Pontiac Overheating Questions And Answers>
Pontiac Overheating Questions And Answers

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Topic: 7592

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- Overheating on highway - Nick 4/3/99 17:09

Here I was asking a question about fans in another post - little did I know I would be back so soon. Took the T/A out a road trip (about 400 miles) this weekend. After about an hour and a half at 70 mph, the temp gauge started climbing fairly quickly. Ran the heater, which helped a bit, until I could get to a gas station. By the time I made it to the gas station, the engine was overheating. I noticed that the slower I drive the cooler it ran so we finished the trip at about 45- 50 mph. Can you help? My guess is a clogged radiator, as everything else was replaced fairly recently, but the radiator is the original one, cleaned out many years ago. Another factor is that this car sometimes sits for extended periods of time (about 3-4 weeks) without being driven, so would that contribute to the formation of deposits? This is the first time I've had the car out for such a long drive in several years - usually I just drive it around town. Oh for info - 79 T/A, 160d thermo, stock clutch fan, A/C, Olds 403/350 trans. Thanks for your help.

Responses

joe s Bio 4/3/99 18:34

Check toe lower radiator hose - it might be collapsing. Is there a spring in it? Joe

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

..\members/html/4.html4/3/99 19:03

Your fan clutch is bad. First time this ever happened to me, it about drove me nuts. Car would only overheat at freeway speeds, fine around town. Clutch fan was basically new (as was EVERYTHING under the hood). Replaced "new" clutch fan with flex fan from one of my other cars, no more overheating problems.

- Nick 4/3/99 20:20

Yes, the lower radiator hose has a spring, so I think it's OK. I will replace the fan clutch - easy enough to do and see what happens. Since nobody said anything about the radiator being clogged, I will try the fan clutch before pulling the radiator. Thanks.

Tony deFoster Bio 4/3/99 20:23

get rid of the 160 degree thermostat and put in a 190. Had the same problem with my Street Rod. The water was going through the radiator too fast, at highway speed, to be fully cooled.

Scott B Bio 4/4/99 5:43

Does your T/A still have the air dam below the front bumper? My 78 T/A did the same thing because I wiped my air dam out on a parking curb. Didn't have enough $ to buy a new one so I used a peice that was used on standard Firebirds that mounts below the rad core support. This part forces air to go through the radiator at highway speeds, with out it or the air dam the air will not flow through the rad as it should at high way speeds. It's an aerodynamic issue with second gen F-body's.

Roar Bio 4/4/99 5:56

Hm is it necesary to have a fan when you ride on the highway. Shouldnt the air forced in by the speed be enough. I think Scott is on to something, if not thats the trouble I would flush the radiator even if it isnt that it will never hurt to do it. It can be so many other stuff to. BTW sure it was enough water on the cooling system. Could easily fool one.

- Nick 4/4/99 12:16

Scott - car is 100 0ntact - lower air dam is in place. This may be overkill, but now I'm thinking to change the fan clutch, thermostat, and go ahead and get the radiator cleaned out. I seem to have a fair amount of brownish discoloration in the coolant, compared to the small amount of miles the car is driven, so I really believe that besides the other items, the radiator may have more gunk inside than I thought. Thanks again.

Stevie Ray Bio 4/4/99 12:37

If your radiator isn't a 4 row, upgrade it. The spring in the lower hose sounds like a good place to start, also if your fluid is brown it definately needs to be flushed and then add a 75 percent, 25 percent antifreeze/water mix. Keep us posted, Good luck!

- DMR 4/4/99 13:12

I would at least have the radiator pressure cleaned, shops have a tool that puts air pressurized water through the rad to do a moderate clean, might not need a full take apart cleaning. I used to use Robertshaw high performance thermostat, but now they are marketed by Mr. Gasket, one of the few parts that are good and reasonably priced. I always use the air conditioner fans and clutches, as they have thermostats on them to control the slip, and the non a/c clutches don't, they work with a set drag. Make sure the pressure cap is in good shape, too.

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

..\members/html/4.html4/4/99 13:14

Yes, I know that it doesn't make sense that a bad clutch fan would cause a car to overheat on the freeway, but it can. (That's why it drove me nuts, it didn't make sense and I had a hard time beleiving it). After you check all the other stuff, if it still overheats at freeway speeds, try the fan clutch. I have seen this on several occaisons, so it's not just a flukey one time kinda thing.

- DMR 4/4/99 13:48

Todd, makes perfect sense to me, had my S10 lock the fan clutch up and stick the thermostat open all at the same time, 120 degrees is all it would go. Losing the viscous drive is not unusual, I think you made a great call with it. Sounds like this is exactly it. Has happened to me just that way, too. The fan cannot fully freewheel and cool, even at high vehicle speeds. Airflow from the front of the car will not cool the engine fully, and needs a little fan help. Nascar allows flat blade fans for 4 lap qualifying only, for drag reduction, but this is only 4 laps. Roar, it stays cold at the arctic circle, who needs a fan there? (hahahaha).

TempesT68 Bio 4/4/99 17:38

another thing that is very commonly overlooked is see if the radiator cap is holding all the pressure it is soppost to be, id just pick one up for a few bucks, you may be suprised

- Nick 4/4/99 20:45

Thanks very much for all the info. I'm taking the radiator out tomorrow for pressure testing. As I write this though, I think that I had better check that lower radiator hose. I earlier said that it had a spring inside, but now I'm not sure. What makes me wonder is that after the inital time it took to get the temp up, if you drove at 45 -55 mph, the temp was running hotter than usual, but stabilized. If you gassed it up to 75 or so, the temp would almost immediately start increasing - faster (it seems) than a restricted radiator would allow. The hose itself can be squeezed with just a couple of fingers on it, doesn't feel that there's anything inside. I will pull it and let you know. Thanks again everyone - appreciate the help.

Rhac Bio 4/4/99 22:35

Could be the tranny, sipping clutches. Had this happen, all OK otherwise and heat up on the hwy. Do not see how you could be unable to dissapate heat on the Istate and be OK at stop and go unless you were making more heat at speed. Think about what is different and then go from there.

Roar Bio 4/5/99 11:34

Well I forgot that I live in the arctic circle and arent rouble with the heat like you guys. :-( LOL

- DMR 4/5/99 11:37

Roar: BBBrrrrrrrrrrrrruh, COLD.....

Steve Chin Bio 4/5/99 17:12

Yeah, and they say that those cheese-heads have it cold!

- Wally lindawi@seacove.net 4/5/99 20:43

Nick I'm with Rhac on this I had the same thing happen I changed the fan clutch got a new radiator and it would still overheat on the highway at speed. Turned out the pump in the transmission was failing and the fluid as it was passing through the radiator was transmiting the excess heat to the engine coolent.

- Nick 4/6/99 7:28

Problem solved - I think. I ran the car yesterday and specifically checked the lower radiator hose. I had somebody rev the engine while I looked at the hose, and as soon as the engine revved, the hose sucked in. I let the car cool a bit, then pulled the hose and guess what - no spring inside. I could have sworn that there was one in there! Anyway, I went down to the auto parts, but when I checked the replacement hose, it also did not have a spring. I went to a local NAPA dealer and the one I got from them did have a spring ... go figure. Installed the hose, flushed out the system, fresh coolant, etc., then checked again - hose doesn't budge when you rev it. Drove the car on the highway with no problems, but will drive it longer this weekend to see what happens. About the transmission - my next project was to pull the trans and get the clutches replaced - several years ago the pump, and torque convertor were replaced, along with seals, but I was told that the clutches were pretty worn. The trans had also had a B&M shift kit installed at about 15,000 miles. Anyway, it worked fine after the work, but lately, it has begun to slip on hard accelerration, especially the 1-2 shift, plus I see more than the usual amount of clutch material in the pan when changing the fluid. I agree when you say that I may now be transmitting heat from transmission slippage at freeway speeds. There is a definite improvement (lower temp) with the hose replacement, though. Thanks again to everybody for the input - I have learned a lot from all the info, especially about thinking through what's happening and to always start with the basics.

- DMR 4/6/99 10:47

Nick, glad you got the car fixed. Sometimes the spring will be eaten away by electolysis and bits of it will go through the cooling system, so there could have been a spring when you first put it on. Now, go enjoy that Pontiac.

Topic: 8888

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- Overheating: flow/cavitation - AlienPoncho dlaray@earthlink.net 5/31/99 1:02

Seems Gordon Jennings is expousing that a fast flow of coolant is not the cause of poor cooling. Instead he says it is cavitation, causing slower flow. This is based on faster flowing coolant having a thinner boundary layer, which promotes heat exchange. This is contrary to what I've always believed, that a fast flow may prevent exchange where a radiator is the primary exchanger. Any thoughts?

Responses

- 5/31/99 1:39

Water running too fast doesn't allow heat transfer due to no time to transfer. Case in point, Ford Flathead or any engine without a thermostat or restrictor equals overheating. Flatheads were refered to as "Boilers".

- 5/31/99 1:42

BTW, Jennings has been around since dirt and hasn't figured much out right in all this time. He also thinks we should all run the hottest sparkplug we can find, richen mixtures and retard timings, too. Wrong, Gordon, still wrong.

