Obviously, the first seven words of the title (“Ford’s Aluminum DOHC 32-Valve Flat-Plane V8”) immediately evoke the thought of the Shelby GT350’s 5.2-liter Voodoo engine. However, the last three words (“From The 1940s”) might throw you for a loop. See, we’re talking about an engine from much longer ago than 2016, and a little over 3.5 times larger than the modern 8,200 rpm screamer. This behemoth is an engine that was in production almost 85 years ago, with the Second World War in full-swing in Europe. Of course, we’re talking about the Ford GAA engine.
The monster 1,110-cube (18.0-liter) V8 engine had a 60-degree bank-angle aluminum block with a 5.400-inch bore and 6.00-inch stroke, very similar to the famous Merlin engine, but ultimately with four fewer cylinders. Originally, the V12 Merlin copy was intended to be an aircraft engine. However, politics and wartime needs saw the design get cut by four cylinders and shoved into the tanks being cranked out as fast as possible in preparation for war.
Powering seven variants of the Sherman tank, the M10 tank destroyer, the M7B1 self-propelled 105mm Howitzer, and the M74 tank recovery vehicle, the GAA V8 had two additional variants. The GAN powered the T23 and M4A3E2 tanks, and the GAF powered the M26 and M26A1 Pershing tank, the T28 tank destroyer, and the M45 tank.
The GAA engine had a pair of aluminum cylinder heads with a dual overhead camshaft design and four valves per cylinder. Naturally aspirated, the Stromberg carburetors fed dull-by-todays-standards 80-octane gasoline to the monster engine — the largest gasoline-gulping V8 Ford ever built — and made 525 horsepower at 2,800 rpm and 1,050 lb-ft of torque at 2,200 rpm. The GAA engine had a compression ratio of a scant 7.5:1 with five rings on the large pistons — three for compression and two for oil control.
Even though it performed better than its contemporaries, like the Chrysler A57 Multibank we have discussed previously, eventually more power was needed, so the previously removed four cylinders were added back to the design and it was renamed the GAC engine. Making about 50 percent more power (770 horsepower), it motivated the T29 heavy tank, before the liquid-cooled designs fell out of favor, being replaced by air-cooled engine designs.
While time has largely forgotten the flat-plane GAA V8 engine, we’re doing our best to remind everyone that before the Voodoo, Ford had another all-aluminum DOHC flat-plane V8 engine that made 525 horsepower. If you want to see some in-depth technical manuals of the time, check out TheShermanTank.com, which has done an incredible job of compiling technical data, drawings, and information about the GAA engine and keeping it alive on the internet.