Hi everyone,

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.

Mine runs right at 3/4's of the gauge which is exactly my thermostat setting (185)

I thought the 3/4 line would be about 212 (each division about 37.5 degrees), is that correct? Or is it non-linear?

There was a discussion here a ways back about what the lines on the OEM guage represented and I remember that the consensus lined up exactly with what my guage reads and what my T-stat is set at.

Thanks for the reply, I can't seem to find that post but I'll keep searching. I just want to know when to get nervous about the gauge and why it reads higher with the car running vs off, both at 185.

Yep - I went looking for it also and did not find it. The one I did find was somebody who wanted to "correct" his reading because he was at the 3/4 mark at 185 degrees.

On the ones I did find, there was a lot of discussion about being OK until about 200 - 210 degrees.

Hey guys....was reading the posts on the temp gauge and wanted to ask a question. I'm going to reconnect the Rally gauges in my '68 but am curious about what the different "tick" mark s mean in degrees as I've never seen anything that addresses it If the dial range is from 100 to 250 degrees with 3 tick marks in between, does that mean that each is 37 1/2 degrees, or were they calibrated for the standard 190 degree thermostat to read at some particular place on the gauge (maybe half way)? I'm running a 180 degree thermostat and don't know where is should really indicate.