i have a 88 iroc-z and we built this motor it is a mid 70 block 350 bored .60 over 4 bolt main and it has flat tops
well we are poor ******* so i used the original 305 tpi heads to keep the tpi intake system.

The only reason i did all this is because it kept overheating and it eventualy developed a knock.

Now it still overheats and i bypassed everything.

Now all that is running is the motor and radiator off of the cooling system.

I had the heads, intake, and block all checked for cracks and they're fine. Then i had the radiator checked and there is nothing wrong with it.

I have two electric fans that run constantly.

I took the thermostat out because i thought that it was sticking.

I also cut the CAT. out because i thought that it might be plugged.

Even after all attempts it still overheats after about 15 or 20 min. of driving but doesn't overheat at idle.

Any help would be appreciated.

 

start car, and let run. check coolant level for an air pocket.

step one: remove radiator cap
step two: start car and let run
step three: fill with coolant once thermostat opens

not sure if this is problem but it may help you



put the thermostat back in!
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make sure you have lower air dam too (if equipped).

 

Whats your timing at. Many people overlook timing when it comes to cooling issues...retarted timing will cause overheating and advanced timing will cause a knock...

 

timing should not be the problem but i will check i have messed with it for a while
but when we set it we set it like an old gen 1 car we started at top dead center and advanced it till it spark knocked and then backed it off a few degrees