First developed in 1934, the Jacobs L-4 series engines were produced for aircraft use over the next forty years. Of simple design, the R-755-9 proved long lasting and durable, due to its relatively low horsepower/rpm ratio. Reliable under even severe training conditions, the Jacobs engine could be run up to 1,200 hours between major overhauls. The engine on display was built for a US Army Air Force contract and delivered on March 6, 1942. It was acquired in 1986 and restored by museum volunteers prior to 1997.