Corvair engines swapped into Volkswagens

Initially, the cooling fans were designed with a twist to the vanes, so that they were only efficient when rotating in the correct direction. Early on, however, the vanes on the fan became vertical and radial, so that the fan functioned identically in either rotation. Whatever the reason for this change, one effect was that the engine could easily be configured to run in the direction opposite from stock. This proved useful for those who swapped the engine into Volkswagen Beetles and dune buggies, since the Corvair engine's normal direction of rotation was opposite to that of the Volkswagen (and most other automobiles). Otherwise, the ring gear of the Volkswagen differential had to be flipped over by 180 degrees to allow the transmission's forward and reverse directions to be correct.

This swap was fairly common at the time, with the Corvair engine serving to give a power boost to Volkswagen Beetles, dune buggies, and Karmann Ghias. Excessively vigorous use of first gear would break the transaxle (the prudent driver would avoid first gear altogether), and the engine cover of the Karmann Ghia would not close completely with a Corvair engine in place, but otherwise the swap was relatively problem free, as such things go.