[minellix]

What would make the temp rise while driving? A lean condition , change your jetting / fatten it up .

[grivera]

Add to that - poor air flow - like electric fans blocking the radiator. Also, a coolant hose collapsing and restricting flow - like when the spring is left out of the bottom hose

[nUcLeArEnVoY]

Running lean is often blamed for running hot, when in reality it doesn't make much noticeable difference. Usually something far simpler is going on.

The biggest tuning-related issue when it comes to engine temp is ignition timing moreso than fuel delivery. Retarded timing tends to cause engines to run hot since it doesn't allow full evacuation of exhaust gases due to the delayed spark during the compression stroke. I've seen videos of headers glowing orange at idle speed because of retarded tuning.

Slow temperature rise at highway speeds can be normal for some cars simply due to higher RPM = more work and heat generated, but eventually it will level out and stop rising that far past the thermostat temp. But if your engine temp rises out of control at speed and doesn't stop, then it could be a radiator issue, blockage somewhere, restricted airflow, simple case of air in the system, a lower hose collapsing, thermostat not opening, or bad water pump - Pontiacs are special with water pumps in that they need proper clearance between the impeller and divider plate to ensure adequate flow.

Check all the above basics first. In the case of restricted airflow, make sure to see if your car came from the factory with a front air dam. If so, make sure you have it installed. On some cars, it is essential to redirect ram air to the radiator at speed.

[78w72]

way too many variables that cause or contribute to overheating... but if everything is right with the cooling system & tune of the engine/carb, these cars should not be overheating like some guys have, they didnt overheat from the factory in any states or climates from california to florida. even with much higher HP the factory cooling systems should & do support that.

also, the water pump to divider plate clearance trick is a good idea if/when youre in there, but the factory didnt do this & many/most stock engines had pretty big gaps there with no issues of overheating. i had a mild built 455 as a daily driver & daily abused it in hot summer temps, never knew about the divider plate trick back then & never had any issues with overheating... even with a very dirty & repaired radiator leaks that shut off at least a few of the rows. some members on here run higher HP & openly admit they dont clearance the water pump & dont have any cooling issues... in AZ temps! so its a good idea to do that but its not always required for a pontiac to run at decent temps.

[george kujanski]

Out of the factory, I would think that the water pumps were manufactured with the impellers accurately pressed onto the shaft, probably unlike what we get from rebuilders. 50+ years later, how many untouched water pumps still exist?

Is there any evidence that most stock engines operated well with large impeller-to-plate clearance? I doubt it.... that’s contrary to the design of the type of pump. Proper clearance is mandatory for proper operation. In my case specifically, simply reducing clearance made a substantial improvement in cooling.

George

[nUcLeArEnVoY]

Originally Posted by 78w72

way too many variables that cause or contribute to overheating... but if everything is right with the cooling system & tune of the engine/carb, these cars should not be overheating like some guys have, they didnt overheat from the factory in any states or climates from california to florida. even with much higher HP the factory cooling systems should & do support that.

also, the water pump to divider plate clearance trick is a good idea if/when youre in there, but the factory didnt do this & many/most stock engines had pretty big gaps there with no issues of overheating. i had a mild built 455 as a daily driver & daily abused it in hot summer temps, never knew about the divider plate trick back then & never had any issues with overheating... even with a very dirty & repaired radiator leaks that shut off at least a few of the rows. some members on here run higher HP & openly admit they dont clearance the water pump & dont have any cooling issues... in AZ temps! so its a good idea to do that but its not always required for a pontiac to run at decent temps.

I agree, man. So many, so, so, SO many threads on overheating on not only this message board but all enthusiast forums; but you never really do know the whole story from the poster. A cooling system isn't that complicated, and when the parts are there and operating, it almost always remains trouble free as long as its applicable to the motor.

For all we know, this dude could be making 700 HP and enough compression to form a black hole, and yet is using the stock copper/brass radiator that has never been recored after half a century. For all we know, another poster who made an overheating thread has a restrictive E-fan putting out only 1000 or so CFM, or a fan clutch that broke, or is not running a shroud, cuz "they ugleh!" For all we know, another poster has a head gasket leak. For all we know, another poster who started a thread is using GM Dexcool or 100% antifreeze concentrate with no water. For all we know, another poster is running 6 degrees of initial timing without vac advance. For all we know, this dude is blasting AC down the freeway but is running an undriven water pump pulley. For all we know, another poster has been having belts slipping and squeeling like a stuck pig effectively making his water pump just freewheel, and didn't tell us about it...For all we know, a lot of these people aren't even overheating or "running hot" at all by definition!

Like I said, we don't know the full story... and yet here we are splitting hairs and recommending he ups jet sizes in the carb, changes spark plug heat range, or some reachy crap like that. It's usually something far more logical, a lot of it just boils down to lack of knowledge.

[78w72]

Originally Posted by george kujanski

Out of the factory, I would think that the water pumps were manufactured with the impellers accurately pressed onto the shaft, probably unlike what we get from rebuilders. 50+ years later, how many untouched water pumps still exist?

