off the front of the engine you will likely see 150 degrees C at the most. The base of the spark plug is the best location to measure temperatures short of drilling holes into the engine for thermocouples. Like Pe stated paint some flat black paint on the location and use your IR tool at the same angle, etc when you make the readings. 180 to 200 or so degrees C seems about normal for the engines with lots of cooling fins. Some of my engines that are, more or less, converted glow engines with short fins tend to run more hot though upwards of 225 degrees C or a little more even. The engines tend to run more hot on the ground in a static load situation versus when flying in the air too, where the prop unloads off the engine more.