nick skrinjar

My 76 has been overheating on the highway, 3 speed auto and anytime its above 3000 rpm the temperature steadily climbs to 250+. In traffic or just cruising around its completely fine and hovers around 200. i replaced the stock rad and fan with a flex-a-lite aluminum rad and electric fan combo.(issues came after this replacement) I know there could be a multitude of issues but the easiest one i can think of is closing the gaps between the rad and the frame to ensure the air coming in at high speed is going through the rad and not around it.

Long story short, im looking for some sort of high heat foam / rubber weatherstripping and adhesive to close these gaps off. any help would be greatly appreciated!

Scottd

Plain old Home depot 3/4 wide foam, one adhesive side, works fine if you want to go the budget route.

Alan 71

Hi ns,
Originally there were pre-cut dense foam strips on all 4 sides of the radiator that sealed the radiator to the core support.
These were vital in assuring that the cooler air was being pulled THROUGH the radiator rather than AROUND it.
Will the kit for a 76 work with your present set-up?
If so they're readily available.
Regards,
Alan

Alan 71

Hi ns,
Originally there were pre-cut dense foam strips on all 4 sides of the radiator that sealed the radiator to the core support. They were different sizes depending on the gap they were intended to seal.
These were vital in assuring that the cooler air was being pulled THROUGH the radiator rather than AROUND it.
Will the kit for a 76 work with your present set-up?
If so they're readily available.
Regards,
Alan

Peterbuilt

You should have an air dam (something like #6).
It helps to push the air up and into the radiator.

rcread

Did you check timing? Does your vacuum advance canister hold vacuum?

keithl1967

How old is your lower radiator hose...
At 3000+ RPM,it might be sucked "closed," cutting off cooolant flow, resulting in overheating...

Big2Bird

The correct hose has an internal spring to prevent just that.
Always check the replacement hoses for that. I have found "correct" hoses from Delco that did not.

fishslayer143

what cfm rating does your new electric fan have?. 3500cfm + is required to keep it cool in warm climates ..

The13Bats

Right on fish...

So when its overheating at highway speeds is the fan off, if yes, can you do a test, run at highway speeds with fan on, see if it keeps cool, if yes, then the foam might just help, if no then the foam likely wont fix it, because its not an air flow issue but ahem, a radiator or other issue.

nick skrinjar

Ive installed the air dam thinking i solved all of my problems but sadly it seemed to have little to no effect.

I dont know if the fan is set up to turn off at higher rpm's, from what i understand it takes the temperature and turns on until the temperature is pulled back down to whatever is set. What your saying makes sense to me because it should be pulling a good amount of air through while on at highway speeds.

Sadly i have had this conundrum for almost 3 years. i have tried a new water pump, installing the air dam as mentioned, timing seems to be correct, lower hose both has the spring and is rather new. Ill look into the foam mentioned above and see if that fixes it on a warmer day in Canada, might take a while to get there mind you. (ive noticed if its below 18 Celsius then the issue almost goes away completely)

SH-60B

I would have thought it was the lack of an air dam also, that was the problem with mine when I first got it.

So take another look at the electric fan. Is it wired properly, not running in reverse polarity? Running in reverse would be able to move air through the radiator backwards at low road speeds, but just block flow at highway speeds.

FWIW, I don't have any of the foam around my radiator at all and it cools a 375 horse motor just fine. (DeWitts with dual electric fans.)

thoyer

Check that the vacuum canister will hold a vacuum. I chased an overheating problem for a while in one of my cars. Found out that the vacuum diaphragm had a slow leak and at steady highway cruise rpm it would bleed down leaning things out.

Beg, borrow or steal a vacuum pump and test it that way.

Tom

BLUE1972

I agree with Allen - if the foam is missing the air will go around the radiator due to higher pressure in the engine compartment. My 71 ran hot without the foam. Now it runs cool with the foam seals. Radiator to Radiator support.

0Tom@Dewitt

So does this mean the dual Spal fans (2760 CFM) do not work?

Metalhead140

https://willcoxcorvette.com/catalogs...=radiator+seal

BLUE1972

Seals from RICKS CORVETTE PARTS fit great and are as OEM.