Editing Allison V-1710 (section)

===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 [[Long block|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.<ref>Whitney 1998, p 49</ref>

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 F-82 Twin Mustang|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.<ref>[http://miravim.org/avimlibrary/Manuals/Powerplant%20Manuals/Other%20Engines/Allison%20Handbook%20of%20Operation%20and%20Maintenance%20for%20Allison%20V-1710%20F%20Type%20Engine,%20ALD-3-F2%203rd.%20Edition%20April%201,%201943.pdf]{{Dead link|date=September 2019|bot=InternetArchiveBot|fix-attempted=yes}}</ref>  The ability to reverse the direction of rotation with a minimum of extra parts to achieve the task allowed the use of either a [[Pusher configuration|"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 {{convert|8000|to|26000|ft|m}}.