Editing Allison Engine Company (section)

===Hyper engine===
In the late 1920s the [[United States Army]] funded the development of a series of high-power engines, as part of its [[hyper engine]] series, which it intended to produce on [[Continental Motors Company|Continental Motors]]' production lines. Allison's manager, Norman Gilman, decided to experiment with his own high-power cylinder design. Allison's engine became Manufacturer Serial No. 1, AAC S/N 25-521. It was the X-4520, a 24-cylinder air-cooled 4-bank “X” configured engine designed by the Army Air Corps and built by the Allison Engineering Company in 1925. The result was presented to the Army in 1928, which turned down the development proposal.<ref name="Leonard" />