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History of the Willys Go-Devil Engine

Of the three prototype Jeep designs of 1940, the Willys-Overland sported the most powerful engine, an advantage that also made it the heaviest vehicle, nearly losing it the bid by exceeding the Army’s weight limit. However, it ultimately won the bid, making the Willys 134ci Go-Devil 4-cylinder a part of the Jeep legend.

Willys’ part in the story might have turned out differently had it not been for Willys-Overland chief engineer Delmar G. “Barney” Roos, who had the job of revamping the unreliable Willys four on a budget shortly before WW2.

Roos and his staff set upon modernizing the engine by incorporating insert bearings, aluminum pistons, a fully counterbalanced crankshaft, a revised valvetrain, and a fully pressurized lubrication system. In just a few months, the new engine exceeded 100 hours at over 60 hp 4,400 rpm. Christened the “Go-Devil”, and new engine first appeared in some of the 1939 Willys cars. In 1940, when the new Willys 440 models appeared, they were all powered by the Go-Devil, as were 1941’s 441 and 442.

Later in 1940, Roos spearheaded Willys’ entry into Army bid. One of the critical parts of the Willys’ involvement was Roos’ choice to press for the bigger engine despite the military’s weight penalty. Roos’ decision was vindicated when the standardized jeep gained the necessary weight to be the durable war vehicle the Army desired.

The Go-Devil lived a long life, from pre-WW2 Willys cars, to WW2 and Korean War military jeeps, to DJ 4x2 Jeeps through 1964. Jeep station wagons and trucks even used them through mid-1950s, and they were used as commercial, marine, and stationary engines.

Ultimately, the Go-Devil was in American production at least into 1965, and was built under license in Argentina, Japan, and France. In 1952 Willys introduces the- F-head four cylinder, also a Roos design, which was largely modeled on the Go-Devil block, and saw production through 1971.

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