meowy84,

This is an interesting question. It seems some engines run cooler than others. I know the exhaust gas temp of a Enya 155 is hotter than any four stroke I have ever run. Hot enough to melt Teflon. The engine was adjusted 200 rpm down from peak and had plenty of air over the cylinder and good flow of exit air about 3x more outlet than inlet.

The only advise I would have would be to get an onboard temp meter like an Eagletree system and fly the engine without cowl and check the temps and then cowl and duct the engine to get about the same temps.