Hello; I took my IR heat sensing gun to the field for two weeks and took readings of all the engines that flew for thoise two days, mostly 4 strokes. There were 3 os 70 surp;s there both days, one was 178 degrees, one was 155, the other was 225, The first one definately sounded better, but all thre of them ran fine with no dead stix. Each of them was on a GB Protoge, the hottest one had a little more vertical, and the coldest one made more smoke. The three guys tried precision airobatics, so it was easy to see the differences. Other Saitos at teh field that day were all near 180 degrees. A few two strokes I measured went from 255 down to 130 degrees. All were measured at the glo plug boss. I try to tune my 4 strokes for 175-180.