The 3W-35 is a great running engine. Since it is an older technology 3W, it does not put out the power of the newer engines but it starts easy and runs great. It also seems to have a low vibration level. Depending on the condition of the engine, you should get between 6300-6700 rpm with a 20 x 10 prop. Full power gas consumption is 1.25 oz fuel per min. Even though I have several of the current 3W engines of that class, I keep using the 35 on test airplanes due to its reliable running and good power. For one season, my 3W-35 flew a 36 lb research plane with a wing loading of 55 oz/sq ft in vertical sampling profiles from ground level to 3500 ft on numerous flights without missing a beat.

If you can find a pitts style muffler, the rpms will improve 2-300 over the banjo style muffler.

I hope this helps

Elson