FED the Leonides Major in the Whirlwind Mk 7 & 8 had a double bank radial with 14 cylinders producing about 750 HP. In the Mk 7 it was cartridge start, the RRPM were 213, normal max manifold was 44" but up to 46" (if my memory serves me well)in the tropics. However, with a MAW of 7800 lbs it really struggled in the tropics, with 4 troops if you were lucky into a clearing. Coming out required patience and very smooth handling( + a bit of luck).