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1929 Willys Knight 56

The Sleeve Valve Engine, Rectified

Production Years: 1928-1929
Country: United States
Number Produced: 37,931

In 1927, the Willys-Overland car range saw a groundbreaking addition with the introduction of the Type 56, a luxurious sedan featuring a six-cylinder Silent Knight engine equipped with a rectifier. Willys, an early American manufacturer, had integrated the Knight engine into its lineup since 1914. This innovative step was aimed at addressing the sleeve-valve engine's notoriety for excessive oil consumption, a trait often associated with Silent Knight engines that left a distinctive trail of blue smoke.


Willys-Knight ingeniously tackled the oil consumption issue by directing excess oil through openings in the cylinder wall near the exhaust port. The resulting mixture of oil and gasoline was then channeled to the rectifier, where distillation occurred in a chamber heated by exhaust gas. This unique process allowed the return of oil to the crankcase, while expelling gasoline fumes through the exhaust pipe. Despite its clever and effective design, the rectifier was not incorporated into engines used in Europe.

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