The most common windmill for the DC-3 / C-47 was this Pratt & Whitney R-1830 type piston engine
Its 14 cylinders stand in 2 rows of 7 around a central crank case, hence the name Radial or Round aero engine
The denomination R-1830 of the type stands for Radial with 1830 cubic inches of displacement (nearly 30 liters)
Divided over 14 cylinders, that brings more than 2 liters per cylinder, yielding massive pistons when compared to automotive standards.
A big V-8 automotive block of 5,0- 5, 5 liters has some 600-700 cc per cylinder max., their pistons are displacing less than one third in cc compared to the P & W aero engine.
This P & W cranked out a max of 1200 HP at take off on sea level for a short burst of a full throttle during the take off run in order to get airborne as quickly as possible.
This full throttle run was only allowed for a very short period, normally some 60 seconds, after which the aircraft was supposed to be flying at such altitude that it could safely throttle down to lower revs for sparing the engine against thermal and mechanical over stress.
This P&W engine was a most reliable but intricate machine with thousands of moving parts as rods, 14 pistons, ball bearings, 28 valves, rocker arms, valve springs, pumps, plus the hydraulic lines, electric wiring, double ignition system, the carburetor etc. A whole lot of Shaking was going on during operations, due to engine vibrations, wind load and gusts, flutter and turbulence, all of them bringing that engine under extra pressure. But they could safely run for 800-1200 hours between total overhauls