I have a 3W 100 (about 4 years old). On the test stand last weekend, no baffles, with 27x12 prop, both cylinders were around 200 degrees F. it varies somewhat depending upon where you point the temp sensor. I was pointing from the rear with the engine running, and pointed at the cylinder near the spark plug. also about halfway down the fins. After shutting off the engine, I also shot it from the front. Outside air was about 60 degrees. I have had the temp sensor for about a year and play around with it from time to time. Sometimes after landing, and idling back down the runway, the temps are about 180. If I get it too lean, it will go over 220. sometimes one cylinder is 20 degrees cooler than the other. never more than 20 degrees. I have read of other engines that varied by a lot more. hope this helps.