GM-GMC: operating temperature, degree thermostat, oxidation rate

Question
I have a 1983 Chevy 1/2 ton pickup in which I recently installed a rebuilt 350. My temp gage indicates an operating temperature of 220-225. THe engine never gets into the red line area and never seems to be hot. I have a 190 degree thermostat installed. The radiator shows good circulation. Is this consistent operating temp a problem? I also installed headers. Can this be the source of the heat?

Answer
The temperature is good for emission control and theoretically good for efficiency, but motor oil oxidation is a concern.  Conventional (mineral) motor oil starts to degrade when subject to constant temperatures over 200 degrees F.  In fact, the oxidation rate triples for every 10 degrees F above the 200 threshhold.

Your vehicle was originally equipped with a 180 degree F thermostat and I would install one unless you have a specific need for the higher temperature.

Alternatively, synthetic oil can easily handle the temperature your engine is running at.

My advice is based on accurate readings from your engine.  To be certain of the temperature, install a calibrated mechanical temperature gauge in one of the cylinder heads.  Sending units and OEM electric gauges can provide incorrect readings, especially on older vehicles.