I have a 91RS and swaped in a 350 everything was fine for about 3 months then one day it started to get hot quicker and cool down slower. When driving around with the A/C on the temp eventually gets to 240* in about 1/2 hour and doesn't cool down unless I am going over 65 mph. Even in cool weather about 70* it will slowly rise until the fan comes on or if I drive over 50mph then it will cool down. This is what I have done to cure the problem and none have worked.


Checked temp sending unit its fine, about 5* off, changed thermostat 3 different times with 180*, twice with a hole drilled in it and once without, put new air deflector on, BECOOL radiator, changedwaterpump, chaged to a lower temp fan switch on at 210* off at 185*, also installed a pusher fan in front of A/C condensor that comes on when the rad. fan comes on I have also checked for vac. leaks and found none and I am using a 50/50 mix of antifreeze.
I have noticed that the fins on the A/C condensor are tweeked and I tried to straighten them the best I could. I don't get it what the f--k is wrong. With all these mods the damn car should be cool as an ice cube. Is it internal motor problem or what? Also I have good water flow through the radiator. SOME ONE PLEASE HELP I put so much time and money in this car and I don't want to get rid of it

 

Have you replaced your radiator cap? I own an 85 IROC-Z and have spent several hundred dollars, both replacing cooling system components and have mechanics check it out. Nothing was wrong, but the car still ran hot. I'm talking in the red. I posted a question on this board concerning this and it was suggested that I replace the radiator cap. I did and that has cured my problems. I was out driving today in mid 90 degree temperatures with ridiculous humidity and it never got above 220, which is the temp our cars were designed to run at. Don't know if this will solve your problem, but for $3.50, it's worth a shot. Good Luck.

 

yes I have changed the radiator cap, hoses. anything cooling relaited I have changed. also i forgot say in the original post that timing is set at 0* BTDC.

 

Bump that timing up to 6* BTDC, should help you some, unspent fuel from the late timing will reignite in the manifolds and heat the water jackets.

Is it you only problem? Maybe not, but should help some.

Thing that gets me here is when you get up to 50mph, she cools down...this would indicate an airflow problem and with a new radiator, that would leave the condensor as a likely culprit.

Just one other thing, you sure that puller (stock fan) is pulling air and not pushing? I recall a guy who replaced a bad fan (on this board) and somehow was able to get the replacemnet fan spinning backwards, he heated up at idle and lowspeeds as well.