Indian “Upside-Down” Four


  • Soon after the death of William Henderson in 1923, Indian expanded its product line with the purchase of the assets of the Ace Motorcycle Company
  • By 1936, the Indian/Ace evolution continued with the introduction of the “upside-down” four engine many considered a step in the wrong direction
  • Many considered the engine “industrial looking” and it required a heat shield over the exhaust to prevent rider leg burns
  • By 1931, Indian replaced the Ace frame with the Indian double-downtube frame, upgraded the front brake, replaced the rear frame section with one patterned after the 101 Scout, increased the wheelbase, and redesigned the fuel tank
  • The nickname was derived from the new valve arrangement where the exhaust valves were now on top of the motor (for improved cooling) and the intake valves were located on the side (for improved combustion)