"Shooting the block"

[camsna]

So. I'd like to make sure that my temp gauge is giving accurate information to me, because it's reading awfully hot. To make sure that it's properly calibrated, I need to take the temperature myself and compare the known temp with the temp gauge's reading. It was recommended that I "shoot the block."

I got a hold of an IR thermometer, but need help aiming it. I check the temp at the sender and on one side of it (on the big, brass bolt) I shoot 15ºC higher than the other side of it. The block, as you can imagine, gives me pretty wildly different temperature readings - from about 75º to about 110º.

So what's the area I'm interested in? Where's the place whose temperature reading that I can trust?

¡Gracias!