What would be a better engine for a speed plane... a norvel ame .061 or the norvel .074 with perhaps a tuned pipe? I like the .061 but I really like the bolt on muffler for the .074 which would make it easy to build a pipe for. What do ya think?

I've managed to make an exhaust header for the .061, both side exhaust and rear exhaust allowing a bolt on set up. Both configurations respond well to a tuned pipe. I gain 3K on a 6 X 3 and 25% fuel using a CS (China Sang) pipe.

I've no doubt that the .074 will respond to a pipe as well, and the plus is that the bolt on feature is ready to go. I've adapted the muffler to use a long piece of Flyquiet tubing on my .074s and with a baffle in just the right place I gain at least 500 rpm. The engine is quieter and the plane is cleaner as a bonus.

I suppose all you need to do is size the plane according to the size of motor. All things considered though, the .074 looks like your best bet.

Good info thanks, where do you get a CS pipe? I did not know people actually made tuned pipes for these small engines. Could I get more speed out of the .074 then the .061 do you think?

Do a search on Google for James Zhou. Third or forth down, you will see a link with whizzz in the web address. Link on that and have a look.

I bought my pipes two years ago. Mr. Zhou, though, is hard to get ahold of. I don't know what his status is these days, his website hasn't been updated for a while.

The .074 appears to be as powerful as the .061 size for size. Speed depends on model size, weight, etc. Say you built a plane with 200 squares and got it going this fast on an .061 with a 6 X 3 prop. Then you stuck on a 6 X 4. You'd probably go faster, but your acceleration would suffer. Say you went to a 6 X 6 or a 7 X 4. Now, you'd bog down the engine and you'd likely go slower. HOWEVER, Same plane, install the .074 and stick on a 7 X 4. Obviously, you'd now go faster.

Also, this depends on the design. Swept, highly tapered wings would be faster than constant chord, straight. A delta would be even faster.