Chrysler A57 multibank

The Chrysler A57 Multibank is a 30-cylinder 1,253 cu in (20.5 L) engine that was created in 1941 as America entered World War II. It was born out of the necessity for a rear-mounted tank engine to be developed and produced in the shortest time possible for use in the M3A4 Lee medium tank and its successor M4A4 Sherman medium tank. Each had lengthened hulls to accommodate the A57.

Chrysler A57 Multibank
Overview
Manufacturer	Chrysler
Layout
Configuration	Multibank (5-bank W30)
Displacement	1,253 cu in (20.5 L)
Cylinder bore	3.4375 in (87 mm)
Piston stroke	4.5 in (114 mm)
Compression ratio	6.2:1
Combustion
Fuel system	Naturally aspirated (i.e., unsupercharged), Carter TD-1 carburetors[1]
Fuel type	Gasoline
Cooling system	Liquid
Output
Power output	370 hp (276 kW) @ 2400 rpm

In order to use existing tooling, five Chrysler 250.6 cu in (4.1 L) (bore 3.4375 in or 87 mm, stroke 4.5 in or 114 mm)[1] L-head inline six cylinder engines were arranged around a central shaft, producing a unique 30-cylinder 21-litre (1,253 cu in)[1] engine in a relatively compact but heavy package. The crankshafts were fitted with gears, which drove a sun gear arrangement.[2] With iron block and head,[1] it featured Carter TD-1 carburetors[1] and 6.2:1 compression ratio,[1] for an output of 370 hp (280 kW) at 2400 rpm.[1] It necessitated a longer hull (same as the M4A6),[3] becoming the M4A4;[3] most of these were supplied to Allied countries under Lend-Lease.[3]

In the February 1944 issue of the magazine Popular Science, an advertisement by Chrysler claimed the A57 could still move the tank it was fitted in even if 12 out of its 30 cylinders were knocked out.[4]

A total of 109 Lees and 7,499 Shermans were fitted with the A57. The M4A4 was largely supplied to the British, the US preferring the M4A3 with the more conventional Ford GAA V8 engine, and restricting their M4A4s to overseas use.[5]