1979 Chevy Corvette Overheating

BOHEMO2

MEMBER
1979 CHEVROLET CORVETTE
V8
2WD
AUTOMATIC
3,000 MILES

I have been given dozens of reasons for my overheating problem. None of which apply to this engine. Understand that I am pushing 400+ HP with a 10.5 to 1 compression ratio pistons with Vortec heads. The car has 72000 miles but the engine only has 3000 miles. The car is not equiped with any type of poluttion control. (I.E. Cataliytic converter, ERG valve, air pump, etc.) It is carborated with a free flow air filter with a new filter. I have had a number of local Hot Rod shops and muffler shops tell me otherwise than what I am am being told in this forum. I am only trying to conferm the correct answer for my problem.

I repeate, the cooling system circulation has no problems. No vapor locks, No air bubbles, high volume aluminum water pump, NO THERMOSTAT, No bent or crushed exhaust. The ehaust system is only 2 years old but only a 2 inch which was stoke at 195 HP. The L82 Vette had about 40-50 more HP stoke and it had a 2 1/2 inch exhaust.

Who has the right answer?
The local shops around me or you at this forum.

CAN AN UNDERSIZED EXHAUST SYSTEM CAUSE MY CAR TO RUN HOT?

4 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Yes, and it will rob horsepower as well, the engine must breath in and out just like you! A thermostat wouldn't be a bad idea either. Do you have the four core radiator, or the stock 2 core? I had a 79 TA with the four core as stock, and only had a bit of trouble on the hottest days with the a/c on. Check the fan clutch too.

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Friday, August 1st, 2008 AT 6:12 PM

BOHEMO2

MEMBER
23 POSTS

In response to "merlin2021" answer to my question.
His "YES answer but will rob HP" is a start to coming up with an answer to correcting my problem. To clarify his response, I have a 4 core radiator (NEW). I agree that the engine must breath, but if it's taking in more air than it can exhaust, I believe it will create too much back pressure and thus the over heating propblem. I have recently changed the timing from 6 deg BTDC to 12 deg BTDC and this has made a 5 degree difference in the temp and it is even running better.

I intend to go with my original Gut feeling and replace the exhast system with a larger diameter one within the next week and post my results on this forum.

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Sunday, August 3rd, 2008 AT 3:50 PM

MERLIN2021

MECHANIC
17,250 POSTS

That was my answer. With 600 plus HP you do need larger diameter pipes and headers.

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Sunday, August 3rd, 2008 AT 4:11 PM

BOHEMO2

MEMBER
23 POSTS

This is to "merlin2021"

I agree with you about 600HP needing a larger exhaust. I would say 3 inch in that case. But, I contend that if GM put a 2 1/2 inch diameter on an L82 with only 225HP, they did that for a reason as opposed to a 2 inch on a L48 with only 195HP.

Like I said, I intend to go with the 2 1/2 inch and I will let everyone know of the results.

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Sunday, August 3rd, 2008 AT 4:33 PM