Is there any evidence that most stock engines operated well with large impeller-to-plate clearance? I doubt it.... that’s contrary to the design of the type of pump. Proper clearance is mandatory for proper operation. In my case specifically, simply reducing clearance made a substantial improvement in cooling.

George

out of the factory the clearance was not what guys do today is what i meant, the clearance trick will get that gap to .015-.020. pretty sure they were never like that from the factory. i have changed a factory original pump & it had what most would consider a very large gap. many on here dont do the clearance trick & the gap can be all over the place. FJ may chime in & comment on how hes never done it & has no issues. just saying its not needed for a pontiac engine to run cool but is definitely a good idea to do.

myself & so many others back in the late 80's to early 90's on higher HP engines didnt know about the clearance issue, on my old 455 it was closer to 1/4-3/16", that car ran cool in any temps or situations with a crappy old repaired stock radiator.

[78w72]

Originally Posted by nUcLeArEnVoY

I agree, man. So many, so, so, SO many threads on overheating on not only this message board but all enthusiast forums; but you never really do know the whole story from the poster. A cooling system isn't that complicated, and when the parts are there and operating, it almost always remains trouble free as long as its applicable to the motor.

For all we know, this dude could be making 700 HP and enough compression to form a black hole, and yet is using the stock copper/brass radiator that has never been recored after half a century. For all we know, another poster who made an overheating thread has a restrictive E-fan putting out only 1000 or so CFM, or a fan clutch that broke, or is not running a shroud, cuz "they ugleh!" For all we know, another poster has a head gasket leak. For all we know, another poster who started a thread is using GM Dexcool or 100% antifreeze concentrate with no water. For all we know, another poster is running 6 degrees of initial timing without vac advance. For all we know, this dude is blasting AC down the freeway but is running an undriven water pump pulley. For all we know, another poster has been having belts slipping and squeeling like a stuck pig effectively making his water pump just freewheel, and didn't tell us about it...For all we know, a lot of these people aren't even overheating or "running hot" at all by definition!

Like I said, we don't know the full story... and yet here we are splitting hairs and recommending he ups jet sizes in the carb, changes spark plug heat range, or some reachy crap like that. It's usually something far more logical, a lot of it just boils down to lack of knowledge.

thats a lot of "for all we knows"... but just the same, for all we know its a mostly stock engine or very mild build that just doesnt have all the t's crossed & i's dotted on the tune or cooling system basics. or as many do, they overreact to temps creeping to 195 degrees & think its overheating. the factory used 195 T stats on these cars & frequently they saw 205-210*, thats not overheating but is hotter than most like to see.

i didnt see anyone suggesting changing jet sizes or splitting hairs, the OP asked if a lean condition could be the cause, but like you mentioned that is usually the last thing on the list for reasons an engine overheats. i just wanted to mention the water pump clearance isnt always an issue & these cars ran fine when original or when people increased the HP some.

[Old Goat 67]

Hey guys , for making the degree mark on a keyboard, try this;

Hold the ALT key down and key in 0176, 0r 248

Let me try, ° and °

Yep they both work.

FYIW

Charles

[Formulabruce]

This thread is just bait, but post # 9 was great!

[dataway]

¢¶ƾɇΩπϪѾ֍۞†℗™♂

[Old Goat 67]

Originally Posted by dataway

¢¶ƾɇΩπϪѾ֍۞†℗™♂

Nope, that wasn't it.

But it's 76° F here.

[george kujanski]

Charles, you always have good suggestions.

George

[Old Goat 67]

Uh, you're the one who started that first, a long time ago!

[Goatracer1]

I am old enough to have driven these cars when they were new or almost new. Most did NOT have temperature gauges and I never had a "HOT" light come on unless there was a coolant loss because of poor maintenance or a leaking hose. How hot did the engines run ? I have no idea and nobody cared as long as the light didn't come on. I think if we didn't all use gauges now we most likely would not have "problems" with our engines running "HOT".

[OG68]

Temperature sensor switch for the Temp light was set to 245º IIRC.

[78w72]

Originally Posted by OG68

Temperature sensor switch for the Temp light was set to 245º IIRC.

so if the warning light didnt even come on until 245° (look i made a degree mark!) sounds like GM knew engine damage didnt occur until at least 10-20° above that. so all the guys freaking out about "overheating" at 200-220 is much to do about nothing.

of course that's hotter than most like to see but no need to go to extremes with crazy mods

[george kujanski]

temperature unknown

[68 Firebird]

George that pic looks like it came from the movie Airplane!!!

Gerry

[Formulabruce]

Originally Posted by 78w72

so if the warning light didnt even come on until 245° (look i made a degree mark!) sounds like GM knew engine damage didnt occur until at least 10-20° above that. so all the guys freaking out about "overheating" at 200-220 is much to do about nothing.

of course that's hotter than most like to see but no need to go to extremes with crazy mods

Meanwhile transmissions were COOKING above 200 degree temps.
We replaced transmissions due to engine over heat issues.