| November/December 1982

Thumb screw type speed changer

Fig. 15: Thumb screw type speed changer

This is the second and final part of an article written by Wayne Grenning of 318 Summit Street, Boonville, New York, 13309. The article was begun on page 4 of the September/October 1982 issue of GEM. Part One of the article covered the development of the 1 HP IHC 'M' engine; this part goes on to explore the development of the 3, 6 and 10 HP models.

3 Horsepower: 1918

Production of the 3 horsepower type 'M' engines began in 1918 and continued through the Great Depression until 1937 (see figure 17). The very first few 3 horsepower 'M's used only one pushrod. Both exhaust valve and ignitor were operated by this single pushrod, which was quickly discontinued. The two push rod version was then adopted. From 1918 to approximately 1922, the 3 horsepower unit was built with the type 'L' low tension rotary gear driven magneto (see figures 4 and 5 in S/O 82 GEM). It was the same in every way as the magneto used on the 1 horsepower 'M' except for the number of teeth on the gear. Location of the drive gear was also within the crankcase. The engine was only offered in the kerosene version unlike the 1 horsepower. Carburation consisted of the two needle valve unit, one for fuel on the right and water on the left. It operated almost in the same way as the 1 horsepower engine.


As with the 1 horsepower 'M' the 3 horsepower underwent similar changes. International offered the high tension American Bosch magneto, but only 1000 of these were built with this option between the years 1923 and 1932. White metal was used instead of cast iron for the fuel pump and the needle valve heads.

A new carburetor was added. It featured three needle valves, a take apart body, and individual chamber drains for kerosene, gasoline and water (see figures 8 and 9 in S/O 82 GEM). The crank-case hatch was changed from the butterfly fastener to four machine bolts.

The Wico type 'EK' magneto was offered with the engine in addition to the American Bosch type 'S' (see figures 12, 13 and 14 in S/O 82 GEM). At the same time the International Harvester type 'L' rotary low tension magneto and ignitor were retired. The spark plug was positioned on the governor side of the head and to the left of the intake valve. From the years 1918 to 1922 a total of 75,310 3 horsepower engines were built with the type 'L' magneto. Later, 27,885 engines were built with either the Wico EK or the American Bosch 'S'. In 1937 the list price was $95.00 and only 48 units were built. A total of 103,195 3 horsepower engines were manufactured in 19 years of production.

6 Horsepower: 1918

International Harvester offered the 6 horsepower 'M' to the public in 1918. The developments and design of this engine paralleled the 3 horsepower unit except for the following items: 1) The magneto was a low tension International Harvester type 'R' rotary gear driven unit, (see figures 18 and 19 The ignitor was the same as the 3 and 1 horsepower units. They were in fact interchangeable) 2) The Flywheels had dogs to which a flat pulley or clutch was bolted. 3) The head was always water cooled.