Steve Chin Bio 6/1/99 17:02

I think that there is a practical limit to the speed at which coolant should flow. I have not arrived at a surface speed that is proper, but I have also not reached the practical limit where I start increasing temperatures. I also believe that there are a number of problems affecting the speed at which coolant best transfers heat. Cavitation could affect the transfer rate, but only as it relates to the water pump (since the true definition of cavitiation only has to do with loss of efficiency in the pump due to the fluid medium "stalling" over the pump vanes). Since the increase in orifice size is what we're talking about here, I sincerely doubt that a water pump is cavitating (less resistance to fluid flow in a pump = less likelihood of cavitation in the fluid pump). So, the only conclusion that can be reached from that is a loss of efficiency in the boundary layer between the radiator and the coolant medium (if all else remains equal). I like to increase dwell time in the heat exchanger if at all possible without affecting coolant flow through the engine because it takes less time to inject the heat into the cooling medium than it does to take it out, simply because of a much greater potential difference in thermal energy within the engine than within the radiator. The only way to accomplish this is by increasing the internal volume of the heat exchanger and its tanks. Notice that I did not say that I was trying to increase flow rate in the block/heads, but just trying to increase dwell time in the outbound heat exchanger (radiator). Anyhow, it's worked for me.

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Topic: 8975

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- Overheating AGAIN - steven 6/3/99 20:15

my 400 firebird has run hot on the interstate above 2700 rpm since I rebuilt the motor last year. I installed a new 4 core radiator, new waterpump with new bushing and plate, a new 7 blade fan with a stock fan clutch, a 160 degree thermostat and all shrouds. I have also played with the timing with no change. I saw searching the archives that a lower hose collapsing could be a problem so i checked and mine has a spring in it. However my top hose does not. Can the same collapsing happen in the top hose ? The engine runs at 180 around town but shoots up to 220 after 10 minutes of highway speeds. (60mph) i am totally stumped, everything is new yet i am still having problems!! thanks for any advice!!

Responses

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

..\members/html/4.html6/3/99 20:21

I gave up on clutch fans years ago, when after the same scenario, discovered that my brand new clutch fan had failed after only a couple of months and not many miles. Suspect that may be the problem here. Oh yeah, the upper hose doesn't get a internal spring. They don't collapse since they are the return hose. The lower hose is on the suction side of the water pump which is wide it needs the spring.

Huey Bio 6/3/99 20:54

This is a stretch, but you don't have a small pulley on the pump or crank that would cause the pump to turn to fast thus causing the coolant to flow though the radiator to fast? Like I said its a stretch but hey, I had to ask

Tony deFoster Bio 6/3/99 21:13

STEVEN - Get RID of the 160 degree thermostat and install a 180 or preferably a 190 degree unit.

Witchdoctor Bio 6/3/99 21:35

And, also check the radiator cap to see if it is actually holding the rated pressure. WD.

- Loyd Lucas llucas@ocsnet.net 6/3/99 23:22

Steven, What is your compression ratio? Also how much total advance are you running and are you using vacuum advance? Asking these things because if you are running the timing retarded because of high compression or not using a vacuum advance you can have exactly the symptoms you are describing. Good luck, and please let us know what fixes your problem so we can all learn.

- kevin turner kevsha@hpnc.com 6/3/99 23:40

I had the same problem in my new 400. A flex fan helped, 180 thermostat helped. Do you have an overflow bottle? If not this is mandatory to prevent air from entering the system. Also try redline water conditioner. It work great. I run 185 on the street and 200 if I really push it down the highway.

- DMR 6/4/99 0:18

Steven, a thermostat suggestion, use the Mr. Gasket ones, they are the best ones to use, and control flow and temperature. I use 180 degree stats, and no cooler. You might want to look into making sure the timing and curve(s), and jetting are correct, as lean mixtures and incorrect timing could contribute to steady speed overheating. Do check the other items listed on the above posts, there's a wealth of info there. Best luck.

Roar Bio 6/4/99 2:22

What year is the bird ? Any chances that the air isnt going trough the radiator at high speed. Some cars have som kind of guiding off the air into the radiator.

threedeuce Bio 6/4/99 16:54

I go with Roar's response. If its a later model Firebird, check to see if there's a flap/spoiler underneath the car in front of the car.. This flap scoops in air and creates a vacuum behind the radiator to increase airflow at highway speeds. Im sure this must be the problem. As a matter of fact, I had the same problem with a 87 camaro. Instaaled the flap and all problems solved! Good Luck!

- Rob 6/8/99 11:04

Hi Steven. What year is your Firebird? I have a '69 400 with a slightly different problem in that mine runs hot when idling. I have done everything you have done to fix it but it doesn't seem to get any better. In reply to the suggestion that you should install a higher thermmostat, I say no. The temperature at which the stat opens is irrelevant to final operating temperature if the car won't cool down (the stat only sets the minimum operating temperature). The pulley size is important to consider because it does effect flow rate. Another consideration is the size of the thermostat opening. some models are specially designed to have a higher or lower rate of flow, so look into this. I actually plan on removing my thermostat altogether in a effort to improve low end flow. There is a risk of running warmer at higher speeds with this technique, but that hasn't been a problem in the past for this vehicle. If you have any suggestions yourself, I would be pleased to hear from you. Good-luck.

padgett Bio 6/8/99 11:24

My Sunbird did the same thing until I replaced the fan clutch with a flex fan.Also are you running a vacuum advance, not having one will do the same thing and the advance needed increases (1) as rpm increases (2) as MAP decreases (vaccuum inreases).

geo Bio 6/8/99 13:27

Here's a couple of extra things I've run across. Had a wrist pin slip out against the wall. Ran 200 on highway. Do a compression check to find. Water Wetter DOESN'T work with gycol anti-freeze. Because gycol will hold the extra heat thats extracted (thats from the company that makes it). Run 30 percent, no more of gycol(summer). Lowered my temp 3-6 degrees. Plain water cools better, but has about 40 degree less boiling point. HD/RV type clutch fan ONLY. Then all the above as far as timing,carb etc.

- jktb 6/8/99 16:36

A 160 thermostat will open once then stay open and a higher temperature thermostat will open, then close after the cool water from the radiator passes over it, and continue this cycle until the radiator can't keep up. If the water doesn't get time to sit in the radiator it will start to overheat. Go get a good 190 thermostat and check all the above mentioned stuff.

- Meaty 6/8/99 21:31

I'm with jktb---go for the higher stat and increase your percentage of water. Water is still the best type of fluid to use in your system to dissipate heat.

- kevin kevsha@hpnc.com 6/9/99 0:02

heavily retarded timing will cause overheating as well as a lean mixture

Topic: 9385

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- OVERHEATING - Mike myckee@home.com 6/22/99 21:40

Hello guys. Here is the problem. My car overheats at idle, and doesn't seem to cool down even when at highway speeds. I have a 1980 firebird with a 1975 400 block and 1967 670 heads. I run 9.5 compression and I use 94 octane gas and I have a BHJ balancer. The intake is a performer rpm and I use a built up Rochester 750cfm. The cam has a lift of 475 on the intake and 483 on the exhaust with 228 and 237 duration respectively.The timing is set at 14 degrees initial and 36 total. I use a "high efficiancy" 3 row rad, a 160 Robertshaw thermostat and Warrior Racing products aluminum pulley set. The heater core has been bypassed and the heater outlet on the water pump has been connected directly with the fitting on the rear of the head. I have a fan shroud and run an 18" flexalite fan with two 2" spacers to put the fan as far into the shroud as possible and I am using dex cool coolant and water.I have tried messing with the timing with no success except when I really advance it beyond all reason, at that point it seemed to run a tad cooler. Then I thought it might have been that the balancer hadn't been degreed properly. I used a piston stop and found that it is bang on. I tried relacing the thermostat incase it was faulty and nothing. I made sure that the sleeves were in the timing cover and that the plate that is to be between the pump and housing is in place. The spring is in the lower rad hose and I also have an auxillary trans cooler hooked up as well. The radiator was brand new last year, and the engine is completely brand new. I picked it up from the machine shop 2 days ago. I'm at a complete loss as to why it is overheating. Any info would be greatly appreciated. Thank you very much.

Responses

bvr421 Bio 6/22/99 22:53

Mike, have you checked temp using a completely different temp gauge? Also, what temp are you calling too hot? I would not bypass the heater core as that is actually part of the factory cooling scheme. I prefer at least a 180 Robertshaw. I too hate cooling problems.

- Mike 6/22/99 23:26

The engine runs at about 220. Last year with pretty much the exact same engine ( the cam and balancer being the only changes) the car ran between 160 and 180 950f the time. Thats why I can't figure out the problem. The cam last year was pretty much the same.

- Meaty 6/23/99 6:43

Mike, all good Poncho's should run a tad on the hot side, about 190-210. I wouldn't worry too much. I would go to a higher thermostat though so the coolant stays in the radiator longer to cool down. I would also put the heater core back in line as well!

