For this project I was able to locate and purchase a 1941 Kinner 5-Cylinder radial engine out of an old Navy Warbird known as the Ryan PT-22 Recruit.
Shown here on my test stand (configured to run with electronic ignition and fuel injection under MegaSquirt V3), this Kinner R-55 is a 4-cycle, 5-cylinder, direct drive radial engine that saw commercial use as well as military duty (as the R-540-1 and R-540-3 models) through the 1930s and 1940s.
Stock specs: 160 hp continuous at 1975 rpm, burns 73 octane gas, has a 5.25:1 Compression ratio, 5 inch bore, with a 5.5 inch stroke, displaces 540 cubic inches, measures 45 inches in diameter and weighs 338 lbs.
This Kinner radial engine has a couple very unusual features; there is no lube oil to the heads. Grease fittings provide lubrication to the rocker arms and push rods. And instead of a 'cam ring' (like almost all other radial engines of this period) each cylinder has its own cam shaft.
I have Kinner radial engine parts for sale.