tony-pr

I have 1991 camaro RS 305 TBI. The engine was rebuilt and bore over 40, long headers and dual exhaust. It overheats only when going up a hill or with the A/C on.
I’d tried almost everything. Fans always on, new three-line aluminum radiator, tried running it with and without t-stat, hose not collapsing, timing is perfect (verified by experts), new water pump. Searched every forum and the web for answers, can’t find anything.
I believe that it is running lean. Checked a spark, looked as lean. Also tested the AFR with a wide band, varied from 14.7 to 16 idling. Fuel pump pressure is 12psi.
Thank you for your help, getting kind of desperate, been almost a year trying to fix this problem.

1987L69

Try an aftermarket temp gauge. just to make sure its overheating. also check your air dam under the radiator, it sounds like an air flow issue.

tony-pr

Thanks for your response. I just got my hands on an infrared gun. I point it at the t-stat housing and when my gauge marks 220+ the gun is in the high 190s (like 198). Is there another place where I should point the gun at?
Also, what I understand from what I found on the internet is that the sensor next to the t-stat housing sends coolant temperature readings to the ECM and that the sensor on the driver side of the engine block ( just under the manifolds) is the one that sends the readings to the gauges, is that correct?