LeMan Bio 6/23/99 7:38

Break in the motor for a couple hundred miles and the temp should drop back to normal. If not then you have a problem, but I don't think that you can diagnose the overheating problem until you get her broke in.

geo Bio 6/23/99 8:25

Mike think about the 180 thermosat,don't do. I've tested with a 160, a 180, a 160 with 3-3/16" holes added and just a thermostat plate(center taken out). The hottest was with the 180. The rest were the same and runs the coolest. 195 in very hot conditions cruise at 70 mph at 34-3500rpms, 195/210 in town sitting/crawling in tracfic. In 70 degree type weather it runs 175/185 highway and 185/195 crawling around town. With the 180 thermostat I ran 5/10 degrees hotter in all situations. I have a big (5/16" tube) 3 row,30 percent gycol and HD/RV clutch w/7 blade fan. The fan is about 1/3rd of the way into the shroud. If your running 50 percent or more gycol anti-freeze, you will run hotter because the more gycol the more heat is retained. When I went from 50 percent to 30 percent I saw about a 5 degree drop in temp under all conditions. Just my experiences. I take it that dex cool is like water wetter? If so don't use gycol with it. The only problem with stats under 180 is it takes about 2/3 miles more to get to 180 degrees (std temp) at first and in fall/winter the 180 is what I use because the motor runs to cool.

- DMR 6/23/99 10:14

If the pulleys underdrive the water pump, change them. I have used 30 percent anti-freeze for years, have suggested to many, no-body listens, my stuff doesn't overheat. I use 180 degree Robertshaw stats in all my engines, and that is where they stay, even in the Central Valley of California when I lived there, in 119 degree days. I find engine water temps of 170 to 185 degrees is ideal for getting the jetting spot on. Cooler needs more fuel, hotter makes jetting impossible. Make sure you do the distributor curves as suggested by Jim Hand in his exellent article. Always use a vacuum advance for the street, make sure jetting is not too lean.

- Craig 6/23/99 12:02

The new issue of Smoke Signals arrived in the mail yesterday and it had a book review on keeping Pontiac running cool. I will bring it to work Thurs. and post the address and other info on it.

- Will wbaker@adobe.com ..\members/html/36.html

..\members/html/36.html6/23/99 12:10

Mike, one thing I noticed in your post that caught my eye is your putting the fan "as far into the shroud as possible." You actually want the rear edges of the fan blades to protrude from the shroud slightly. Ideally the blades should be half-in and half-out of the shroud. Putting the fan further into the shroud decreases it's efficiency. Don't know if this will solve your problem, but it can't hurt.

- Mike myckee 6/23/99 12:54

Thank you to everyone for your help. I'm going to try reducing the amount of coolant in the rad as well as removing one of the fan spacers. If I can get it to run at about 190 and not climb into the 220 range I'll be very happy. I won't try changing the thermostat just yet, but I definately will try.

Steve Chin Bio 6/23/99 15:44

Mike, why do you have the heater hose bypassing the heater core? Bypassing the core in this manner allows more hot water to recirculate into the water pump. If you don't want to run a heater, put a restriction orifice into the hose. The Warrior pulleys are supposed to be underdrive pulleys, so I would ditch them too (as DMR suggested). And, to reiterate Will Baker's suggestion, position the fan so that the blades are between half in and half out and one third in and two thirds out (as slightly less than half into the shroud is actually most effective). FYI, I run a Robertshaw 160 deg. thermostat and rarely (if ever) see more than 170 degrees of coolant temperature.

- Mike myckee@home.com 6/23/99 16:14

Steve, I bypassed the heater core because it is a bit of a pain in the butt to change. Ok, so when it comes to the meanial tasks I'm fairly lazy, but give me a motor sawp and I'm up to my elbows in grease...what can I say...I'm normal? :)

Steve Chin Bio 6/23/99 16:26

I see... Well, try putting a restriction in the heater hose and see if that helps. It won't help a lot, but every little thing in a situation like this gets you closer to where you want to be...

- Mike myckee@home.com 6/23/99 18:36

Well how do I go about putting a restriction in it? Shoud I have the heater core flow through a small piece of tubing or something?

Ken MacNicol Bio 6/23/99 19:58

I once had a problem while towing with air on in a 80 Firebird also. After trying thermstats,fan clutches,water restricters,had a friend who roundy round races PONTIACS told me to ditch clutch fan and install older style solid fan. It cured the problem by knocking temperature down about 15 degrees.

- Mike 6/25/99 15:31

Yeah, I had already heard that those clutch fans sometimes are crap so mine is just a regular flex type.

padgett Bio 6/25/99 18:25

Vacuum advance ?

- Mike 6/27/99 8:25

I'm not running a vacuum advance. Think that may contribute to the heat?

- Obeid 6/27/99 9:37

Mike, Vaccuum advance is sometimes essential to keep our cars running cool, especially idling. I found a huge difference when I switched my vaccuum source from ported to manifold. You don't mention the distributor type, if you have HEI or points, run it off a manifold vaccuum source and see what happens. Good call Padgett.

- DMR 6/27/99 10:25

Be careful with the vacuum advance, do visit the Jim Hand ignition set up articles. It is possible to have too much vacuum advance, so do what Jim says, and this should help with the heat. HEI distributors often have way too much vac advance for early engines, as the curves they have stock are for emissions. Good call, indeed, Padgett, I assumed with all that has been written in these posts and the archives, no-body didn't know about them and their benefits.

- Loyd Lucas llucas@ocsnet.net 6/27/99 13:47

If you don't have a vacuum advance hooked up you should. It is not unusual for an engine to run hotter at idle because of low coolant, and air flow, but it should cool down at moderate highway speeds. If it doesn't, one thing that can cause it to run hot at cruise even with good coolant and air flow is TOO LITTLE ADVANCE at cruise. This is what a vacuum advance is for. Good luck.

- Mike 6/29/99 11:07

Thanks guys, I'm off today so I'm going to hook up the advance. Should I connect it to the timed vacuum, or the manifold vacuum??

joe s Bio 6/29/99 11:24

if you are hot at idle, use manifold vac

- R 6/29/99 13:33

Mike, break in the engine and use a vacuum advance. Any changes in compression and cam will can definitely affect temp. If your cam is similar to the last one you ran but a little hotter, you may well run hotter temps. If you added the 670's on during this rebuild to make 9.5:1, that will heat things up a bit too. Check that fan spacing too. Good luck.

DONNY Bio 6/29/99 19:04

Heres a dumb one for you, I had a 68 Cougar Years ago...Thing had a over hot problem,,did it, all changed it all, checked it all....Well except for the radiator cap, it was leaking pressure. Make sure you check yours.... If they leak they will run you hot!!!! Could have died when I found that to be my problem after all the work..... Good Luck!

Topic: 10489

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- Overheating - Doug 8/9/99 12:53

Here is the basics. '68 stock 400 rebuild with RAIV cam. Engine has correct '68 front housing with brand new water pump and stainless seperator plates. It has a new 4 core aluminum radiator and a gutted thermostat. I have tried everything, but the car still overheats after about 10 minutes of in town driving/idling. I have checked all hoses/heater core etc. for blockage. Everythign flows fine. What could be causing my problem? Thanks in advance.

Responses

- David david84ss@hotmail.com 8/9/99 13:16

I had the same problem with my Monte Carlo. The engine would overheat even after I put on a new trans cooler/ radiator/ water pump. I eventually found it had to do with the distributor. I don't know all the technical reasons behind it, but the distributor curve was off and was causing the motor to overheat. Back when I was searching for a cure to my problem, I was also told that if the head gaskets are put on upside down, that will cause it to overheat as well. I Hope this helps you out?

Tony deFoster Bio 8/9/99 13:50

DOUG - Put in a 180 degree thermostat that is NOT "gutted", and that will cure the problem, all other things being in proper working condition.

Steve Chin Bio 8/9/99 13:54

Gutted thermostat? Perhaps that is the problem. Try installing a 180 degree Robertshaw (or other quality brand) thermostat and see if that helps. 4-core aluminum radiator? AFAIK, there is no such thing - the *rows* of tubes in the *core* of the aluminum radiators are flatter and longer than those in a traditional copper/brass radiator, and the cores of the radiators are usually made up of two rows of 3/4", 7/8", 1", or 1.125" tubes. The main reason being expense, and the other being heat transfer capability (fewer numbers of the larger tubes have actually been shown to transfer the heat better than larger numbers of smaller tubes, and because there are fewer tubes, they cost less to manufacture). Check to ensure that what you were sold is truly an aluminum radiator. Also check to ensure that the sleeves that connect the water pump divider to the block are intact and installed. Hmmm... To what temperature is the engine getting?

Jerry Coffee Bio 8/9/99 14:04

Yes, the gutted thermostat is a good idea. Why? You might ask. The coolant is not held in the radiator long enough to cool down. It is flowing too fast through the engine. Check your initial timing and advance it to 10-12 degrees BTDC. Retarded timing makes Pontiacs run hot. I know, I know, the book says 6 deg. BTDC but that is not with a RA IV cam. Besides, the book is for the old regular gas, not the high octane ethyl gas we have at the pump nowdays! (Joke)

Jerry Coffee Bio 8/9/99 14:05

Correction, NOT a good idea.

- sugardog @flash.net 8/9/99 14:08

heck, initial timing spec for RAIV motors was 15 deg. BTDC.

BA Bio 8/9/99 16:05

My 68 GTO had the same problem I fought on and off with for years. One thing that made a significant difference was the addition of a coolant recovery system. This has been covered fairly extensively - check the archives and try it. For the $20.00 or so that it costs, you will be pleasantly surprised, I know I was!

- Bracket Racer 8/9/99 17:47

All of the aforementioned are good things to look into and if that doesn't help your problem I might reccomend a product made by Redline called water wetter, available through Summit and Jeg's at about $7.00. This improves the heat transfer characteristics of H2O and prevents formation of steam vapor around water contact area on the cylinder bores within the block. I use it in my bracket racing 455 and it does wonders. Only drawback is that it works best with pure water (no anti-freeze) or with low antifreeze ratios. Also, is the fan within reasonable distance from the radiator and is it shrouded?

