Has anyone with a CHT gauge used a thermometer gun to check the accuracy of it? I was just pointing mine at the base of the spark plug on #3 and was only getting upper 200°. But it may have not been totally warmed up yet and it was just idling.

I would trust the CHT (if its a good one) before I trusted the IR gun.

There is not any good way to get the IR gun to measure the head where the ring terminal sits.

Under #3 is the hottest part of the non-exhaust tract for the motor (in theory). So any other place you take a head temp reading (including on the top of the #3 plug) will be cooler - probably significantly cooler.

Zach

Try to remove it from the car and check by applying some heat carefully with a small torch or lighter.

Just make sure there are no gas fumes.

A non-contact thermometer is a useful tool. Great for checking tires and bearings when towing a load

Great idea, also when you’ve put beers in the fridge recently and checking if there cold enough

Cheap IR thermometers make some assumptions when calculating temperature that you can't change (emissivity and a few other things). It'd be interesting to see what you read if you painted the end or your spark plug vs. shiney metal since that would bring its optical charactertics closer to most of the assumptions.