I have a 1970 455 in my firebird and the temp gauge reads slightly over the 3/4 line. Last night I took a thermal gun and read the sensor and thermostat gooseneck and it's reading between 185-190. I read online that there are quite a few brands that fit our cars but they all give off different readings and not really meant for us but do fit on the intake (as they all have different temp vs resistance curve), for example the standard motor products TS-6 or Wells TU-5 or original GM #1513321, check this thread click here
So I turned the car off and read the thermostat with the thermal gun still at 185, take a look at the gauge and it's reading right! It almost looked like the gauge is reading higher when the car is running but with the ignition on but car off, the gauge reads right. So I'm not sure if my speculation that I should use a different sensor is correct. Does anyone have any input or experience on this, I would greatly appreciate it.
