The Ford Motor Company has built nearly every kind of V8 engine we can imagine over the past century, but the biggest was the 1100 CID GAA tank engine of World War II. 

The GAA V8 story actually begins with a proposed Ford V12 aircraft engine (above) that was developed in the hectic days leading up to the USA’s entry into World War II. Much misinformation surrounds this engine: contrary to the campfire stories, the Ford V12 was not a copy or derivative of the Rolls-Royce Merlin engine, but an all-new design. And it was a particularly advanced one, with four valves per cylinder, double overhead camshafts, bucket-style valve followers, and an exhaust-driven turbo-supercharger. Additionally, unlike the Merlin, this engine was designed for high-volume production with a number of castings in its construction. (Ford did produce thousands of Rolls-Royce Merlin engines at its Trafford Park plant in England.)

The U.S. government declined to approve the Ford V12 for production, but not due to any particular fault of the engine, reportedly. Rather, the U.S. military planners, especially at the navy, were focused on air-cooled radials rather than liquid-cooled inline engines for aircraft use. But the Allied war effort was in desperate need of tank engines for the ground war, which was bound to be protracted and difficult, so the Ford V12 was hastily converted into a V8 (hence the 60-degree bank angle). With a bore and stroke of 5.402 inches by 6.0 inches, the V8 version displaced 1100 cubic inches (18 liters) and was nominally rated at 500 hp at 2600 rpm, with 1050 lb-ft of torque at 2200 rpm.

Ford produced the GAA and its variants (GAF, GAN, etc., and a V12, the GAC) at its Lincoln auto plant on Warren Avenue on the west side of Detroit, above. Historically, this brought the Lincoln facility full circle, if you will. Henry and Wilfred Leland had originally built the factory to produce Liberty aircraft engines for World War I.

By passenger car standards, the GAA was enormous: five feet long, four feet tall, and  almost 1,500 lbs. But it was a perfect fit in the engine bay in the rear of the Sherman M4A3 tank, below, which weighed more than 71,000 lbs, sported a 76mm gun, and carried a crew of five. Various engines were used in the Sherman, including the strange Chrysler A57 we featured here.

Produced in vast numbers, the Sherman was instrumental to the Allied war effort, especially in infantry support. The GAA-series engines were used in other U.S. military tracked vehicles as well, and all told, more than 28,000 of the monster V8s were manufactured between 1940 and 1950. Experts estimate that somewhere between 500 and 1,000 of the engines are still in existence today.