IHC-TYPE ‘M’

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.

1923

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.

1923

The wing nut type rear access hatch fastener was changed to the
plate and four machine bolts, (see figures 6 and 7 in S/O 82 GEM).
White metal was used for the fuel pump casting as in the needle
valve heads. Two part construction and three needle valves were
used on their ‘improved’ carburetor. The rotary type
‘R’ drive gear was also cast in white metal. (Drive gears
similar to this appeared intermittently on the smaller horsepower
units.)

1924

High tension ignition supplied by the Wico EK or the American
Bosch ‘S’ replaced the type ‘R’ low tension magneto
and ignitor. Only 491 6 horsepower engines were sold with the
American Bosch rotary magneto. The remainder were equipped with the
Wico type ‘EK’. (see figures 12, 13 and 14 in S/O 82 GEM)
When production of the 6 horsepower ceased in 1937 the list price
was $165.50. A total of 56,788 engines were manufactured in the 19
years of production between 1918 and 1937.

10 Horsepower: 1920

Production of the 10 horsepower type ‘M’ started in the
middle of 1920 and continued into the 1930s. Low tension ignition
was supplied. Type ‘U’, ‘O’, and ‘OL’
International rotary impulse magnetos were commonly used, (see
figures 20, 22 and 23). The tripping mechanism for the ignitor and
the magneto itself were both exposed on the outside of the engine.
A long push rod directly connected the ignitor to the impulse trip
arm located on the end of the armature shaft of the magneto. This
push rod was used so the ignitor would be struck the instant the
magneto was tripped, (see figure 21)

In this early production the 10 horsepower version was also
manufactured with two needle valves, a one piece carburetor, a cast
iron fuel pump and wing nut type crankcase access hatch. As with
the 6 horsepower unit the 10 horsepower offered machined dogs on
the flywheel for the mounting of a pulley or clutch.

1927

In 1927 International discontinued the use of the low tension
type ‘U’, ‘O’, and ‘OL’ magnetos, (see
figures 20, 22 and 23) These were replaced with the Wico
‘EK’ and the American Bosch ‘S’. (see figures 12
& 13 in S/O GEM) Only 317 10 horsepower engines were
supplied with the American Bosch ‘S’ ignition. The
⁷/₈ inch thread spark plug was mounted on the
magneto side of the head and recessed at an angle. Water was used
to cool the engine head. Like other ‘M’ engines the fuel
pump and needle valve heads were changed to white metal. The
carburetor was changed to the two piece design with three needle
valves. In 1933, only 18 10 horsepower engines were built. However,
they were sold as late as 1936 for a list price of $320.50. During
the 13 years of production only 6249 of these units were built.
From the beginning, the 10 horsepower ‘M’ was the only
engine that offered a partial base.

TIMING OF THE IGNITION AND VALVES

To help collectors of International and McCormick Deering type
‘M’ engines, included is a procedure on ingition and valve
timing.

Figure 24 shows a diagram and specific timing marks for valves
and ignition. The following procedure is recommended to adjust
these engines: 1) Turn the flywheels clockwise so that lines
‘A’ on the flywheel align with ‘B’ on the
crankcase. 2) The ignitor should be at the immediate point of
tripping as shown with push finger ‘E’ and ignitor
‘F’. 3) At the same time align factory scribe mark
‘J’ on the magneto bearing with scribe ‘I’ on the
end of the magneto armature shaft. They can align either way. 4)
Without turning the flywheels, marks ‘C’ on the
eccentric-plate should be in line with mark ‘D’ on the side
of the magneto bracket and also with the center of the magneto
shaft. Scribe marks ‘I’ and ‘J’ must align
perfectly to allow for the peak electrical current to be in
synchronization with the tripper of the ignitor. (If ‘I’
and ‘J’ do not line up when ‘A’ on the flywheel is
in line with ‘B’ on the crankcase, the magneto gear should
be shifted forward or back so that the scribes come in line.)
5)Rotate the flywheels slowly by hand until push finger ‘E’
is between 5/32′ and 3/16′ from the ignitor lever
‘F’. (see figure 25) At this time the push finger should be
in the farthest position from ‘F’. 6) If an adjustment is
necessary, the trip finger and rod ‘E’ may be turned one or
more turns after loosening the nut and screw ‘C’. If the
above adjustment was necessary then ‘A’ and ‘B’
should be checked again to make sure the spark still occurs at the
proper point. 8) The tripping of the ignitor is adjusted by either
adding or removing shims at ‘H’.

In reference to figure 24, the exhaust valve should close when
‘B’ on the crankcase is in line with ‘N’ on the
flywheel. Adjustment for this is made by turning pushrod
‘L’ one or more times either way, after loosening lock nut
‘M’. Lengthening the rod allows the exhaust valve to open
earlier.

To further help International ‘M’ owners with the
identification as to the date of manufacture of engine, a serial
number list of all ‘M’ engines is supplied.

Research for this writing has been taken from original
International Harvester manuals, catalogs, documents, books, sales
literature, and engine collectors. The possibility for mistakes in
my history of the ‘M’ engines exists, although I have done
my best to write an accurate article. Correspondence concerning
this article, corrections and the International model ‘M’
farm engines will be graciously received. All letters containing
self-addressed, stamped envelopes will be answered.

SERIAL NUMBERS FOR IHC TYPE ‘M’ ENGINES