There's other issues at hand that saramos pointed out. I use a Venom temp gauge with the sensor mounted directly under the top head fin on the back of the case of my helicopter engines. The advantage to this is the Venom reads the highest temp attained in flight. This often varies by 15 or more degrees from what is showing up by the time you idle it down to land, shut the motor off and spool down the blades and take a reading with a temp gun. Also the case acts like a heat sink and pulls the head down and away from the head after a short time so after the initial cool down you can watch the temp climb back up but I like the max temp while loading the engine rather than the temp taken after its slowed down, landed and checked.