Hey Dave, Im having a problem getting compression out of my 63FZ. The engine was sent back to you guys late last year for service and you replaced the head/cylinder. I've just now got the engine back flying and the compression will not come up. I've probably got about 40min worth of time on the motor now. Initially the engine was run fat with a heavy smoke trail throughout the power band. Now I've started leaning it out so there is a light smoke trail though low-mid and it gets slightly richer on top. The engine runs ok but acceleration is slugish and RPMs tend to wander at high end. Does it take this long for the compression to come up or does my 63 still have issues??

Oh, I'm running an OS Type F plug and Wildcat 20/20 fuel with a APC 13x4w prop.

Check the valves. They should be at .003" for both. If it doesn't increase compression, it will need to come back. Sorry.