First on most H's or M's there are 3 marks on that pulley. The mark all by itself when aligned with the pointer allows one to grease the pilot bearing from underneath the tractor. That is all it is used for.
Of the 2 marks together: think of that 2nd mark as only a visual indicator only in most cases and at minimum it keeps you from confusing it with that other stand alone mark which you would easily do if it were not there. If you have a distributor in your tractor then no chance you will use that 2nd mark for anything other than as a visual indicator. If you have a magneto then I guess you could use that 2nd mark but it likely depends on the procedure you are following. The IT manual does not use that 2nd mark. But I have heard of people purposely retarding the timing a bit if you plan to hand crank so you do not get a broken arm from engine kickback if timed too aggressively.
The first mark of the 2 marks that are close together is #1 cylinder at TDC.
If you plan to time your tractor without the engine running then these are all the marks that you need and you can follow IT manual procedure or IH static procedure accordingly.
Unfortunately, if you want to time your engine running then you will need to account for the advance in the distributor (if you have a distributor) by adding you own timing mark with either a white paint pen or liquid paper whiteout correction fluid that typists use works too.
To do this you need to some math and have a flexible tape measure that you can use to follow the perimeter circumference of the pulley.
Most H's have a crank pulley that measures 6.5 inches in diameter.
For a desired 40 degrees setting on a Farmall h: measure 2.269 inches (or 2 and 9/32 inches) by following the perimeter of the pulley with a flexible tape measure in the advanced direction from TDC mark and add your mark with a paint pen. Use a timing light and align with your mark with engine running.
For your own custom degree calculation on a Farmall h which you may need to do if you have high compression pistons then use the following formula:
6.5 x 3.1415 x (your desired degree) / 360 = value in inches from TDC mark for you to place your mark
Most M's have a crank pulley that measures 7.49 inches in diameter.
For 22 degrees on a Farmall M: 1.438 inches (or 1 and 7/16 inches) advanced from TDC mark make your mark with paint pen.
For 30 degrees on a Farmall M: 1.960 inches (or 2 inches).
For 40 degrees on a Farmall M: 2.614 iches (or 2 and 5/8 inches).
For your own custom degree setting on a Farmall M use this formula which you may need to do if you have high comprssion pistons:
7.49 x 3.1415 x (your desired degree setting) / 360 = value in inches for you to place your mark.
Note1: Timing should be done at Wide Open throttle on the Farmalls when using a timing light.
Note2: Ideally it is a good idea to verify your wide open throttle setting is close with a tachometer (I use a hand handheld and measure off the PTO shaft to set both idle and WOT governor settings). At unloaded WOT on a Farmall H or M you should be close to 600 rpm on PTO shaft.
Some Farmall M specs
Low idle: Engine - 425; PTO - 158
Rated speed: 1450; PTO 540
High idle: 1595; PTO 594
This post was edited by rankrank1 at 17:47:58 12/14/13 8 times.
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