The only EGT indication that matters is
degrees from peak. Absolute values (
"EGT's at high temp were: 1498, 1487,1449 and 1377") are useless for tuning, and only approximate for quickly setting inflight mixture.
Jetting very rich (or very lean) does reduce CHT, but the engine is no longer making rated power. I won't say it's a wrong approach, but it does burn cubic dollars for less whoopee. I'd suggest jetting (or swapping restrictors, or pushing buttons on the SDS control head) so all cylinders fall into the 100 to 200 ROP window, and then working out the necessary cooling to enable the use of all the expensive Lycoming power.
IO-540K angle valve, on the FAA dyno at Hughes. Best power is 100 ROP. Anywhere from 50 ROP to roughly 200 ROP keeps power within 2% of maximum. At 300 ROP power is down about 5.5%.
