These engines were, in fact, geared down, as was common (if not ubiquitous) in large piston aero engines. This video shows an epicyclic reduction gear inside th

These engines were, in fact, geared down, as was common (if not ubiquitous) in large piston aero engines. This video shows an epicyclic reduction gear inside the bell-like case on the front. https://youtu.be/EyPvpdy4dgg?t=117 https://youtu.be/EyPvpdy4dgg?t=117 IIRC, piston speed was an issue in how fast these engines could run, as, for given RPM, the piston speed is proportional to the stroke. And, for reliability and the corresponding safety reasons, aero engines are more conservatively designed than most car engines.