Well my bad! I thought the picture was of your engines. Your engine is even more interesting. It's definitely not a Formula 1 engine, and I've used up a lot of computer "type" guessing what you have. I think it's a sport version, based on the FAI crankcase. The reason I think that it is related to the FAI engine is because of the extra set of mounting lugs. It should be a blast of fun, because it will go like heck, and still idle. Two years ago Dave Shadel modified an OS 60 carburetor for an old short stroke Nelson Quickie 500 engine for me. I used it at Vic Welland's Carolina Speed Rally in Hudson, NC. It broke 150 mph without a lot of preliminary work. It would be similar to your engine, except that it is side exhaust. Neat! Greg