Manufacturer Chrysler Displacement 1,253 cu in (20.5 L) Piston stroke 4.5 in (114 mm) | Configuration Multibank Cylinder bore 3.4375 in (87 mm) Compression ratio 6.2:1 | |
 | ||
Created in 1941 as America entered World War II, the A57 Multibank engine 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 both the 109 examples built of the M3A4 Medium Tank, and the 7,499 examples built of the successor M4A4 Medium tank, each of which had lengthened hulls to accommodate them.
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) L-head inline six cylinder engines were arranged around a central shaft, producing a unique 30-cylinder 21-litre (1,253 cu in) engine in a relatively compact but heavy package. The crankshafts were fitted with gears, which drove a sun gear arrangement. With iron block and head, it featured Carter TD-1 carburetors and 6.2:1 compression ratio, for an output of 470 hp (350 kW) at 2400 rpm. It necessitated a longer hull (same as the M4A6), becoming the M4A4; most of these were supplied to Allied countries under Lend-Lease.
In a February 1944 advertisement on the magazine Popular Science, Chrysler claimed the A57 could still move the tank it was fitted in even if 12 out of its 30 cylinders were knocked out.
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 from overseas use.
Museum display
The engine was preserved at the Walter P. Chrysler Museum in America and at the Imperial War Museum Duxford in the United Kingdom.