Our last AKEOTD was a Chrysler-built tank powerplant, and you'd think it would be impossible to surpass a five-bank, 30-cylinder monster… but the IV-2220 airplane engine does just that. It's the very first Chrysler Hemi!

The "2220" stands for its displacement in cubic inches (actually, it was 2,219.35 CI, or just over 36 liters). That's right, an engine with well over a cubic foot of displacement. Oh, but it gets even better! More than ten feet in length, hemispherical heads, aluminum block, single overhead cam, inverted-V configuration, and the power was sent to the propeller reduction gear via the middle of the crankshaft (technically, the IV-2220 was two V8s joined in the middle, with an output shaft extending to the propeller beneath the crankshaft). It was developed for installation in the P-47 Thunderbolt during World War II (the P-47, as you may recall, had a godawful complicated remote-turbocharger setup), as an alternative to the P-47s standard Pratt & Whitney radial, and made an impressive 2,500 horsepower. By the time the IV-2220 was ready, however, the war was just about over and jet engines were the flashy new trend for aircraft power. All that effort wasn't wasted, though, because Chrysler had learned a great deal about hemispherical head design, and you know the rest.
[Allpar, Wikipedia]