Chevrolet Corvair Engine

The Chevrolet Corvair engine was a flat-6 (or boxer engine) piston engine used exclusively in the 1960s Chevrolet Corvair automobile. It was a highly unusual engine for General Motors: It was air-cooled, used a flat design, with aluminum heads (incorporating integral intake manifolds) and crankcase, with individual iron cylinder barrels. The heads were modeled after the standard Chevrolet overhead valve design, with large valves operated by rocker arms, actuated by pushrods run off a 9 lobe camshaft (due to the unique engine layout, exhaust lobes operated valves on *both* sides of the engine), running directly in the crankcase bore without an inserted bearing, operating hydraulic valve lifters, as used on most Chevrolet OHV engines.

The flat horizontally opposed ("flat engine") air-cooled engine design, previously used by Volkswagen and Porsche as well as Lycoming aircraft engines, offered many advantages. Unlike inline or V designs, the horizontally opposed design made the engine inherently reasonably well balanced, so that counterweights on the crankshaft were generally not necessary, reducing the weight greatly. Eliminating a water-cooling system further reduced the weight, and the use of aluminum for the heads and crankcase capitalized on this weight reduction; so that with the use of aluminum for the transaxle case, the entire engine/transaxle assembly weighed under 500 pounds (225 kilograms). In addition, the elimination of water-cooling eliminated several points of maintenance and possible failure, reducing them all to a single point; the fan belt. As with the Volkswagen and Porsche designs, the low weight and compact but wide packaging made the engine ideal for mounting in the rear of the car, eliminating the weight and space of a conventional driveshaft.

Two years after its 1960 debut, the Corvair engine gained another unusual attribute: it was the second production engine ever to be equipped from the factory with a turbocharger, released shortly after the Oldsmobile Jetfire V8.

Given the engine's air-cooling, aircraft amateur builders and small volume engine builders very quickly began a cottage industry of modifying Corvair engines for aircraft use, which continues to this day.

The Corvair engine also became a favorite for installation into modified Volkswagens and Porsches, as well as dune buggies and homemade sports and race cars.