The Orr Tornado 65 was a 0.647 cuin (10.60 cc) spark ignition racing engine designed by Wilfred "Fred" Gibbs Orr and manufactured between 1946 and 1948 by Modern Engineering Products Co. of Niles, Michigan. The venture was financed by Fred Orr's father, and the engines were marketed from Orr Senior's address in Lansing, Michigan.

Orr's original design of late 1945 was a crankshaft front rotary valve (FRV) .604 cuin. (9.90 cc) twin ball race spark ignition unit. This ran OK but didn't perform up to Fred Orr's expectations. The subsequent disc rear rotary valve (RRV) twin ball-race variant was designed in consultation with Merle Dreher, the chief engineer at Modern Engineering in Niles.

At only 13.5 ounces (383 gm), the Orr 65 was one of the lightest full-blown racing engines of its displacement ever offered. It was also notable for having a ball-race bearing for the rotary disc. An output of 0.85 BHP @ 13,500 rpm was claimed by the manufacturers. Based on the engine's specification, this claim appears to be entirely credible.

The engine was mainly distributed in and around its native Michigan. It did achieve some competition success in that area, but sales overall were insufficiently brisk to encourage further development.

A full review and test of the Orr 65 appears elsewhere on this website.