R-2600 Twin Cyclone, with 14 cylinders

Here powering the North American B-25J Mitchell "Tondelayo" from the Collings Foundation.

In 1935, Curtiss-Wright began work on a more powerful version of their successful R-1820 Cyclone 9. The result was the R-2600 Twin Cyclone, with 14 cylinders arranged in two rows. The 1,600 hp R-2600-3 was originally intended for the C-46 Commando and was fitted to the CW-20A prototype, but a running change[clarification needed] led to the adoption of the 2,000 hp Pratt & Whitney R-2800 in its place. The Twin Cyclone engine went on to power several key World War II production aircraft including the B-25 Mitchell.