Hi Tukkus,

Your question about excess heat during break in is a good one. Bottom line though, is that breaking an engine in on a test stand is a very controlled situation compared to that of taking a new engine up in a plane. Only on the test stand can you ensure that the engine will not be leaning out at any time and causing a very hot run. Experience will bear this out for you.

Also, on the test stand, run a prop that is slightly smaller in diameter, but slightly higher in pitch if you have any concerns about cooling. This doesn't seem to be usually necessary though, because guarding against an overly lean run is the main goal.

Ernie