[3 Deuce 64]

I pulled my 389 for a rebuild and replaced it with a 455 ( 77 K ) out of a cat that had been sitting 20 years the coolant was still a nice deep green in color. I ran the car for several hours before pulling the motor. No gages but no idiot lights came on for over heating.
What I have done; I pulled the 4 v intake and replaced it with a 65 tri power I had on the shelf. changed the later style timing cover to the early 64/65 style put on a rebuilt water pump ( that I have already replaced with the old one off my 389 because I found the veins on the rebuilt pump were 1/4 inch shorter the the original pump ) other than that everything is the same. the 389 ran between 180 -190 then 210 on a hot day in Parades . The 455 is running 210 -220 and as high as 230 . It actually vapor locked on me last week. Sunday I dove it to Syracuse which was about 110 miles one way . It hung on 220 most of the trip at high way speeds. Stopped by my friends garage yesterday he has a thermal tester with the red dot. checked different locations on the motor and it confirmed my gage though 47 years old is reading correctly. the only place the motor was reading differently was on the heat exchange cross over on the intake and that was reading the same as the exhaust manifolds over 400* .
One question I have is if I block off the cross over will that help take heat away from the top of the motor. either side of the cross over the temp is around 200*
What has me pulling my hair out is everything is the same except the long block. I have flushed the block but it didn't look crusty in the water jackets when I had the intake and timing cover off.
The other question is the intake didn't have a nice clean machine smooth surface there were some pits from sitting open for years . Nothing the gaskets would have a problem sealing but I am getting a surge jerk at lower RPMs under power ( Same dist out of the 389 ran fine ) If by chance I've got a vacuum leak around the intake would that because it may be running lean cause it to run hot . It idles at 600 -700 RPMs but has a sound like when the timing is too far advanced but it's not.
Other than that the motor runs fine yesterday I was doing about 15 mph ( frustrated ) just matted it she broke loose and smoked them into second and until I let off .

I'm not blowing out any coolant either the system is holding it so far anyway

To eliminate the intake I can pull the one off my 65 and switch it that runs fine

[1967Tempest]

Hmmm... You raise a good question:

Will a 455 cool correctly with an 8 bolt water pump. I assume that you did this so the pulleys, etc.. will line up.

Most of the time, if you are moving and it runs warm, that is an indication that there is not enough coolant flow.

If it was at idle, you need more air over the rad.

Whats the t-stat temp?

You could richen it up a little. If it starts to run cooler, then you do have a vacuum leak. Also could spray water near the intake to see if you a vacuum leak.


HTH,
Dave

[GT182]

Don, check the vacuum can on the distributor. Blow into it and see if you can hear air going thru it. I say it's the one thing nobody takes a look at to see if it's working or not. As you know it will affect your timing and cause overheating.

I just found out lastnight that mine is shot. Everything else checks ok for my cooling system, so hopefully replacing it will help my overheating problem... again.

[3 Deuce 64]

Originally Posted by GT182

Don, check the vacuum can on the distributor. Blow into it and see if you can hear air going thru it. I say it's the one thing nobody takes a look at to see if it's working or not. As you know it will affect your timing and cause overheating.

I just found out lastnight that mine is shot. Everything else checks ok for my cooling system, so hopefully replacing it will help my overheating problem... again.

It was working on the 389 so I assumed it was ok not hard to check pull the cap and put vacuum on it. thanks for the reply.

[3 Deuce 64]

Originally Posted by 1967Tempest

Hmmm... You raise a good question:

Will a 455 cool correctly with an 8 bolt water pump. I assume that you did this so the pulleys, etc.. will line up.

Most of the time, if you are moving and it runs warm, that is an indication that there is not enough coolant flow.

If it was at idle, you need more air over the rad.

Whats the t-stat temp?

You could richen it up a little. If it starts to run cooler, then you do have a vacuum leak. Also could spray water near the intake to see if you a vacuum leak.


HTH,
Dave

It gets warm in both situations . I went through my fan clutches and found one with about 3/8 inch longer shaft which would put the fan into the shroud more. that helped a little . I may try shimming the shroud back a bit .
I will try your idea and richen up air mixture.

On the change of the timing cover I have done it in the past and didn't seem to have any problems. the 428 in the 65 is done the same way. I haven't driven it on the road as it's still not finished but we've driven it around the house moved it in and out of the garage and let it idle warms up to 180 - 190 and on a 3 core rad the 64 has the original 4 core trip rad.
I can't believe there is a blockage in the 455 the coolant was too clean and there is good flow across the top of the rad .

