For this week’s “Case of the Mondays,” we thought that this is a fun little nugget of American World War II history you hard core engine lovers would get a kick out of. Everybody knows that when the war came onto American soil, Detroit’s Big Three quickly shut down automotive production and lent their resources and talents to building one of the largest militaries in the world. Created in 1941 as America entered in the war and born out of the Army’s need for a rear-mounted tank engine in the shortest time possible for use in M4A4 Medium tank, Chrysler developed and produced the A57 Multibank engine.

Image: Wikipedia

While using existing tooling to keep development costs low, five Chrysler 250ci (4.12 liter) L-Head inline six cylinder engines were arranged around a central shaft, creating this unique 30-cylinder, 21-liter radial-style engine. This relatively compact (but exceptionally heavy) powerplant featured its many crankshafts fitted with gears that drove a “sun gear” arrangement. Each straight-six was comprised of an iron block and head, and featured its own Carter TD-1 carburetor^. Pressing a 6.2:1 compression ratio, the Multibank produced roughly 370hp at 2400 rpm. Its size and heft necessitated a longer hull, so the M4A6 chassis was modified, becoming the M4A4.

In February 1944, Chrysler published an advertisement in Popular Science claiming that the A57 could still propel the M4A4 tank even if 12 out of the 30 cylinders were disabled. The M4A4 was largely supplied to the British, while the US preferred the M4A3 with its more conventional V8 engine.