Pratt & Whitney Twin Wasp D Series engines operators handbook (PDF)
Derived as a modest development of the Twin Wasp R-1830, the R-2000 was designed specifically for the Douglas DC-4 commercial airliner, allowing use of lower octane fuel than generally used by the military. It was also used on the Air Force C-54 and Navy R5D (military versions of the DC-4); the Vought XF5U-1; Chase YC-122; and Cancargo CBY-3, Aviation Traders Carvair, the Douglas Super DC-3 and the De Havilland DHC-4 Caribou.
The R-2000 focus was on reducing the manufacturing costs and fuel requirements. The bore was increased to 5.75 in (146 mm), while it still retained the 5.5 in (140 mm) stroke. This brought displacement up to 2,000 in3 (32.8 l). There were a number of detail changes from the R-1830, such as front-mounted instead of rear-mounted magnetos (as with the larger, and earlier Double Wasp), plain bearings for the crankshaft rather than roller bearings, and 87 octane fuel (specified because there were fears wartime supplies of 100 octane might fall short, but those fears were groundless). The R-2000 produced 1,300 hp @ 2,700 rpm with 87 octane, 1,350 hp with 100 octane and 1,450 hp @ 2,800 rpm with 100/130-grade fuel.
The engine first ran on 21 May 1940 and was first delivered on 7 Aug 1941. Between 1941 and 1949, Pratt & Whitney, and the General Motors Buick Division under license, built 12,966 Twin Wasp D engines.
PDF to download - 181 pages - in english