R-1300-2 A direct drive version of the R-1300-1. It had a 0.5625:1 reduction drive. Both used the PD9F1 carburetor.[2] R-1300-3 Derated to 690.3 hp (515 kW), uses forced-air cooling fan and uses a PD9G1 carburetor.[2] R-1300-4 Similar to the R-1300-1, uses some different accessory components.[2] R-1300-CB7A1 With reduction gear for use on fixed wing aircraft.