I have a 88 Camaro Rs with a 305 tbi. The engine seems to heat up pretty fast although it has never actually overheated. Today I let it sit like five minutes running in 85 degree weather and when I checked the temperature it was reading almost 260! I have recently drained the old coolant and put new in and I also put a 160 degree thermostat in it too, but the problem still persists. Does anyone have any ideas on what could be causing the heat? Thanks for your help!

 

Check to make sure the gauge is reading accurately.

 

When you flushed the coolant, did you make sure to put mostly water in the radiator? Do your fans work?