Huey Bio 8/9/99 20:38

Does the car overheat on the highway also or just in town driving. I agree with the others that you need a good thermostat, so start there. If the car runs cooler or at least at an acceptable temp while cruising on the highway, then check the clutch fan if it's not working properly then it will run hot while driving in town because not enough air is flowing thur the rad, check the fan clutch

Philbert Bio 8/9/99 22:47

I had a serious overheating problem with a 455 in a 65GTO. Tried water wetter, it helped a little. Tried a Griffen aluminum radiator, helped a little. Tried a new Clutch fan instead of dual electrics, helped a little. Put on a shrould and can now idle for 20plus minutes in near 100 degree heat and has not gone over 205 degrees. GET A SHROUD! best wishes,Phil

- 8/9/99 23:55

My 1986 3.0 powered Grand Am is having the same problem, I have replaced the thermostat x 3 (190 x2 & 160 x1), radiator, radiator cap (13 lb), heater core, hoses, coolant lines, water pump, compression is at 160-165 in all cyls., done a back flushing and it still goes up to 250 degrees with no heat at any time during warm up, which is about 20 minutes, I have done a pressure test as well, any one have any ideas?

BVR421 Bio 8/10/99 0:04

GAUGE ACCURATE?

BA Bio 8/10/99 0:32

Not to sound redundant, but I have been where you are and trying a coolant recovery system made a significant difference, really.

- 8/10/99 8:44

Yes, my gauge is accurate, I have also used a remote gauge and it goes to 250 as well.

LeMan Bio 8/10/99 8:52

Grand Am gut, for the temps to get that high sounds like a fan problem. Does the fan kick on when it starts to get hot? Perhaps there is a problem with the sensor that contros the fan.

- 8/10/99 11:40

I have grounded the relay so it runs with the ignition on, I am going to try another water pump today in case that one is defective.

BA Bio 8/10/99 11:47

No need to go to all that work - test the old one! It's simple - have someone rev the engine sharply while you watch the upper hose on a fully warmed engine. The hose should swell slightly. The water can only travel through the radiator so fast and then the radiator becomes an obstruction to flow. On a cool engine, remove the radiator cap and watch the flow of water inside as the engine is revved - you should see some movement.

BA Bio 8/10/99 11:52

I just thought of another way too, but it is messy. Pop off the lower hose at the radiator and reposition it downwards and submerge it into a bucket of water that is constantly being filled with a garden hose. Take out the thermostat. If you have a piece of universal flex radiator hose, connect it to the bottom of the radiator and direct it either into the bucket or downwards. Put on safety goggles if there is coolant in the system. Fire up the engine. You'll see whether your pump is pumping or not, I guarantee it.

Witchdoctor Bio 8/10/99 15:20

I've been searching for something not mentioned in the previous posts, as the situation sounds extreme. Were the block and heads fully cleaned? Is the spring present in the lower radiator hose? I'm vague on the `68 pump/timing cover set up. Does it use the same distribution tubes? Are the gaskets (o-rings) in good shape. Check the radiator tank for bubbles. An exhaust side leak can super heat the coolant in a hurry. I'll always remember my boss, who waited weeks for his special order T/A in 1978, only to find that it would not make the 30 mile trip to work on cool mornings without overheating. Repeated trips to the dealer solved nothing until they finally pulled the heads off to discover that not all of the transfer holes in the heads had been drilled. WD.

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

..\members/html/4.html8/10/99 15:39

WD, just for future reference, the 68 only uses the pump plates. The tubes with the rubber O-rings didn't show up until later. 73 for sure, but I'm fuzzy on the exact year that they first showed up.

Witchdoctor Bio 8/10/99 21:03

Right Todd, after I wrote that, I went back and looked. It appears that `68 was the last year for that style pump, although the engine uses the later harmonic balancer. I wonder if a swap to the later timing cover and pump would improve anything?? WD.

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

..\members/html/4.html8/10/99 23:09

I doubt that just swapping the later cover and pump would do much, if anything. I run a 68 timing cover and stock pump on my 421 and it runs pretty cool (considering what the engine combo is). Heck, I just run stock pumps and pretty much stock everything with the exception of fixed blade flex fans on all of mine (65, 67, the 68 on the 421 and the 73) and they all run cool.

- Doug 8/11/99 7:39

Problem Solved!!! Last night I installed the front cover/water pump/pulley off of a '69 and the car will not go above 195. I did notice that the pulley off of the '69 was about 1" smaller in diameter, causing the pump to spin faster. Thanks for all the input guys.

padgett Bio 8/11/99 9:39

The real answer is that all of the parts must match properly - the early pump must have the divider plate, the later ones must have the tubes to run properly. Am curious about something: my aunchient thermo studies say that a copper radiator is better for heat transfer than aluminum & the Vettes used Al because it was lighter and not much worse. As to the Grand Am, if the 250 is real, there is a serious internal problem there, probably something is blocking the flow completely - nothing out of the heater is an indication of this. None of our "late" cars (86, 2-90, 92), three of which are V-6s, have any overheating at all & cool down to the thermo setting as soon as the fan is on. Incidently in the course of thutty yar in Florida and Texas, have never used more than a factory HD radiator (three cores mostly but the Sunbird V-8 has a 2 core (no room for more, fan is Right There).

- Grand Am guy 8/11/99 10:52

This started like overnight, it was fine the day before in 100 degrees with the A/C on, then I went to start it the next morning and the temp gauge shot up, I figurd it was a stuck thermostat, I can't seem to find any blockages anywhere, but that doesn't mean there aren't any.

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- Re: post 10489 overheating - Grand Am owner 8/14/99 11:59

OK, it's a 1986 Grand Am with a 3.0 V6, I have replaced the radiator, cap, water pump (x2), thermostat (x4), all hoses incl. all short ones, heater core, cleaned all coolant lines, checked temp gauge, fan is wired to run with the ignition on, done a flushing, done a back flush, done 3 compression tests (all 6 - 160-165 still), done a pressure test (no visible leaks), and yet 20 minutes after starting the car the temp is at 270 degrees, is there anything I missed? Is the car possessed? Is there hope? BTW, my girlfriend's 1989 GA with a 2.5 4 cyl. is doing the same thing, but I haven't done all to it that I've done to the '86. HELP!

Responses

LeMan Bio 8/14/99 20:56

No offense intended, is there oil in the motor? Any oil pressure?

LeMan Bio 8/14/99 21:00

Sounds like you have the cooling system covered so maybe the motor's not as hot as the gauge says. Have you checked the sending unit? Is there a sending unit on an 86? Does the motor seem that hot(270F is beyound hot)? I don't no what the heck I'm talking about but I like to throw out ideas. Good luck and keep us posted.

- 8/14/99 22:11

LeMan - thank you for taking the time to think about it, oil pressure is about 3/4 of the gauge and I just changed the oil, the engine is definately getting hot, I kind of caught the conduit on fire because it got so hot, I think I'm in need of another 3.0, but maybe there's hope.

Huey Bio 8/14/99 22:42

This is a long shot, but could there be something in the block like maybe an old freeze plug that someone changed and instead of pulling it out they pushed it in? Now it has moved into a spot that it is restricting the flow. Just a thought.

BA Bio 8/14/99 22:51

It sounds like you have the water/coolant end of it covered. What about airflow? Is there a fan shroud? Is the radiator clean? Try blasting the radiator with a strong stream of water from the engine compartment outwards. What about timing and air/fuel mixture? At this point, you might want to take the car to a diagnosis specialist repair facility and have them hook it up to their machines. Explain to them what you have done so that they will look for a specific cause rather than just a general overall condition.

Stevie Ray Bio 8/15/99 1:46

Those sidewinders are a bear to get purged, did you completely run it up to temp. before putting the radiator cap on? It sure sounds like you have air trapped in there someplace. This might be worth a try, park or jack it up so the front end is as high as possible to get all the air to migrate to the radiator while running it with the cap off. On my Grand Am I drilled 6 small holes on the thermostat to help keep the air from getting trapped. Good luck and keep us posted.

padgett Bio 8/15/99 13:19

Two things to check first: run till it indicates silly things, shut off. You should feel coolant boiling (sort of a vibration ) in the upper hose. The hose and the fins on the radiator (watch out for the fan) should also be hot. If either is cool then it soulds like a flow problem. If hot then the problem is up front. Any chance of a rag/debris between the radiator and the a/c element ?

- DFS 8/16/99 12:17

Check for an exhaust leak into the coolant. That will cause a hot temp. Also, at 270, the radiator cap should have the coolant blowing out. So 270 is not possible unless the cap is changed to a higher pressure >20 psi. 250 F would cause the radiator to blow. So 270 is wrong. Also the oil would break down very quickly. Recheck again.

- 8/16/99 18:00

Well, I now have a crack in the radiator, *grr* and it does go above 250, and it is blowing coolant out the cap, 13 lb. cap, if I run it with the cap off, at about 160 it starts spitting coolant out the radiator fill neck, tired of getting burned, think I might just replace that 3.0 with a TPI 3800 I have around.

