format, for a displacement of , with a compression ratio of 6.65:1. The valvetrain has a single overhead camshaft per bank of cylinders and four valves per cylinder. Versatility and reversibility of rotation The engine design benefited from the General Motors philosophy of built-in production and installation versatility, embracing a philosophy of modular design for aviation powerplants. The engine was constructed around a basic power section, from which different installation requirements could be met by fitting the appropriate accessories section at the rear, and an appropriate power output drive at the front. A turbo-supercharger could be used, if desired. The P-39, P-63, and Douglas XB-42 Mixmaster used V-1710-Es, exchanging the integral reduction gear for an extension shaft driving a remotely located reduction gear and propeller. Aircraft such as the P-38, P-40, P-51A, and North American P-82E used close-coupled propeller reduction gears, a feature of the V-1710-F series. The accessory end had a one- or two-speed engine-driven supercharger that might have a second stage with or without an intercooler, the ignition magnetos and the customary assortment of oil and fuel pumps, all dictated by the application requirements. The front of the engine could have one of a number of different output drives. The drive might be a "long-nose" or close coupled propeller reduction gear, an extension drive to a remote gearbox, or a gearbox that could drive two wing-mounted propellers from a fuselage-mounted engine. Another key feature of the V-1710 design was its ability to turn the output shaft clockwise or counter-clockwise by assembling the engine with the crankshaft turned end-for-end, by installing an idler gear in the drive train to the supercharger, camshafts, and accessories, installing a starter turning the proper direction, and re-arranging the ignition wiring on the right side to accommodate a changed firing order. No change to the oil pump nor coolant pump circuits was needed. The ability to reverse the direction of rotation with a minimum of extra parts to achieve the task allowed the use of either a "tractor" or "pusher" propeller. This approach allowed easy changes of the supercharger(s) and supercharger drive-gear ratio. That gave different critical altitude (the maximum altitude at which the engine could produce full power) ratings ranging from . Supercharger The V-1710 has often been criticized for not having a "high-altitude" supercharger. The comparison is usually to the later, two-stage, versions of the Rolls-Royce Merlin 60-series engines also built by