Willys-Knight Hubcap, circa 1930

Willys-Overland introduced the mid-priced Willys-Knight for 1914. Willys-Knight cars used sleeve-valve engines throughout their 19-year production run. Unlike common poppet valves operated by cams and springs, sleeve valves sit inside the cylinders -- forming "sleeves" around the pistons -- and work via sliding or rotating motion. They make for a quieter engine, but they consume more oil.