- Homer 8/17/99 7:33

Had anacquaintance with a similar problem on a Cavalier. After only a few minutes of running in the shop from a cold start it would run 220 . Turned out to be a bad O2 sensor. It's worth a shot since it sounds like the cooling system is in order.

Roar Bio 8/17/99 7:39

WHATEVER U DO DONT DO AS BA suggest .Oh man, steam the radiator with water, you would destroy the whole radiator and block it completely so now air will not go trough it. Take a compression test of the engine, could be a blown headgasket.

BA Bio 8/17/99 8:36

Roar, what are you talking about? Cleaning the radiator fins with water is not going to harm it! Taking it to a diagnostic specialist is bad advice?

- 8/17/99 9:06

Guys, guys, guys. I've looked over BA's advice here and while he seems to have a different approach to working on cars than some of us, I am not really mechanically inclined, but I do know a few things, Roar, I have performed 3 compression tests, it isn't a blown head gasket or a cracked block or head, on my gf's '89 is was though. i am ready to do anything possible for my '86, tired of driving my truck, I have cleaned out between the radiator, still hot, I did drill 5 small holes in the thermostat, now it takes 35 minutes to get hot, but I don't want it to get hot at all, what gets me, I haven't found any blockage and this started overnight, I shut it off one day, 100 degree temps all day and the A/C on, it never went over 190, not once, then I start it 2 weeks ago and the temp gauge shot skywards like a 455 rocket, I just don't get it..

BA Bio 8/17/99 11:43

Well, if your not mechanically inclined, take it to someone who is and knows what they are doing.

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

..\members/html/4.html8/17/99 12:10

Could this just be a stuck thermostat? Happened once on my shop truck. One day everything was fine. Next day I'm cruising along and look down and the temp gauge is climbing skyward (yikes!). Since I was close to where I was going, I limped it in and let it cool off. It didn't do it on the way home, but I replaced the t-stat just to be on the safe side.

Steve Chin Bio 8/17/99 13:37

Todd brings up a good point. I had a stuck thermostat on my Toyota 4Runner (stuck part-way open). It took FOREVER to warm up on a cold winter day and on hot days it took forever to warm up, but also overheated. Replacing the thermostat made it warm up faster and also prevented overheating...

Roar Bio 8/18/99 1:22

BA this is whats wrong with your advice. (Try blasting the radiator with a strong stream of water from the engine) If you have to much pressure on the water you will flaten the fins on the radiator and block the airflow. If you want to clean it with water spray first some sort of degreaser on the radiator. Let it sit for awhile and just DIP it in water. But to do that you must take the whole radiator out of the car. It sounds like Todd is on to something with the thermostat.

BA Bio 8/18/99 10:04

I wasn't talking about a 1800 psi pressure washer, Roar. Just a garden hose with a spray nozzle works just fine...:)

- 86GrandAm 8/18/99 12:21

I think I'm just going to get a few of the penguins out of the A/C and stuff them between the A/C condenser and radiator, that will keep it cool.

- Meaty 8/19/99 6:46

Grand am-I used to own/drive/repair an 86 Olds Ciera (sorry boys but the wife got the new car then and I got the left overs!)which we bought new. Those engines will typically run hot when idling for awhile but not that hot. DEFINITELY check for a vapor lock in the cooling system! I used to drain mine while up on ramps and refill and remeber warming it up and watching the radiator hose start to collapse! I would make sure you are on level ground and let the car circulate water without the radiator cap on. Also-stick with a 50/50 mix on antifreeze--maybe even a little less. I also ran a 180 deg thermostat in that baby! Car was great-I unloaded it at 150K due to some rusting but it ran like a bear! Sold it to the first buyer because of how nice it ran/drove!

- Steve 8/20/99 12:28

Take it in to a competent shop and have it put on a scanner. I may be one of the sensors telling the computer to lean out the mixture. I had a problem with my exhaust manifolds turning red, it was a bad fan turn on switch, bad coolant temp. sender, and a slow o2 sensor.

padgett Bio 8/20/99 19:53

OK - stupid but cheap department.Start when cold. Remove thermostat. Remove radiator cap. Start engine. Let idle. Watch water in tank-should be flowing as soon as you start and level will probably drop, fill with hose (shouldn't be more than a quart. Wait until nears 200. Verify radiator fins and hose is hot. Let garden hose run gently over radiator so is running over fins. If it doesn't drop considerably in temp, the problem is not the radiator/fan.

- GrandAmGuy 8/20/99 20:09

I just found a huge crack in the radiator, so I'm replacing it again, I didn't say I wasn't totally mechanically inclined, it's just that this one has me totally stumped, I am still going to trap some of the penguins out of the A/C and stuff them between the rad. & A/C cond.

OldsGuy Bio 8/26/99 0:22

are you sure you filled the radiator up all the way? heater on and let the engine run for a while and fill it as it sucks the water in the block? remember the thermostat will open and close a few times so make sure you don't cap it off before its full. just a thought... went though filling my radiator up and finally got it right...

- MRA 8/26/99 9:36

Did it have a water pump installed just before, or after the problem started? Some Buick engines had a belt system that used a reverse rotation water pump, and the only way to tell is to think about what you are looking at when the impeller is looked at. You can't tell from the outside, I know, I missed this on my own V-8 Buick. The smaller engines all use the same bolt/gasket pattern. just a thought.

- Mac dbrm@earthlink.net 8/26/99 15:52

Something no one has mentioned or I missed, does the water pump have the divider plates installed. I have been told if these are missing this can cause cooling problems. Anyone know for sure?

bvr421 Bio 8/26/99 21:24

mac, I dont think a buick v6 has divider plates in its water pump.

- Anon 8/26/99 22:15

Almost sounds like the thermostat is in backwards.

P455 Bio 8/27/99 22:31

drilling the thermostat is a good way to burp the system, but it does tend to slow the warming process. I usually take a new thermostat, manually open it a bit and wedge an aspirin tablet in it. After the air bleeds and water dissolves the tablet, the therm works as designed.

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- overheating problems? - ira Bio 10/15/99 7:47

I am rebuilding a mild 74 455 and wondering how many of you have had overheating problems? I'm trying to decide if I should spend the money on a aluminum radiator. I live in Louisiana and it get really hot here. Would a 4core and electric fan do?

Responses

FritzCat Bio 10/15/99 9:12

Wait to see if you HAVE overheating problems before you spend money on parts you may not need.

- sugardog @flash.net 10/15/99 9:20

I live in the Houston TX area, and my more than mild 455 (TH400 & 3.42 gear) has not suffered any overheating problems. I have a four-core radiator, stock clutch fan, and aluminum Flow-Kooler water pump (which prob does not drop temps, but does shave a bit of weight off the nose).

jb69fb Bio 10/15/99 21:47

I have a 4 core and electric fan with HD clutch fan ($80.00) Still gets real hot at idle , run cool while driving

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- Overheating - stevens Bio 11/3/99 17:25

I went through the archives and can't seem to find an answer to my problem. I have a 69 GTO convertible I bought about a year ago. The engine was out of the car at the time and is the original (numbers matching). It is a YS 400 - 350hp with #62 heads with TH400. The engine machine work was already done and the cam, crank and pistons were installed. Pulled the cam (067) and the bearings were new. Pulled each of the main caps to check clearance and all were within specs. Crank was turned 10 under per owner. The cylinders had not been bored (113k on car) but did have a crosshatch on them with a small ridge at the top. Had a standard cleanup of the heads done. New: 80# oil pump, lifters, push rods, timing chain. Running headers with 2-1/2" pipes and Flowmasters. Did the standard run in for the cam and the car seemed to run fine for a while. Then an overheating problem developed and IT IS DRIVING ME NUTS! Cooling system rundown: rebuilt water pump (changed twice - the 2nd one had short fins and I thought that might be the problem), new divider plate, new 4 core radiator, new hoses (spring in lower one), new 15# cap, 7 blade fan with new severe duty fan clutch and both 160 thermostat or just the disk with the guts removed. When I had the water pump off the 3rd time, I ran a water hose through each sleeve and got an immediate return through the intake and the other sleeve. Timing is 8 degrees BTDC @ idle (900rpm). Vacuum advance is working. Dwell is 30. Pressure tested the system and got about 5-6# tops. What else is there to check or replace????? HELP! Thanks. Eric

Responses

- Michael 11/3/99 17:27

What kind of temperatures are you talking about here??

Steve Chin Bio 11/3/99 17:33

Also, by what means is the temperature being reported? Under what conditions (idling in park, idling in traffic, going from stoplight to stoplight, freeway cruising)? When the heads were off, did you check the water passages in the heads and block for corrosion? Did you check the ignition timing with the vacuum advance connected or disconnected? Does the temperature come down at all if you turn the heater to maximum temperature and turn the blower motor to full?

lemansdan Bio 11/3/99 18:06

Eric, you got 5-6# on pressure test? Or is that a typo? That's not enough pressure. It should hold at least whatever your cap is rated for (15#), unless you got a leak somewhere.

stevens Bio 11/3/99 18:06

The temp. gets to about 200 within 10 minutes then goes to 240 within another 2-3 minutes. I shut it off then because I'm chicken. Temp. is checked with an aftermarket underdash gauge reading to 280. This is idling in park with about 70 degree ambient temp. At 70mph on the highway it drops to 180 but quickly comes back up after stopping. Looked inside the block and heads and all seemed relatively clean. Timing was with advance connected. Haven't tried running the heater yet, but I do have a working heater control valve so I should be bypassing that part of the system now? I'll try the heater tomorrow.

