09/02/2026
We told the Whippet to Go-Devil story earlier on this page. Thirty HP economy car engine evolves into sixty HP military engine that powers 640,000 Jeeps across every theater of World War II. Eisenhower's three tools that won the war. What we didn't tell was the name of the man who made it happen. Not a committee. Not a corporate program. One engineer: Delmar G. "Barney" Roos. Born in the Bronx in 1888. Cornell University dual degrees in mechanical and electrical engineering. Fencing champion. Award winning photographer. Veteran of Locomobile, Marmon, and Pierce-Arrow. Chief engineer at Studebaker for eleven years. The most overqualified man who ever worked for a company that couldn't afford drafting paper.
Roos arrived at Willys-Overland in 1938 after a brief consulting stint with Rootes in Great Britain. The company he walked into was barely alive. The Great Depression had nearly destroyed Willys-Overland. The factory in Toledo had been partially sold off for operating cash. The engineering budget was close to zero. The only engine in the company's portfolio was the ancient Whippet Four from 1926, a 134.2 cubic inch L-head inline four that had been making 30 HP when it debuted and was up to approximately 48 HP after twelve years of incremental improvements. Roos had one engine, no money, and a chairman named Ward Canaday who berated the engineering department for using too much drafting paper. The story, sworn to be true by multiple sources: Canaday lectured Roos that once a company asset landed in the waste basket, it was worthless. Roos lifted Canaday up and placed him in the waste basket. Canaday reportedly took it in good humor. Or at least he didn't fire him. The man who would build the engine that won World War II dealt with his boss by putting him in the trash. That tells you everything about Barney Roos.
With no budget for a new engine, Roos modernized the Whippet Four using every engineering trick that could be executed on existing tooling. Insert bearings replacing poured babbitt bearings, a technology that reduced friction and improved durability dramatically. A counterweighted crankshaft replacing the unbalanced original. Lightweight 340 gram aluminum pistons reducing reciprocating mass and allowing higher safe RPM. Full pressure lubrication replacing the splash system that had been barely adequate in 1926. A revised cam lobe design with improved valve timing. Updated valvetrain geometry. Improved breathing through revised port work. The bore and stroke stayed the same: 3.125 by 4.375 inches. The displacement stayed the same: 134.2 cubic inches. The external dimensions stayed the same so the engine could be built on the same production tooling. Everything that made the engine work better changed. Everything that would cost money to retool stayed the same. Roos squeezed 62 HP at 4,000 RPM out of an engine that had started life at 30 HP, using the same block, the same bore, the same stroke, and the same factory tooling. The engine went into production Willys passenger cars in 1939. It was named the Go-Devil in 1940. The name meant "goes like the devil," a polite way of saying "goes like hell."
When the U.S. Army issued its specification for a lightweight reconnaissance vehicle in 1940, Roos dropped the Go-Devil passenger car engine into the Willys prototype with minor modifications to military specifications. The engine was reportedly the star feature with the Army brass. The Army needed an engine that could start in arctic cold and run in desert heat. That could ford rivers without drowning. That could be repaired by conscripted mechanics who had been farmers and clerks six months earlier. That could run on any available fuel quality in any theater of operations. The Go-Devil did all of it because Roos had designed it to survive the most hostile operating environment available to a civilian automobile, the American consumer, who neglected maintenance, ignored oil changes, and drove through conditions that no engineering specification anticipated. If the engine survived American car owners, it could survive the European and Pacific theaters. It did.
Ford manufactured exact copies of the Go-Devil engine under military designation L-134 alongside Willys-Overland production. Over 640,000 Jeeps were built before the war ended in summer 1945. The same engine powered the first civilian Jeep, the CJ-2A, in late 1945. It powered the Willys Station Wagon in 1946. It powered the Jeepster in 1948. "Brothers under the hood," the ads said. The Go-Devil remained in production through 1965, built by Willys-Overland, then Willys Motors, then Kaiser Jeep, spanning twenty six years and three corporate identities. The overhead valve Hurricane four that gradually replaced it starting in 1950 was an F-head conversion of Roos's Go-Devil. The engine that replaced the Go-Devil was still the Go-Devil, with the valves moved from the side to the top. Roos's architecture survived even when the valvetrain changed.
Barney Roos didn't just build the Go-Devil. He built the engine that made Jeep possible. Without a competitive powerplant in the 1940 Army trials, Willys-Overland would have lost the contract to Bantam or Ford. Without the contract, the company would have died. Without the company, there would be no CJ, no Wrangler, no Cherokee, no Grand Cherokee. No Jeep. The brand that became synonymous with American off road capability exists because a Cornell fencing champion from the Bronx arrived at a bankrupt company in Toledo, put his boss in a trash can, and modernized a twelve year old economy car engine using zero new tooling and zero budget. Thirty HP became sixty. Sixty HP won a war. And the man who made it happen never became famous because the vehicle he powered became more famous than any engineer ever could.
