A flat-ten engine, also known as a horizontally opposed-ten, is a ten-cylinder piston engine with five cylinders on each side of a central crankshaft.

There are no known flat-ten engines which reached production.

In the early 1960s, Chevrolet built several prototype flat-ten engines as part of an aborted program for family of Modular Engines to replace the Chevrolet Turbo-Air 6 flat-six engine.[1] This development program investigated flat engines with between two and twelve cylinders, with the flat-ten version being known as "P-10" ("pancake" engine). Although the program was initially intended to develop an engine for the 1964 Chevrolet Corvair (which is rear-engined with rear-wheel drive), the flat-ten version was fitted to an experimental 1962 Chevrolet Impala (a front-engined car which was converted to front-wheel drive).[2]


  1. ^ Niedermeyer, Paul (14 June 2017). "Engine Prototype: The Stillborn Corvair Gen2 Modular Engine – From Two to Twelve Cylinders". www.curbsideclassic.com.
  2. ^ Newell, Dave (April 1995). "Hitting on All 10". Corvair Communique. Vol. 17, no. 4. Corvair Society of America. pp. 13–16.