Present position of the piston engine; it still powers all operational commercial transports and all production types of heavy military bombers. The Wasp Major, a 28 cylinder engine of 3500 h.p. is currently used in many ships, ranging from the single engine Martin Mauler to the six engine B-36 Bomber. The process of development of large aircraft engines and some remarks on experimental methods. A short description of the Wasp Major and details of several research projects which were undertaken to improve the durability and reliability of the engine. The disposal of waste heat and the difficulties it causes. The need for improved oils and the effect of fuel quality.