A customer brought me a 1970 Three Hundred with a recently rebuilt 440 engine that he thinks is running hot. Aftermarket digital temp gauge with a sending unit mounted in the factory location shows 235 to as much as 250 degrees. Installed a mechanical gauge in the plug on top of the water pump housing and it also shows the same reading.
My infra red temp gauge shows 185-205 at the sending unit location. It also shows top hose in the same range and lower rad hose about 40 degrees cooler. You can watch the temp rise and fall with the opening and closing of the thermostat which to me shows that it is not that hot or the thermostat would stay open.
Engine shows no signs of being that hot, starts easily when warm without touching gas pedal and idles perfectly, no ticking or smells like a warm engine, etc. No excessive underhood heat when you open the hood either.
Replaced water pump just to be safe, thought maybe impellers were slipping or bad in some way.
So, is it really that hot? and if not, why does the gauge read that high?
Any help or suggestions would be appreciated. I am out of answers.