I have a mild 454 that was running 180-190 in the summer, but now that the weather is in the 50-60's, it doesn't even move the mechanical guage. The thermostat is 185 and was working last time I checked. What's the best way to correlate the guage to engine temp? If I get an IR gun, where should I point it at, the radiator, or the engine? And what part of the radiator or engine? Is there a simpler way of doing it?

Thanks for any advice.

thermostat housing should give a correct reading of engine coolant temps.