Sounds like it's simply time for an overhaul. But instead of getting Wasp replacement parts, consider getting a piston/cylinder set from LiteMachines. They're made by Norvel and will drop into your Wasp with no problems. The good thing is that one, they're still available and two, the extreme tightness the Revlite engines are famous for has been reduced considerably with the latest run for LiteMachines. No 100 flips or heat gun required. Just your usual one tank's worth of break-in and go fly.

A new engine from LM gave me 19.9K on a 6 X 3 Grish prop and 25% Cool Power fuel.

That can be seen here.

http://www.youtube.com/watch?v=-h76s_N8WPs

It would be interesting to see what a Wasp hybrid would do.