Metallurgy, engineering, induction and exhaust flow knowledge being what is was in the 1940’s it was not easy to make a competitive V-twin engine that would also endure 200 miles of professional dirt track racing. Bearings, pistons, valves and connecting rods all suffered failures. The Indian “Big Base” Scout engine was a special race-only engine that incorporated some secrets learned on the track, put them in play for pre-World War II and early post War racing eras and kept Indian competitive against its rival, Harley Davidson. Indian Scouts were ridden to many wins by Indian Wrecking Crew riders Bobbie Hill, Bill Tuman and Ernie Beckman. Earlier, in 1948 Floyd Emde won the Daytona 200 on a 648 Big Base.
Experts say there were two batches of Big Base engines with about 40 to 50 engines made complying with AMA rules which called for a minimum production of 25. The initial batch was in 1939, and then later 648 Big Bases came in 1948. In appearance, Big Base crankcases were similar to standard Sport Scout units. The outward differences being a smaller triangular internal cavity near the lower rear portion of the crankcase and a shallower case for the timing gears. Inside you can see much beefier crankshaft bearing bosses. Designed by Indian factory engineer Allen Carter, this triangular cavity held oil from a “scraper” that skimmed oil off the spinning flywheels reducing rotational friction, blow-by and oil foaming. This triangular area is hard to see, tucked in behind the primary exhaust. Another difference; the 1939 engines were sand case, the later batch for the 1948 were die cast like production Scout crankcases.
This Big Base Scout built by master tuner Erwin “Smitty” Smith of Rock Island, Illinois is most amazing in that it’s built up entirely from extremely rare new parts that Smitty kept from the end of the Scout’s racing days, “new old stock”. He must have had a great smile on his face as he assembled the “holy grail” of Indian racing parts into one more, probably the last wonderful Indian 648 Big Base Scout.
- Engine: 45 Cu. In. (750 cc’s) Side-valve 42 Degree V-Twin
- Magneto: Splitdorf
- Carburetor: British Amal / Smitty’s Air Cleaner Shield
- Transmission: 3-Speed
- Primary: Roller Chain
- Horsepower: Approximately 50
- Suspension: Girder Fork, Rigid Rear