runner size, ect. How would the 75 and up ones flow if the secondaries were opened up and the EGR receses filled. Thanks RW

- Cliff 2/2/00 11:34

They are pretty much the same casting with the exeption of the EGR bulge just under the one secondary opening.

Steve Chin Bio 2/2/00 14:56

The '73-'74 manifolds are essentially the same as the '68-'72 intake as Cliff said (except they have EGR, but the EGR port is on the floor of the manifold's plenae). The '75-up intakes appear to be more constricted at the port openings, but perhaps my memory fails in that area.

brianb Bio 2/2/00 20:13

Stay away from late 70's intakes. Starting in '77 (and maybe earlier) the secondary opening are smaller than those on the earlier intakes, thus resticting flow. The 6X head is a great head for a street (ie - pump gas) engine. Try to find the smaller chambered version that has a "4" stamped on the boss on the side of the head (above the spark plug holes). To bring your compression up to 9.5:1 though, you may need to shave them. If memory serves correctly, on a .030" overbore 400, you'll need a chamber size between 80-86 cc's to achieve 9.0:1-9.5:1 CR. You can run a R.A. IV cam in a 400 with this kind of compression, but I can think of a few newer cam grinds that aren't quite as "radical" that will give you the same power on the street as teh R.A. IV and provide better overall driveability. I'd shoot for something in the area of 220-225 degrees duration (at .050" lobe lift) on the intake side and 225-230 on the exhaust, on a 110-CL. This will give you good power and streetability.

- kevdog 2/2/00 20:29

I understand that the later intakes can be opened up to match eary intakes.

- JK 2/3/00 14:43

Steve – I've heard comments similar to yours about the Torker before. I have a new one that I purchased in 77. It's just collecting dust. My son was thinking of using it for his LeMans, which will receive a relatively mild 455 some time within the next year or so. What kind of massaging are we talking about here? Or should he just scrap the idea and go with his 71 intake or a Performer RPM? Also, when you are talking top end that falls off abruptly, what kind of RPM range do you mean? Thanks.

Steve Chin Bio 2/3/00 15:48

JK, some port filling and re-shaping, some plenum re-shaping. It's tedious work, but when you're done with it, you can be proud that you've done it yourself. Depending on how your son's engine's cammed, the '71 intake would probably be sufficient, but the Performer RPM< is a hard to beat piece. The power on the Torker seemed to fall off abruptly at what would be nose-bleed RPM for a 455 (well over 6500), so I wouldn't be too concerned with that...

Topic: 14976

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- 6X heads - Poncho72 Bio 2/19/00 21:59

I have a set of 6X heads that are in good shape. I met a guy the other day that wants me to sell them to him but I don't know how much they are worth. He said some thing about trading a disk break posi rear end for them.. The rear is out of a late 70's T/A and it has 3:42 gears. will these gears fit in a 72 LeMans rear? how much is the disk rear worth? sorry for rambling P72

Responses

tolerico Bio 2/19/00 22:39

Wont fit your lemans, but I would trade for it anyway and sell it...then buy E-heads....oh no here we go again... ;-)

- Cliff 2/20/00 6:08

The 6X heads have little or no value for restoration purposes. They are still plentiful enough that they do not bring big money at swap meets or in the trading posts either. Typically, they can be had from $20.00 each to about $50.00. They are however, excellent heads to "modify" and use on the larger engines. I buy and use them almost exclusively these days, especially the ones from 350's with the smaller chambers.

Poncho72 Bio 2/20/00 7:45

So the gears will not fit what ablout the posi unit? what size would the disk break rear be?

sugardog Bio 2/20/00 9:58

Poncho, your two cars probably both have an 8.5" corporate rear. If they do, the gears masy interchange. What is the ratio in the Lemans?

Poncho72 Bio 2/20/00 11:57

high like 3.08 or there close

m2pmd70 Bio 2/20/00 23:11

We pulled the cover off the rear in his '72 today... it is indeed peg-leg, the ring gear was marked 39-14... my calculator says 2.79, so I guess 2.73s? The late '70s WS-6s & stuff w/ disc brake rears use corp. 10 bolts like the '72 LeMans, right? So we could just pull the 3.42 posi carrier out & jam it in his '72 right? I'm not nearly an expert on this stuff.... if you swap the carrier do you have to mess w/ the intricate lash settings & crap?