- Michael 11/3/99 18:10

Are you using a fan shroud, and how about a recovery system??--Michael

Steve Chin Bio 11/3/99 18:14

You have an air flow problem because you have normal temperatures on the highway. Michael is right: A fan shroud will help a lot.

lemansdan Bio 11/3/99 18:20

Eric, I always set base timing with vac advance disconnected.

geo Bio 11/3/99 18:27

Hows the guage? Even new ones are sometimes bad.

Steve Chin Bio 11/3/99 19:05

Egads... I didn't catch that, lemansdan. Yes, with the vacuum advance connected, you cannot precisely set the initial ignition timing. Disconnect the can, plug the hose, then re-set to 8 BTDC @ 750 RPM. Right now, your ignition is probably terribly retarded and that will lead to mixture burning far down into the cylinders, causing an overheating condition. SMACK me with a bent pushrod.

- Michael 11/3/99 19:19

Might be way off base but....with low pressure numbers when you pressure tested the system (are the psi's stable or do they gradually fall off) could they be indicating a blown head gasket or even a crack in the block or head? Do you have any white smoke out of the exhaust pipes?.........Wouldn't coolant in the combustion chamber give cooling problems too?? Anyways, definately recheck your timing--Michael

obeid Bio 11/3/99 20:34

Make sure vaccuum advance is hooked to ful time manifold vaccuum, not ported.

stevens Bio 11/3/99 22:18

I do have a fan shroud and seem to be moving air because a piece of paper held up to the outside of the radiator sucks up to it. I think the gauge is right because the temperature was checked by another method and reads the same. Will double check the timing.

- Michael 11/3/99 22:25

OK, now that we have covered all the big stuff, lets look at the small sh:t.....What are you using for coolant? How far is the fan into the shroud? Are you sure the fan is running, even though the clutch is new it many not be working properly. Don't want to get into another coolant flow debate, but have you tried a higher temp thermostat, say 180 degrees? --Michael

Roar Bio 11/4/99 1:27

Well its a known fact that a Pontiac engine is hard to get all the air out of when you fill water into it. Fill let is sit and fill again. Start engine stop it and checkh. It could be so simple u know or your termostat isnt working correct. And is the termo clucth working OK.

- Mike Garrity boys400@gateway.net 11/4/99 12:57

You are sure the vac advance is working? When I had to switch carbs the morning of pontiac days, when I got out to the track the car was hot, and it never runs over 170. I had the vac advance hooked up, but when I pulled the line off, I noticed the engine did not change, and the vac spot that I plugged into was not pulling a vac. So when I fixed that the temp came down again. Probably not it, but worth looking at.

jktb Bio 11/4/99 18:02

I have brought this up before and didn't have any comments. I have seen several Pontiacs show high temps. at idle in gear(auto trans). 600-700 rpm. Put it in neutral bump the rpms up to 900- 1000 and temperature goes back down quickly. Seems the water is not circulating in the intake, bump the rpms up and the cool water from the radiator cools it back down. If you are overheating at idle only, bump you idle rpms up and see if that helps. Then, maybe someone will have a solution.

stevens Bio 11/5/99 20:49

Okay, heres an update. The timing at idle is the same with the vac. adv. connected or disconnected and plugged. The advance is working because the timing light was on the marks when the engine was revved and it showed advancement. Tried the heater and the temp. dropped by only 5 deg. or so. Coolant is 50/50 mix standard antifreeze/water. Fan is about half in - half out of shroud. Tried bumping up idle and the temp. dropped about 10 deg. immediately but came right back up within 10 seconds to original temp. I think I have all the air out as I have checked the level 4 or 5 times and it stays the same. Seems there was a lot of talk about the fan clutch, so I swapped in a 6 blade flex fan, also half in - half out of the shroud. Now the temp. goes to 208-210 max. with either a 160 or 195 thermostat or 200 with no thermostat. Does this mean I have a bad fan clutch? Also, is this the correct relationship to the shroud for a flex fan? I have about 2-3 more inches between the fan and the radiator and could use a longer spacer to move the fan closer.

Steve Chin Bio 11/5/99 22:30

Eric, half in/half out is a good relationship for the fan. Anything from one quarter in/three quarters out to three quarters in/one quarter out is serviceable. Because the temperatures came down significantly when you changed from a clutch fan to a flex fan, I'd say that your clutch wasn't engaging fully and not moving enough air (been there with a new clutch once). Another thing to look at is your vacuum advance. It seems that it isn't working, unless you have TCS (I don't think '69s had TCS, did they?). Are you drawing manifold vacuum for your vacuum advance source or ported vacuum?

obeid Bio 11/5/99 22:35

Stevens, you say the timing is the same at idle with the vac adv connected and disconnected, but it does increase when you rev it...this is ported vaccuum. Try hooking up the advance can to a FULL manifold vaccuum source, one that will give advance at idle. This will increase the idle speed and smooth it out a bit. Adjust the idle speed back down to where you had it before and recheck your overheating situation. I bet the temps will drop, or at least take longer to get to 210.

bvr421 Bio 11/5/99 22:39

69 was the first year for TCS at least in B bodies with (gag) ported vacuum and complicated vacuum switch and two vac cans on dist. If its been fiddled with it may be that the wrong can is hooked up. Either way if the advance can is not hooked to full vac at idle it will be relatively retarded, that was what the other can was for. The engine would get to 220 and the vac switch would allow manifold vac to the other side of the can thereby increasing dist advance at idle to increase idle speed and cool those jets.

- 70GTO 11/6/99 9:22

stevens, you made the right move by switching to the flex fan, it will move alot more air than the clutch setup. Something stuck me in your last post; you said that the car runs at 210 with the stat in place (either 160 or 195), but, pull the stat and the temp drops to 200. This indicates that there is a flow problem in your cooling system, by pulling the stat you increased the flow in the system and cooled the motor. Now try a high flow stat (180) and see what happens. Also check the speed of the water pump if the pulley speed has been lowered via changing the drive or driven pulleys for some reason you may not be pumping the coolant at a high enough flow rate. By using either a larger crank pulley or a smaller water pump pulley you can speed up the water pump, just be carefully here, too high a speed will also cause cooling problems.

jktb Bio 11/6/99 14:55

See, another example of overheating at idle, bump the rpms up and temp goes right back down. I don't think you will have a problem if you leave it. 208-210 isn't that high and if it goes down immediately after you give it some gas, no big deal. It makes me nervous when it does that to my car but it has never boiled over. Changing the pulleys to make the pump run faster will help it at idle but if it goes to fast you will have overheating problems at highway speed.

- azrael 11/8/99 12:28

correct me if im wrong but if the vac. adv. did not change when you pulled it or had it on BUT changed when reved couldent that just be the mac. adv.???? put the light on the mark and suck on the line without the moter being reved and watch the mark.

bvr421 Bio 11/8/99 12:32

Might want to double check that the timing marks havent slipped around on the crank dampener, its not unusual and could be showing 10 advance when its really 6 retard.

- Meaty 11/8/99 15:20

I think you guys are too used to modern day cars idling in traffic with 100 degree air temp and the needle never moving above 190F!! These are old pontiacs boys--they always ran a "tad" on the hot side!

- Azrael 11/8/99 15:58

Meaty my 455 never goes above 200 in a trafic jam in the middle of JULY and I live in the arm pit of the world. MO.

Steve Chin Bio 11/8/99 19:35

Mine never sees the high side of 165 degrees F... Stock replacement 3-row (hecho en Mexico) radiator, HD clutch fan, Earl's 41910 oil cooler, grilles blocked off with driving lights. Sitting in traffic doesn't affect it at all, and driving at high speed is easy.

- Jack Ambrosiani jack.cygnus@sandpoint.net 11/8/99 23:29

Have you checked for fin-to-core separation in your radiator. If you take your radiator out of the car and the sides are slightly bowed the fins may have separated from the core rods but are just resting infintesimally close to the core rod. This will reduce the heat transfer from the core to the fins by 35 percent and subsequently from then the fins to the air. Take care ---Jack

- Tim's 79 11/9/99 16:29

I too had an overheating problem. I TRIED IT ALL! Thermostats, wetter water, RV fan clutch, pusher fans, shroud, hoses, etc... Want to know what solved the problem ONCE and for ALL, a BE-COOl radiator. Had to bite the bullet for $525.00 but right NOW I run 160 all day or 180 with the air on (thats 180 and 200 in Phoenix in August). If you're overheating in November, you have a serious problem somewhere.

obeid Bio 11/9/99 22:31

Yeah, global warming.

Topic: 12931

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- timing chain covers? overheat - Greg gsulliv1@rochester.rr.com 11/22/99 16:32

I pulled the timing chain cover off of my 400 pont today. It was the one off my 301 i was using. I compared it to a 74 400 cover i got at the junkyard. they appear to be identical. The only difference is the timing indicator is a plastic piece on the 301. Is there any other diffence in them? I was overheating and believed it was the cover. Now i think it was a timing problem with the vac advance.

Responses

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

http://www.pontiaconline.com/members/411/22/99 16:50

Timing covers from 70-something up to 81 are all the same except for the timing indicator variations. You do have the metal plate and the tube inserts between the water pump and the timing cover, don't you? (and these parts are in good shape?).

