Chrysler A57 multibank
Created in 1941 as America entered World War II, the A57 Multibank engine was born out of the necessity for a rear-mount tank engine to be developed and produced, in the shortest time possible for use in the M3A4 and M4A4 Sherman tanks.
In order to re-use existing tooling, five Chrysler 4.12 litre L-head inline six cylinder engines where place around a central crank, producing a unique 30 cylinder 21 litre engine in a relatively compact (albeit heavy) package.