The only prop planes I got to fly on were military types and they were probably turbo-props by that time. I was on the Hercules, Caribou and Provider. Those were load enough. Seen film of B-17's starting up,impressive.
Howdy, SAM,
You got me thinking about the Caribou, I recollected radials. Google reports Pratt Twin Wasps at 1450 hp. - Liberator engines. Well, sort of grandchildren of Liberator engines! A bunch of the Canada DeHaviland machines are still in service, using turbines, Pratt PT-6s I bet.
Google says the Provider, C-123, had two Pratt R-2800s of 2,500 hp apiece. Big airplane, 80 feet long, 110 foot wingspan, could take off carrying it's own weight of 15 tons. These R-2800s were close descendents of the engines in the F4-U, P-47, and DC-6. I think they were put in early C-119s and Constellations.