The Indian Four 1927 to 1942
Henderson and the Indian 4 (Ace)
The Indian Four began in 1927 when Indian purchased the Ace Company.
In fact for the first year or so the bike was called the "Indian Ace". (The Ace itself had been developed by the same engineer, one Will Henderson, who had designed the Henderson four. When Henderson was bought out by the Schwinn Excelsior Company he left it and in 1919 started the Ace company, building a very similar inline four cylinder engine bike which was bought out by Indian in 1927.
The Henderson Four died in 1931 and the Indian Four in 1942.
The only engine difference between the early Indian and Ace Fours was that the Indian had five instead of three main bearings.
Over the years the sheet metal on the Indian grew more massive.
In 1936 and 1937 only, the F head (inlet over exhaust valve) was reversed. This "upside down" experiment everyone considers a mistake.
Most Indian Fours had one carburettor at the very back to cool the rear cylinder. The downside is that not much fuel and air mixture is left for the front cylinders.
In 1938 the company did a major redesign of the Four, generally considered a big improvement, but they did not take the opportunity to go to full OHV (still an F head) nor to go to multiple carburettors, nor to increase the displacement.
Displacement of the Four was always just over 77ci or 1260 c.c.
Overheating rear cylinders;
On the Henderson, Aces and Indians, it is rumoured that the rear cylinders overheat and that crankcase oil dispersion is inadequate. Tests using modern instruments on a 1940 Indian Four have proven this to be not the case.
The late Fours (1938-42) actually run quite cool. All the Fours suffered from clutch drag and gearbox wear.
Indian could not afford to revive the 1942 Four after the war.