This is the original engine designed by the fledgling Pratt and Whitney Aircraft Company in the USA. Design work started in August 1925 with the first engine producing over 400 horsepower. From this engine the design was scaled down to produce the Wasp Junior (R-985) and scaled up to produce the Twin Wasp (R-1830), Double Wasp (R-2800) and the giant Wasp Major (R-4360).
The R-1340 made significant advances in the area of power-to-weight ratio, due in part to the two-piece forged aluminum crankcase, an uncommon feature at the time. The forging process offered far superior mechanical properties and consistency compared to a casting. Other aspects of the design were a one-piece master rod riding on a two-piece crankshaft supported on two roller bearings. The master rod bearing was silver-lead-indium. Supercharging was provided by a single-stage, single-speed unit with updraft induction, and the blower ratio was typically 10: 1.
This engine powered Amelia Earhart’s Lockheed 10, the Noorduyn Norseman, de Havilland Otter, North American T-6 (Harvard), Sikorsky S-55 helicopter and the Grumman Mallard amphibian. Because of the large demand for this engine, Jacobs, Pratt & Whitney Canada, Continental, and Commonwealth Aircraft (Australia) also built them under license. Production of the engine continued until 1960. From 1925 to 1960 some 35,000 of these engines were built.