An R-250 or R-350 sounds cool! You’d likely have to turn the cylinders 90° to the airflow from how Continental did it but come to think of it that may be the way air is supposed to pass over the fins anyways.How 'bout a 5 or 7 cylinder radial using O-200 cylinders? Paging Pete Plumb...
At 4500 rpm? It would need a PSRU, which would dramatically increase your torque, unless you’re putting it on something really tiny, like a later Davis single place.The VM R5-420 radial , is 420cc , but only puts out 25 hp ; i
would have thought it could have put out more hp ?
Hello Crusty,Building one requires a LOT of machining. If someone is VERY serious about building one, I have Jack’s email address that I can PM, but he’s too busy to interact with the merely curious and tire kickers. He sells plans only now...though I’m not sure if he’s still doing that. They were around $200. If you want to use cylinders other than VW, I advise you to study up on radial engine design & theory and design & build one using those cylinders instead of trying to adapt Jack’s designs. I, too, pondered designing & building a 75hp 3-cylinder radial, using 0-200 pistons & cylinders, as a substitute for a Lawrance L-3, but life kept getting in the way and I moved on.