I think you hit the nail on the (red ) head Ed...
When my nephew and I were first learning to fly C/L with "big" engines, (we were about 13 ) we had my brother's McCoy Red Head .35 in a (I think it was a Scientific?) P-40...
We used to peak it right out, and wonder why it would only go for about 15-20 laps before over-heating and quit.

We finally got some advice from another guy who told us about the 4 cycle to 2 cycle "break"...
Unfortunately, it was too late for that red head... cuz we over-heated it a few too many times...

I got my own McCoy shortly after that...one of the bulky, square cased "Series 21" .29's and put it in a CG Shoestring Stunter.

It has maybe a half a gallon thru it and the rod is real sloppy loose

I digressed a bit for awhile there...memories, ya know?

Didn't do much to answer the question...sorry