RE: Preliminary TT Pro .61 Readings
I know this post is old...
Tried the APC 13X7 on the engine yesterday. Used a plug of unknown type. Might be a Thunderbolt.
I tached it at 10500 RPM with my pitts muffler and ~10% fuel (the fuel is old so I don't really know for sure).
Whew man! That thing runs like a raped ape!