- Greg gsulliv1@rochester.rr.com 11/22/99 17:43

Yes i do have those parts in. I thought maybe i forgot them but i didnt. here is what my motor is please take guesses on overheating it annoyes me to hell. 74 block 30 over. cast pistons. stock rods. stock crank 20 under. had a holley dominator. 670 heads. 068 cam. holley ignition setup(w/o the HEI). 4 core radiator 2 14" perma cool fans. spring was in my lower hose. 160 degree thermo. holley 750. 10-12 degrees initial timing. never hooked up the vac secondary. every time i tryed it sent pops out the exhaust. i ran strong 14.4 in 1/4 th350 3700 stall. 3.08 gears. i also had the heater core bypassed, ran hose from rear corner of block to timing cover. I had a good radiator cap and a recovery system. I ran about 220 degrees and every now and then would go up to 240 that made me very nervous. I am taking the block into the shop this week i will have them check my coolant passages. i wonder if previous owner put block hardner in them? they look ok to me though. Assuming they arent block please guess what is wrong. Thanks

Steve Chin Bio 11/22/99 18:11

What's your ignition timing like (initial, mechanical, vacuum)? Mixture problem, perhaps? Slipped ring on the harmonic damper, perhaps making the ignition timing read wrong? Hook that heater core up, as bypassing it just lets hot water flow VERY fast out of that passenger side head into the water pump. The heater core adds a bit of a restriction (OK, not a lot, but a little restriction in that department can help).

- Greg gsulliv1@rochester.rr.com 11/22/99 22:18

The mechanical advance would be whatever i stock HEI allowed for. I used a crane recurve kit with the medium springs. It overheated before the recurve as well. the balancer is new from a pontiac dealer. Thanks

- 11/23/99 10:17

From reading your post, it seems like your running two electric fans...are you running the stock 7 blade fan and shroud as well?

- Greg gsulliv1@rochester.rr.com 11/23/99 10:30

I am not running the stock fan or shroud. the fans are being used as pullers. the radiator never really gets that hot so the fans are doing there job i assume. Thanks

Steve Chin Bio 11/23/99 13:19

OK, dumb question time (because I recently went through this): How old is your radiator? I had an old radiator in a car that ran hot, but the radiator never felt all that hot. Turns out that the tanks and tubes were calcified, severely reducing the thermal conductivity of the radiator. A new radiator solved that problem.//Another stupid question: How's your vacuum advance set up (i.e. ported or manifold vacuum, how much advance does it provide, etc.)?

- Greg gsulliv1@rochester.rr.com 11/23/99 22:51

my radiator is brand new first thing i replaced. My vac advance was tried off both neither worked right. sent pops out exhaust so i left it unhooked and didnt plug the dist vac advance tube. could my compression just be too high and that cause heating problems What is the diffence between ported and manifold vaccumm i am not positive i accurately know the difference? thanks

Topic: 12975

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- Overheating 400 - Paul PJDUTO@EXECPC.COM 11/25/99 3:37

I have a 1974 Pontiac Trans Am with a 400 and a turbo 400 A/T. It's bored .10 over with a 216/226 cam and headers. Recently I swapped the 4X heads for a set of 13's. I had a 3 angle job done on them and they were milled .006. I used a performance all copper gasket, .062 thick. The radiator is good, the fan is working ok, water pump is pumping well, good flow to the radiator from the thermostat housing. It will idle forever but when I drive it, the fluid overheats and comes out the overflow tube into the resevoir and spews out the top of the resevoir. I put a new radiator cap on with no help. Anyone got any ideas? Thanks!

Responses

- Paul PJDUTO@EXECPC.COM 11/25/99 3:39

Additional: It is the right gasket for the engine-first thing I checked. Doesn't appear to be an air bubble either as the flow is pretty good to the radiator thru the top hose.

Roar Bio 11/25/99 4:18

Did you flush the heads before you installed them ? And was the engine Ok before you swapped heads ?

JB Bio 11/25/99 6:38

Does the lower rad hose have the spring in it....What are you running for a thermostat?...........JB.

- Cliff ruggles@stargate.com 11/25/99 7:40

You have the same problem as many other owner/drivers of high compression Pontiacs on pump gas. Couple of things to check: You said the radiator is good, is it new or a used flushed out unit? Is it 3 or 4 row? Are you running a 50/50 mix of anti-freeze and distilled water? Did you degree the camshaft upon installation? Incorrect cam timing will cause the motor to heat up when driving. Also many of the new grinds available are aggressive in comparison to the earlier Pontiac cams and will build a lot of cylinder pressure in high compression engines. How much ignitition timing are you running? Initial plus mechanic plus vacuum. Late model H.E.I.'s have way to much for a high compression engine. Did you replace the rubber seals in the timing cover where your metal waterpump plate seals? Is the plate in good condition? Just some ideas. Good luck!

- Ivansta 11/25/99 10:33

Not to sound like an idiot,but have you checked the belt tension,fan could be slipping at higher speeds

- MRA 11/25/99 11:39

First thing 50/05 is not the best to use for a coolant mix, 30 percent antifreeze, 70 percent TAP water, not distiled or demineralized water. Distilled water has no inhibitors within its structures and demineralized water will begin eating minerals, like aluminum, cast iron, etc. The .062 gasket leaves the quench area way too big, and that allows the mixture to be blown out of the quench area, causing detonation, and increased water temps. If the piston decks are low in the block, instead of at zero or so deck, then the quench problem will be aggravated. The other questions posed here are also in need of checking, as any of them could add to the problem(s).

joe B Bio 11/25/99 21:21

get a new 4 core rad,jo b.

- Paul 11/26/99 2:15

To answer the above questions, in order:The heads were not flushed before installation. Prior to the new head installation, the engine would heat up to about 220 f before going to operatin temperature. The lower hose is working fine. I am running a 160 f thermostat. I don't hear any detonation under the hood, nor any pinging. It's the original radiator, but all the cores seem to be hot all the way down. Fan tension is OK. Timing could be a problem. The person who timeed it for me brought in all the davnce right away. Any suggestions on where to time it? Thanks for all the responses!

Roar Bio 11/26/99 3:33

Ok it sounds to me that you allready had a heating problem before you swapped the heads. You say that it works fine under idling. So basically the cooling system should be pretty good. Just a little ? you have the fan shroud in place ? First when you run the car you need all the airflow that you can get trough the radiator. You arent missing some baffles that are placed in the front, so the air will go trough the radiator. It sounds to me that you are out of air when you load the engine. Sometimes it will help to put in a better fan, but it shouldnt be neccesary as long as all the airflow goes trough the radiator and not on the side of it. Check that one out first. And then adjust timing if you have to.

- Ivansta 11/26/99 14:38

A simple mod that I made was to install one of those bongs?not sure what there're called,the fitting that the heater core hose attaches to on the rear of passenger side head,well add one to the other side and tee it in with the hose going into the head,none of my engines ever run hotter than 185 on the hottest day,might help band-aid your problem a-bit

Steve Chin Bio 11/26/99 21:52

Paul, how long does the engine take to get to temperature? If it takes a long time, you have a stuck or partially stuck thermostat. I run a stock replacement 3-row radiator with an oil cooler and coolant recirculation from both heads tee'd into the heater core, and my engine never sees the high side of 165 degrees coolant temperature. If this is the original radiator, carefully consider replacing it with a new one. I recently found that I had a clogged/bad radiator that was warm to the touch and had a little cooling problem at speed. Replacing the radiator fixed that problem.

birdman76 Bio 11/27/99 21:50

simple test for ya it worked for me! you changed from low compression heads to high compression heads, so what i did was went and got some cam2 racing fuel and tried it, low and behold my temp went down and stayed down,as long as i ran cam2. your compression is too high for the street gas no matter what kind of cooling you use, the best band aid is racing fuel or a gas additive like 104 octane boost it works ok with timing retarded i have #12 heads witch are the same as your except mine are for 4 speed yours are auto when i rebuit my motor i got dished pistons that put me about 9:1 comp witch worked out great i can run 93 octane or even 86 if im careful! but i guarantee this is your problem trust me i bought a whole new cooling system for mine before i was a beliver just dont fall in the same pit!

Topic: 14837

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- "Overheating" tip - scott66cat Bio 2/14/00 14:09

After dealing with a 'phantom' overheating condition from my recently rebuilt '66 389, I thought I would pass this along. If the engine doesn't show the traditional signs of running hot...you've checked/rechecked coolant flow... and tested/replaced thermostats, temp sender wiring, temp gauge and wiring, grounds, temp senders, radiator caps, hoses, timing, etc.... but the gauge STILL reports unusually hot temperatures...try unscrewing the temperature sender a little! The 'phantom' heat just may be the result of the sender element being too close to the interior of the intake. In my case, the problem started as poor circulation coupled with this 'hot' reading. A new timing cover fixed the coolant flow issue, but we couldn't figure out the high temp reading. In desperation, I tried backing out the sender until coolant bled out, then tightened a turn to make the seal. Problem solved! Thanks to everyone who participated off-line on this problem, with special thanks to Steve Chin, Witchdoctor, Bob Golenia, and Ron Rocchi.

Responses

77ta Bio 2/14/00 18:43

the pontiac over heating problem solved finally !

scott66cat Bio 2/14/00 18:49

77ta, if only it were true! Just one more thing to check before you pull out your hair..

