RE: Club Enya
I owned my last Enya .29 that came new with both cylinder heads in 66-67. There is a way to identify them, but it evades me at the moment. I'll keep thinking about it and sooner or later it should come floating to the surface.
Being a young'un with only four-stroke hot rod (real automobile) experience before that day (ran all my two-stroke glow engines dead stock), I immediately grabbed the high compression head, mounted it to the engine and then bought a gallon of Fox Missile Mist fuel and proceded to fly the dickens out of it. Oh, that poor engine!!!
To add insult to injury, I didn't have a 9x6 or a 10x4-5 prop, so I used the same 10x6 prop that I ran on my .35 engines. This was in the desert of Luke AFB, not far from Phoenix, AZ. I don't think I could have treated that engine any worse than I did, had I originally wished to do everything to destroy it, other than throw sand in the intake or deliberately smash it into the ground. And yet, the engine improved in its running as time passed and it ran great without a single problem, or needing of a new part. Later, when I read more about how to break-in engines properly and how to optimize them, I realized just how great an Enya engine truly was to tolerate what I had done to it and still turn out great.
I'm sure the answer will emerge. Or, as you sort of suggested, you could just swap heads and check the compression that way.
Ed Cregger