- Cliff 2/21/00 6:11

Both rears should be late 8.5 ten bolts, but I would measure the ring gear diameters to be sure. The break for carriers is 2.73. Any carrier below 2.73 will require a spacer when using 2.73 and up ratios. Yes you have to set up the carrier. The easiest method is to use a dial indicator and measure the backlash on the rear your setting up. Switch out the carriers and use the original shims from the rear your setting up. This will duplicate preload and hopefully backlash. If the backlash is the same you are done. If it deviates from the original measurement then you will have to "move" the carrier by using different thickness shims. The only catch is that the total thickness of both shims is the same as the originals. To make this relatively easy you can buy "adjustable" shim packs from any co. who sells drivetrain parts.

m2pmd70 Bio 2/21/00 22:54

The carrier is the chunk of metal w/ the gears & posi stuff in it, right? If we pull the carrier out of the 3.42 rearend can we put it in place of the 3.08 peg-leg carrier w/o messing w/ the complicated stuff? Or would that work only if they use the same (pinion?) gear? From what I understand the pinion gear is what gets shimmed, right? So to my (obviously ignorant) thinking if the ring gear is the same diameter & they use the toothed pinion gear; then the carrier would be a bolt-in. Please correct me if I'm wrong, rearends (heh heh) are one of the many things I'd like to know a bit about.

- Cliff 2/22/00 4:54

The gearsets have to stay together, you can't mix them up they are "matched" sets. Being different ratios they will not "mesh" correctly anyhow.

m2pmd70 Bio 2/22/00 9:23

So we should just pull the rear & take both to our buddy the rearend genius? We're both capable of turning wrenches, but we're not very brave in our undertakings ;)

Poncho72 Bio 2/22/00 18:53

so what kind of money are we talking? what is a disk break rear worth(ball park. I'm going to look at it in the morning what sould i look for?

Poncho72 Bio 2/24/00 0:16

.

padgett Bio 2/25/00 17:56

IMNSHO uless you are racing, a disk brake rear is just a pain in the *rs*. Reason ? The parking brakes are a real bear to keep working (easy with a drum). Now I know that is not a PC answer but you asked. Now the 3.42 posi carrier, that is another story but if you can't use the housing, $75 tops - you will pay another $100 to get it set up properly in another case (assuming the Posi is good).

Poncho72 Bio 2/26/00 18:56

A friend at the local Pontiac dealer is going to build the rear. All I have to do is buy parts.. what is the deepest gears I could cram in this carrier?

Steve Chin Bio 2/28/00 15:16

Padgett, I find just the opposite is true. I have always thought that the drum brake is an over-complicated piece of gobbledegook and that disc brakes were just plain better. The parking brakes on my cars (and Blazer) show no tempermentality (is that a word?) and function fine. The only time I ever had a parking brake-related problem was when I had a bad ratchet in a piston.

Topic: 15425

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- 6x heads re-visited - joe joe Bio 3/8/00 2:22

What parts do I need to get higher lift rates using this head?I would like a safe margin of .500-.550 lift. springs,valves and so on. thanks jo jo

Responses

- Cliff 3/8/00 5:22

Several companies offer spring that will allow lifts to about .520" with the stock valves and installed height. You can use longer valves and springs that will go a lot higher, or you can machine down the spring seats in the heads. Using longer valves usually requires shorter pushrods unless the block and heads have been milled/decked accordingly. Reguardless what springs you choose set them at the recomended installed height. I always clamp them in a vise and check the coil bind spec. add .080", then subtract that number from the installed height. This number is the maximum recomended lift you can run with the springs.

Jerry Coffee Bio 3/8/00 7:51

See entry #15422. Comp Cams #995-16 valve springs are good up to .650" lift and set up at 114# at 1.700".Coil bind is 1.09" which safely provides up to .650" valve lift. In order to use those valve springs, the spring seats must be machined at least .114" or 5.202" long valves and longer pushrods must be used. It is easier and cheaper to machine the seats. However, if you are going to replace the valves anyway, get the longer valves and longer pushrods. I use Comp Cams equipment because I don't want to browse through a bunch of catalogs and their equipment is very good quality. I know all their parts by memory.

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