[1967Tempest]

Good point on the 428..

Might be the vacuum can or a lean condition. I noticed that when I went from a 2.56 rear to a 3.23 rear, because of the higher RPM's, the car runs 15* warmer..

[GT182]

Don, I did the flush of the engine, radiator, and heater. I got nothing out it all except clear water and the flush solution. Been bannging my head against the wall until I was talking to a couple of guys this past Saturday at a Cruise Night..... they suggested checking the vacuum can. I did and found it was no good. Just got another one this morning to install. I'm crossing my fingers.

I could blow into my old one and hear air passing thru it. Not with this new one.

[geeteeohguy]

A larger engine generates more friction, therefore more heat. If all else is the same as the 389, your cooling system is marginal for the bigger engine, IMO. The fact that it's running 220 at highway speeds indicates a radiator capacity issue.

[GT182]

Don, did you check the vacuum can on the distributor yet? It's something most of us wouldn't even think about.... and it's an important part of the timing.

[My442]

I chased this on a 455 car, and found that the mechanical advance springs were weak, and they allowed too much advance.

Also, it takes an aftermarket aluminum radiator to bring down the running temps to the 185-190 range.

I have never had a factory radiator do that, even recored.

[T A 70]

Originally Posted by My442

Also, it takes an aftermarket aluminum radiator to bring down the running temps to the 185-190 range.
I have never had a factory radiator do that, even recored.

Totally agree...money well spent..

[GT182]

It's funny that back in the days these cars were new and the used ones a few years old, there was no overheating issues and no one used aluminum radiators.... unless I suppose they were drag racing. Even the guys I knew that ran pontiac engines on the dirt tracks didn't have many problems. Problems they usually had were punctures.

The 3 Pontiacs I had back in the 70s.... 66 GTO, 63 GP, and 66 Tempest Custom.... with their original radiators never overheated, even on the hottest days of summer. Not even my buddy's 421 62 GP with the cars original radiator. The owner of the local radiator shop here says it's only because of the larger tubes that an aluminum radiator cools as good as or cooler. Other than that they're no better than copper and brass, and mostly not as good. And he should know.

[T A 70]

Originally Posted by GT182

It's funny that back in the days these cars were new and the used ones a few years old, there was no overheating issues and no one used aluminum radiators.... unless I suppose they were drag racing. Even the guys I knew that ran pontiac engines on the dirt tracks didn't have many problems. Problems they usually had were punctures.

The 3 Pontiacs I had back in the 70s.... 66 GTO, 63 GP, and 66 Tempest Custom.... with their original radiators never overheated, even on the hottest days of summer. Not even my buddy's 421 62 GP with the cars original radiator. The owner of the local radiator shop here says it's only because of the larger tubes that an aluminum radiator cools as good as or cooler. Other than that they're no better than copper and brass, and mostly not as good. And he should know.

Well, you have to account for leaded gas and higher octane fuels in "those days"...both kept engines running cooler...an aluminum rad (Rodney Red) dropped my temps 30 degrees in my '70 Trans Am with the unleaded/low octane gas we have now...

[Old Goat 67]

Originally Posted by T A 70

Totally agree...money well spent..

Have to respectfully Totally disagree. Not needed in Louisiana heat!

[T A 70]

Originally Posted by Old Goat 67

Have to respectfully Totally disagree. Not needed in Louisiana heat!

What's different about Louisiana?

[Old Goat 67]

Heck of at lot hotter than California. 102° right now.

At least the places I went. Not Death Vally of course.

[T A 70]

Originally Posted by Old Goat 67

Heck of at lot hotter than California. 102° right now.

At least the places I went. Not Death Vally of course.

You can't keep the car running cool?

[Old Goat 67]

My 67 GTO runs at 182° max! With a 180° thermostat.

And I do not have an aluminum radiator.

[T A 70]

Originally Posted by Old Goat 67

My 67 GTO runs at 182° max! With a 180° thermostat.

And I do not have an aluminum radiator.

Fantastic...guess you don't need one!

[Old Goat 67]

Originally Posted by My442

Also, it takes an aftermarket aluminum radiator to bring down the running temps to the 185-190 range.

I have never had a factory radiator do that, even recored.

Wouldn't want to make a little wager on that would you?

Originally Posted by T A 70

Fantastic...guess you don't need one!

You didn't either!

It's time to stop spreading untruths and spending other peoples money here.
A properly setup Pontiac will run as cool as any other make, BUT you must do your homework properly to find and fix the problem.

Charles