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Liberty L-8: The Scaled Down V8 Variant of the Iconic Liberty V12 From WWI

It's V8 Month here at autoevolution. A month-long celebration of all the engines with eight cylinders arranged in a V-formation and all the wacky designs therein. That isn't just limited to things with four wheels and tires. It includes airplanes as well.
Liberty L-8 National USAF Museum 7 photos
Photo: National Museum of the United States Air Force
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Sadly, acceptable aeronautical performance figures are more or less out of reach for a typical gasoline V8 engine these days. However, you'll still see the occasional DIY guru swap an LS engine into a Cessna of some sort. More on that another time. But in the early days of combat aviation, when the automotive and aeronautical sectors had far more overlap, quite a few aircraft used V8s as their primary propulsion.

Be it German, British, or French airplanes, each of the main combatants of the First World War's Western Front wielded their own flagship aeronautical V8 in the skies above the trenches. This eventually included the Americans. Of course, the U.S. military would take over two and a half years from the start of the fighting in Europe to finally enter the war. One the nation initially wanted nothing to do with.

By the time the U.S. finally deployed to the Western Front in April 1917, they were prepared with an engine to power everything from tanks to airplanes and even racing cars when the war ended. The engine in question was the brainchild of one of America's first iconic aeronautical engine designers, a man called Jesse G. Vincent. His most famous creation, the 12-cylinder L-12, is well remembered and well celebrated. But it also had an eight-cylinder cousin, one of America's first iconic V8s on land or in the air.

As the grandson of an American Civil War railroad engineer, you could argue that Jesse Vincent was born for this kind of work. He himself attained the rank of chief engineer of the Hudson Motor Car Company by 1910 before joining Packard in 1912. If not for the First World War, Vincent would have likely never left Packard for any length of time, as his presence in the company would go on to pay huge dividends after the war. His input was pivotal in the construction of the Packard Proving Grounds in Southeastern Michigan, the first such facility intended for the use of testing automobiles.

Liberty L\-8
Photo: National USAF Museum
But alas, Vincent couldn't avoid the beating drums of war, and found himself commissioned as a Major in the U.S. Army Signal Corps shortly before America itself entered the conflict in 1917. It was during this time that, with help from Elbert J. Hall of the Hall-Scott Motor Company, Vincent designed blueprints for the L-12 engine. Devising a full schematic in for the new V8 a scarcely believable five days. Now that's some back-of-the-napkin engineering, if there ever was any.

With dimensions of 1,649-cubic inches (27 liters) and sporting twin duplex Zenith carburetors capable of jetting 400 horsepower, the L-12 was an easy-to-manufacture powerhouse that had World War I not ended in an armistice, would have almost certainly gone on to power every Allied warplane henceforth. Even so, more than 20,000 Liberty L-12 engines were manufactured. But to say a V-12 was the only configuration the Liberty engine appeared in would be false.

Of those 20,000-plus units, fifteen prototypes of L-8 V8 engines were manufactured beginning in 1917. In truth, the L-8 came not only before the L-12, but also before the prototype four and six-cylinder variants were conceived after the L-12's production had already wound down. To further blow your mind, the L-8 actually found its way into an aircraft before the L-12 in August 1917.

The L-8 was essentially the same engine block and internals, with two cylinders and all their hardware omitted to form a V8. With a bore of five inches (127 mm), a stroke of seven inches (178 mm), and a dry weight of 575 pounds (261 kg), a total power output of 270 horsepower at 1,700 rpm on first test run was pretty darn impressive for the day.

Liberty L\-8
Photo: Flickr
Over time, fine tweaking to the timing, fuel-to-air ratio, and compression saw this power figure rise to 330 horsepower. In spite of this impressive figure, serious vibrational problems plagued the engine under hard acceleration. After being contracted out to automakers like Buick, Ford, Lincoln, Packard, and Marmon, who managed to crank out 15 at the cost of $3,000 each ($69,439.69 in modern money), it was decided that existing V8 aeronautical powertrains like the Hispano-Suiza 300-hp engine were preferable to a downsized American Liberty engine.

Ultimately, only seven aircraft ever received a Liberty L-8 engine. Six Pomilio FVL-8 bi-planes and one Engineering Division USB-2. Today, surviving examples of the Liberty L-8 are on display at the Conneaut Lake Historical Society in Conneaut Lake, Pennsylvania, the Smithsonian National Air & Space Museum in Washington D.C., and one is in storage on the sight of the National Museum of the United States Air Force in Dayton, Ohio.

Check back soon for more from V8 Month here on autoevolution.
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