The two fastest airplanes in the history of the sport represent two vastly different approaches to the same problem. The P-51 is a smaller, lighter airframe, with a V-12 water-cooled Merlin race engine running at above 120 inches of manifold pressure and putting out something in excess of 3000hp through a reduction gearbox to a four-blade propeller. The Bearcat has an air cooled R-3350 radial of twice the displacement producing over 4000hp, with the big 3-blade prop bolted directly to the crankshaft. The big radial won't handle much more than 70 or 80 inches of manifold pressure.