MB Bio 2/14/00 18:52

It's so simple I could kick myself.Doooh!

- 2/14/00 23:50

So what was up with that? Do you think the end of the sender probe was touching solid iron or was to much torque distorting its ability to expand properly? Sounds like a great ending to a long investigation. Have you ever done a comparison between two gauges?

- Aaron 2/14/00 23:58

Has anyone ever done a comparison of engine temps (as read on the gauge) from running pump gasoline to running pump gas with a lead additive? If everything else was the same and the engine was running properly on the pump gas alone (i.e. no detonation, etc.), I suspect that you might see a few degrees drop in temps since unleaded gas burns hotter than the leaded stuff these cars were designed to burn in the 60's and early 70's. Any facts to verify this out there?

Jerry Coffee Bio 2/15/00 10:02

That is correct, my man. The 1961-63 intake manifolds use a sending unit that has a shield around the bulb. The keeps the bulb from contacting any metal and giving a false reading. The correct sendng units for those intakes are made of stainless steel and are very, very rare. The brass ones are not worth spit and look "aftermarket" besides.

- Paul 2/15/00 12:56

Ok, boys. I spent a few bucks for an Autometer 2 inch face temp gauge for my '67 Goat, and screwed it in where the idiot light sending unit was. Don't remember what the end that I can't see now looks like, but the part that I can see looks like brass. Jerry, do I have an inferior product here? What is the likelyhood of a false reading as suspected in the other posts above? What is the best or proper way to verify the temp gauge reading? Can you leave your radiator cap off and stick a good thermometer in there and watch both and see if they hit 212 simultaneously? I have always suspected that I have a high-reading gauge. Thanks in advance to all who respond.

Steve Chin Bio 2/15/00 15:32

Paul, the cap is on the "cold" side of the radiator, so if you see 212 degrees there, the outlet from the engine will be significantly hotter than that. I tested my gauge/sender combination and they're pretty accurate. I used a Type K thermocouple and a voltage decoder to read the output of the thermocouple. The thermocouple was shoved between the water neck and the hose, bent into the middle of the flow and sealed to the water neck and hose with some RTV. Later, I drilled a pipe plug, glued a thermocouple into it, and stuck that into the intake to repeat the test. Same results.

scott66cat Bio 2/15/00 20:27

To the poster at 2/14/00 23:50 - I'm really not sure if the replacement senders I bought were longer/taller, or if some other force was at work. All I know is that by reversing out the sender a little, my temps went back to where they were previously. I think what tipped us off was the fact that the gauge would report 215-225 relatively quickly, but after turning off the car for about 30 secs and then restarting, the temp would read around 180, then climb immediately back up and stay at 215-225. There's no way the coolant temp would cool that far and fast if the 215-225 reading was accurate in the first place. To answer the second question, I did not try a second gauge (but that was the next plan!). Jerry - do you know of ANY aftermarket gauges that are shielded, or any that seem to provide better readings than others?

Witchdoctor Bio 2/15/00 21:07

Well done, Scott. I learned something, which is the true value of this site, as opposed to fights over head flow. WD.

Jerry Coffee Bio 2/16/00 4:26

I haScott...I have never found any of the brass sending units that had shields on the bulbs. I have some original GM stainless steel sending units for the 1961-1964 intakes that are shielded. There are a couple of part numbers that HY-Grade had for the sending units and some had the shields ans some did not. HY-Grade units are plain steel and not brass but they are not stainless steel.

- Bob Golenia robgol@ais.net 2/17/00 15:47

Scott, Was there teflon tape on the sender threads ? I sometimes use that stuff w/o thinking about how it interferes with the flow of electrons :).

scott66cat Bio 2/17/00 16:06

Jerry - thanks for the options. If my current junk-o sender craps out on me, I may look toward a shielded one to replace it.// Bob, there wasn't any tape on the sender (it's one of the first things I checked for :))

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Topic: 15354

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- Overheating Prevention Trick? - Eric meeks@web-o.net 3/5/00 12:46

The head not connected to the heater box runs almost 30 degrees hotter than the other head. And the primary source of engine detonation is focused in this head. Steam pockets, poor coolant flow, etc. The trick: install a hose fitting in the both heads, tee the heater heads together prior to entering the heater box. The even coolant flow in both heads prevents steam pocket formations and greatly reduces detonation. Well, thats what I was told. What do you guys think? Is it worth a try?

Responses

- eric 3/5/00 12:49

oops, heater hoses

formula 455 Bio 3/5/00 12:53

this is interesting. i dont run a heater box and have both heads without any nipple for water hose bypasses. i was thinking of putting nipples on both heads and routing back to the water pump outlet, but just never did it.

Bob Dillon Bio 3/5/00 13:05

Eric, it sounds like it makes sense. What is the source of your information re: difference in temps?

- Eric meeks@web-o.net 3/5/00 13:13

A local machinist in Bremerton Washington told me the trick. He said in a pontiac, you will find most broken rings in number 5 and 7 cyclinders. I did not ask him where he got 30 degrees from. It sounded convincing to me.

Jim Hand Bio 3/5/00 14:08

Eric, Why would bypassing coolant from the hottest part of the heads aid cooling? It may be possible to lower the temperature of the coolant by bypassing the hottet part of the heads, but I am not sure that is cooling the engine better! The designed flow pattern is through the block and then into the heads through specially located and sized holes. It is then returned to the punmp via the intake crossover. The entire system is designed to maintain a certain pressure from the pump so as to force coolant around and close to the cylinders/chambers. When we place additional openings in this closed system, we lower the pressure. Any coolant you divert from the rear does not pass completely through the heads so you may leave more heat in the heads then if you did not connect the bypass! Just some thoughts for you and the board! All opinions on this subject welcomed. Jim Hand

- Eric meeks@web-o.net 3/5/00 14:11

What if you reduced the size of the metering hole in each hose fitting so that the total flow would equal that of one fitting?

69tempest455 Bio 3/5/00 15:49

What if you plumb both of the rear water ports to the to the water crossover just below the outlet to the radiator. Wouldn't that give extra cooling to the rear of the engine and not lower the pressure in the engine and heads

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

http://www.pontiaconline.com/members/43/5/00 18:49

I dunno. None of mine overheat.

Greg Minor Bio 3/5/00 19:02

two words ALUMINUM RADIATOR.

Ivan Bio 3/5/00 20:29

I tee them together with no problems,hasn't hit 190 degrees yet

Jim Hand Bio 3/5/00 20:43

Ivan, You may have missed my point: Even though the coolant is coming out of the engine at lower temperature, have you actually cooled the hot spots around the cylinders/chambers better or is it even hotter there as a result of the bypass? Jim Hand

- Eric meeks@web-o.net 3/5/00 21:06

Jim, You have me wondering now. I went out and looked at the deck of my 455 block. I was thinking that GM might of made the coolant holes smaller on the side the heater coolant is pulled from. (thinking that it might even the flow out) I did not see any size difference. Also, the coolant from the block comes up into the head from around each cyclinder. It seems like without some extra force to push/pull coolant into the back of the head, the coolant flow will be very slow. What about a test? Installing a temp gauge on the side of each head before and after the tee modification, weld in and redrill the metering holes in the fittings so that the combined flow will equal that of one fitting. (so as not to effect the original design of the pump/coolant flow)

Gears Bio 3/5/00 21:45

Why don't you try installing a water PRESSURE gauge at the strategic points in question and see if there is a significant difference. Your engine was designed to run with a heater core. I have heard the argument that it robs the engine of coolant before, but I suggest using it as a second radiator yields genuinely better cooling that is not simply an illusion. I think there are better more permanent solutions though, like an oil cooler. Anyway, I believe the machinist was right. At least in my experience turning the heater full blast on any of the engines I have owned has put a temprary end to my overheating problems on a hot day, and they were not just spurred on by the temp gauge.

formula 455 Bio 3/5/00 22:28

well, i run a 455 bored .060(which i was told i should not ever do), and have 5 racing seasons on it with no problems and never overheating. i have blocked off both rear head water nipples wqith no problems. i run almost 12 to 1 compression with 3.42 gears on ulp with no racing gas with no problems. no matter who you talk to, at one time or another you just got to do what you think is right yourself. i didnt pay attention to anything anyone told me, and experimented my self. accordingto everything i have done, my car shouldnt be street drivable on pump gas, it should overheat after 20 minutes of driving, and my overbore should have by now cracked my cylinder walls. have fun

Socrates Bio 3/5/00 22:46

12:1?....Really?.....With D-port 96's?. How much did you shave off?

Bracket Race Bio 3/5/00 23:08

I reverse cool mine with a shogun pump which pushes water through a tee at the back of the heads (heater nipple in both heads). Water returns to the radiator through the heater outlet on the timing cover. This has proven to work the best for me after trying different variations of flow.

Jerry Coffee Bio 3/6/00 6:27

formula 455...Your 468 CIC engine and #96 heads could run on cool aid with 9.40:1 CR. You better quit listening to other people if someone told you that you have almost 12:1 CR. It is not even high enough to need 93 octane premium pump gas.

firebird76 Bio 3/6/00 21:12

Website: http://members.xoom.com/Joey455/index455.htm

Check on that web page, it's pretty similar to what you're talking about. Supposely that this "technology" is common use in NASCAR. Don't know if it really makes a difference?

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