[Post Coupe]

I can't get the temperature on my 65 Pontiac "389", 4 speed, 4 barrel, to run at less that 190 degrees once warmed up! I have installed a fan shroud, clutch fan, and 160 degree thermostat. On very humid days, I get what we used to call "vapor lock", the car stalls out after it is warm and turn off the engine for a little while and then start it up again. It starts ok but stalls out and I have to press the gas pedal to the floor and hold it there until the engine refires. After reading the many posts on PY online forums concerning "67 GTO running hot", I am wondering if the problem may be the 410 posi rear end in my car? At 60 miles an hour I am tacking 3000 RPM's. One of the guys posted that 3.23 gears would make the car run cooler. What is the cheapest way to change the gears in the rear end?

[Post Coupe]

Sorry, iIforgot to mention that rear end is a 12 bolt, not 10 bolt, if that makes a difference.

[Tom Vaught]

Ran around with 4.33 gears for several years in college (using a carter AFB carb and an electric fuel pump and return line). Could cruise at 65 mph no issues except it sucked gas like a drunk sucks booze in a bar.

I would make sure that you have a properly vented gas cap on your car. Do you have headers on your car?

Where is the clutch fan blade in relation to the edge of the shroud opening? Fan should be 2/3rds in the shroud- 1/3rd out of the shroud.

By the way 190 degrees is NOT that hot on a GTO when many of them ran over 205 degrees in the summer in the 60s. Why do you think that 190 is too hot? You will never be at 160 degrees with a "160" thermostat.

Tom Vaught

[Andre]

190 degrees is a goal temperature that most GTO owners would be pleased to attain. My '64 regularly runs at 220 on the highway at 80mph, then cools down to 190 as speed decreases.
On my '66 back in the 80's I chased vapor lock the entire time I had the car. An electric fuel pump was my only bandaid.

[t-bar]

I had the same problem and i am running with a 4;56 its not the gear ! after pulling the motor i decided to tear it down and the front rod and main bearing were almost gone..after new build can't get it over 175.. not saying it bearings but ???
I also had the vapor locking prob. went with earl ss. braided line and moved the line away cured it. but you probably want to keep it original looking.

[regamble]

Generally speaking, no matter what the vehicle, 190 is actually a pretty low temp. Your system is designed to run above the boiling temp of 212 most days, that's why the system has to be under pressure and a pressure relieved cap installed. If you're having vapor locking issues it can be caused by a failing pump, failing or softened rubber line from the pump to carb (which is why originally they all ran steel lines) or even possibly carburetor boilout.

If the car isn't overheating then the issue is quite likely in the fuel system not the cooling system.

[elefantrider]

I think 190 is perfect.. what would you like to attain? What fan clutch are you using?
The factory lock-up type is best. They have a lock-up spring on the radiator side.

[GT182]

Remember? They came out of the factory back then with 190 thermostats in them, so 190 is good. That temp helps clean the moisture out of your engine and the reason 190 T-stats were used.

I'd say that above 210 is where you start to worry. 220 might be ok for a very short time, but no higher. I think Pontiacs can handle the heat a little better than Chevies or the other makes, but not for very long. I got vey worried when mine was reaching temps from 220 to 245. That's when I recored the radiator to an SLK core and started looking onto the water pump and divider plate issues. Luckily it's now just the pump and plate issue causing overheating.

One other thing... only use the green antifreeze. Red when it gets hot or sits long enough [forgot which it was] will start to gel up and plug things up. Charles' son found that out the hard way. Maybe it's ok in newer vehicles but I won't use it in my GTO.... again. Yeah, I made the mistake but caught it fast enough and got rid of it.

[elefantrider]

Steve, can you post a picture of both sides of your fan clutch. I have not had any luck with the aftermarket units that don't have the spring.

[Post Coupe]

Thanks everyone who replied to my thread! I have learned the following; I need to reposition the clutch fan (I didn't order the fan blade spacer when I purchased the fan with clutch) and the fan blade now just meets the shroud when it should be 2/3rds in the shroud, also I need to change fuel lines to steel ones, and I may have to get an electric fuel pump ( just had new mechanical one installed).
I forgot to mention on my original thread that I just had a remanufactured Carter 4 barrel carb installed, it is ideling perfectly (once warmed up) but the car doesn't have that initial quick burst of power like the old Carter carb had, any suggeations?
Steve

[Post Coupe]

Just realized why I didn't purchase a fan spacer because , Year One states that "do not use a fan spacer with a fan clutch because water pump failure will occur, as well as potential damage to the radiator and shroud".

Question, how can I move the fan 2/3 into the shroud without a fan spacer?

Thanks,
Steve

[Post Coupe]

Pictures of Fan W/Clutch.[ATTACH]



[/ATTACH]

[GT182]

Originally Posted by Post Coupe

Question, how can I move the fan 2/3 into the shroud without a fan spacer?

Thanks,
Steve

Steve you shouldn't have too. I've got the same set up and for mine and 3/4s of the fan blade is inside the shroud. Works fine. I got my fan and clutch from OPG but the shroud I got from them wasn't drilled to mount it on the radiator support. I sent it back and got one from Ames which was, and everything is ok. I don't think I'd want the fan too close in case something happens.... not that it would really make a difference anyway. I'd show you a photo of mine but it's all apart for a water pump change.

You could put the AC seal kit around between the radiator and core support. See page 229 in the Ames catalog. Charles just bought the masticated rubber to make his own.... cheaper too. You might be able to find the fasteners at Lowes, Home Depot, or at an auto parts store like NAPA, that has a Dorman parts section.

[geeteeohguy]

Post Coupe, nothing is wrong with your car. Running 190 when warmed up is just fine.

[SD421]

I used to run a 180 thermostat and it would stay right at 180.
If you want it cooler than run the 180.
Running the 160 thermostat is your problem.

Don

[Pecosbill]

I was running the old 3 core radiator in my 64 and it would run hot, especially if I had to sit in traffic. Switched it over to a new 4 core and haven't had a problem since. Nice steady 180, even in the Texas summer.

[Old Bird]

I would be tickeled pink to run at 190 or less.

[INJUNTOM]

Late model, light casting engines run at 230 degrees and do this for 300,000 miles plus.

Reminds me of years ago...My '67 Conv would run 230 no matter what. Even down the road at night. Multiple radiators, water pumps, electric fans, 2 different engines, different gauges, etc.

Damn thing didn't do that until I put a gauge on it instead of the factory idiot light..

[INJUNTOM]

BTW, anybody notice that the large journal motors (428/455) and the small motors (326/350) seem to run cooler than the 400 engines? Can't comment on the 389 as far as my experience goes. Haven't ean one yet, but I do have one on the stand.

[Flatfish]

The pro builder who did my 389 said the engine is suppose to run at a steady 190 degrees and has a 190 thermostat. He said no point in running it cooler.