What size venture, and what is a good needle valve assembly to use in this engine also?  Thanks

'Legger,

I have a pair of pretty worn S-30s. Used them in an Umland Super Combat Streak, set up as a sport/stunt plane. It is pretty light, what with the Umland wood selection and a MonoKoted wing. The engine with the better piston-liner fit runs super steady with a classic stunt run, but not great power any more. It has a nylon .257 ID venturi with an OS needle (.135 OD) thru the hole in the case. That results in a flow area of about 0.0172 in^2. It is very happy on 10% nitro and 28% castor. I used a Jim Lee tongue muffler with 10 3/32" holes. No issues with the OS needle valve. Even the more worn engine starts cold easily and runs beautifully, but has less power. Hot starts need more technique. I've been tempted to purchase a new P/L and put it back to work....

I forget what prop I had on this combination as I pulled it out for an OS S-35 recently. But it was definitely a wood prop and probably a 9x5 or 9x6, and possibly a 10x5. I just don't remember. The plane was too slow for good line tension on 60' (it is a Flight Streak, after all) but the engine setting that made it happy just didn't pull enough prop. A thinned-down prop or a carbon prop would help unload the engine and make more of the power useful. I don't like flipping carbon props on sport planes. It was just easier to swap the engine for now.

Wish you the best with yours,

Divot McSlow

 Thanks a lot fellow's that helped a lot, now where can I get the venture "O" ring for the O S 30 venture?  In all of this the "O" ring disappeared !!!