Weird Warrior: Chrysler’s A57 30-Cylinder Tank Engine

Necessity is the mother of invention, especially in wartime. Here’s one of the most unusual powerplants ever produced in the Motor City: the 30-cylinder Chrysler A57 tank engine of World War II. Let’s take a closer look. 



Despite some shortcomings, the Sherman M4 tank was a valuable tool for the Allies in World War II, and it was produced in vast numbers—nearly 50,000 units. One of the challenges was in building suitable engines for the 40-ton tank in sufficient numbers. The array of powerplants included converted aircraft radials in both gasoline and diesel form, twin GM 6-71 diesels, and a giant 1100 CID Ford V8. But easily the most unusual engine of the bunch was the 30-cylinder A57 Multibank engine developed in 1941. Essentially, five Chrysler inline sixes were lashed together in a star pattern to form a sort of quasi-radial.


In a nutshell, these schematic views show how the A57 was laid out: five standard Chrysler passenger car engines were configured in a circular pattern, forming one dense and heavy unit. Five helical gears at the ends of the crankshafts drove a sixth gear and an output shaft.


This view of the Multibank engine on its assembly fixture clearly illustrates the clever setup devised by Chrysler lead engineer Harry Woolson and famed Chrysler engine wizard Mel Carpentier. Each of the five L-head inline sixes featured a bore of 3.4375 inches and a stroke of 4.5 inches, displacing 250.6 cubic inches. Total displacement was 1253 cubic inches (21 liters) and the total weight with accessories was nearly 5,250 lbs. Various output figures have been quoted, from 370 hp to 445 hp at 2,400 rpm, and with a very ordinary 6.2:1 compression ratio the engine could run on regular gasoline.


This rear view of a Multibank engine shows the enormous shaft-driven, cast-aluminum cooling fan along with the housing and radiator. Several carburetor and intake systems were tried in an effort to improve fuel distribution. The beautifully restored example shown here was on display at the Walter P. Chrysler Museum for many years, giving many visitors their only opportunity to see the unusual engine. Unfortunately, the museum is now permanently closed.

Between July 1942 and November 1943, some 7,499 Sherman M4 tanks with A57 Multibank engines were built by Chrysler at the Detroit Tank Arsenal in Warren, Michigan. Known as the M4A4, the A57-equipped Sherman (below) required a lengthened hull to accommodate the 30-cylinder engine, which was mounted at the rear with the fan facing aft. (Around 100 M3A4 Lee tanks, the Sheman’s predecessor, were also equipped with the A57.) Most of the M4A4 tanks produced were supplied to the British military under Lend-Lease, and dozens, maybe more, still exist in museums and collections around the world.


13 thoughts on “Weird Warrior: Chrysler’s A57 30-Cylinder Tank Engine

  1. Whoa-Ho, mama, that’s what I’m talking about!!! This thing is awesome, not unlike the Napier-Deltic diesel. I’m just flabbergasted at what was done to achieve necessary results. I can just see the test session, hmm, not quite, let’s add a couple more motors. A modern diesel puts out 3 times the hp in a third of the space. None the less, I read, the Sherman tank was a sight for battle weary eyes. Progress would be made with a row of Sherman tanks in front of them. While I’m sure most of the tanks were de-commissioned and cut up, I wonder if any of these engines survived. Would look really cool in a rat-rod. Thanks for the history lesson.

  2. I photographed many of the Detroit Section SAE events from the late 80’s until the early 2000’s and saw one of these engines at the then newly opened Walter P. Chrysler Museum. It was awesome and really an engineering marvel. One of my fellow SAE members, a Chrysler engineer whose name i don’t recall, was tasked with finding this engine and getting it restored to museum quality.

  3. Even though we were at war development of new engines and equipment went on non-stop. Essentially (5) 251 Chrysler sixes bundled together. Sure wouldn’t have to worry about traction. That combination would’ve weighed almost as much as the (2) Detroit 6-71’s. i’m not sure how much that monster Ford V-8 weighed. I’d like to see one of these Chrysler units….

  4. As I remember, the Chrysler Museum also had photos of this engine installed in a war bird. Whatever the air frame, it was um……heavy.

    • At 5,200 lbs and 445 hp, it’s fairly safe to say that this engine never flew. (A Pratt & Whitney R-2800 occupied about the same space, weighed less than half as much, and produced 5X the horsepower) You’re probably thinking of the Chrysler XIV-2220, an advanced, purpose-built engine which did fly and might have become quite successful had there been any real need for it.

  5. One of the more difficult aspects of getting this motor to run properly was metering the fuel which gave the engineering staff a good challenge. I was privileged to meet and get to know the late Burt Dickenson, one of the very talented fuel systems engineers working for Chrysler at that time. He was called upon to sort out the fuel problem that had stymied others for weeks. Burt explained how he went about the task of problem solving given the technology of the day. It took him about a week to get it figured out and the rest they say, is history.
    Chrysler has employed some of the most brilliant engineers in automotive history – Burt was one of the best.

    • Flathead engines were more compact than overheads & simpler to build & maintain.

  6. Some wild engineering there! Wonder how they came up with the idea to lash 5 engines together like that? I guess one thing was they were using what they had available in quanity at the time, but 5 of them? Seems like two would have the first idea, but maybe there just wasn’t enough torque and horsepower there. I would have hated to be the guy in the motorpool that had to sync the firing order and the carbs, especially the lower engines!

  7. Just think. Basically the same engine that was under the hood of my 1951 Plymouth Sedan & my 1958 Plymouth Suburban helped us win WWII. I’m bursting with pride…..

  8. Very unfortunate that the Chrysler museum has been “re-purposed”. I think it went unappreciated.

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