Anyone familiar with this engine? I'm going to mount it on a scratchbuilt profile plane. It has a single ring. It weighs a ton (11 oz.). Will it be happy on a 5% nitro, 30/70 castor/synthetic (17% total) blend? Any prop suggestions?

Hi Frank
It is hard to tell from the one side pic, but it looks like a FOX 50
I would run at least 20% oil in it for CL, maybe even 22%

Randy

That's a wart /bump case from the 70's. I flew a few of them ,RC only, and can say that they definitely like nitro, 15% at the least. I  Used 11 inch props on them. They are also not slow running and I don't know if they would be acceptable for U/C other then sport flying. Quality of those engines was all over the place, fits were in some cases enough to give you 'fits'. That said someone will probably jump in to give more info, or have a different perspective on them.
dennis