Janicholson Timing marks on an H

Jim, let me start off by saying I don't know the correct answer to this, and it gets brought up on here from time to time, with different answers.

You recently posted: "The first mark is the timing for advance, the second is TDC. there is no need for marks after TDC. Jim"

Couple of problems with that.

Factory "spec" is total running advance of 40º, (battery ignition) and the marks are too close together to indicate 40º of advance, and the IH Blue Ribbon Mag manual doesn't agree either.

It states:

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/IH/Htim_zps83ac256b.jpg">

NO explanation of what the second marks is for.

So, WHAT's the truth, here, inquiring minds want to know!
Page 44

Like I said before many times on here. The two marks that are close together, the first one coming up when turning the engine in the normal direction of rotation is top dead center for number one cyl and number 4 cyl. The next mark is 5 degrees after top dead center. As the book indicates a 40 degree spark lag in magneto and you want a 35 degree of advance when engine is running, you set the magneto to trip the impulse at that 5 degree after top dead center mark. Now you will have the 35 degrees advance when the engine runs. The spark lag, or impulse lag holds the shaft that has the lobes for opening the points from turning until impulse trips. By that time the piston is on it's way down so it does not kick back. There are no factory marks indicating the total advance while running. There is one other factory mark all by it's self on the pulley of an H that is for lining up the pilot bearing grease fitting in the flywheel. Over the years, marks may have been added to the pulley by someone. I have added a lot of them when I install battery ignition units or when installing fire crater pistons. Different compression ratios require different total advance and the critical timing is when engine is running full throttle, therefore to check the advance with battery ignition units, thus the added markings. With a magneto you have no control over spark advance. Once the impulse kicks off the spark is fully advanced. That is the chief disadvantage of a magneto. On battery ign the advance is gradual with increase of engine speed and the maximum amount of advance is controlled with the slot in the distributor shaft and the rate is controlled with the springs. You can always add marks to any degree you want on the pulley by calculating the circumference of the pulley if you want to actually check to see how far the spark is actually advancing. Who knows what impulse coupling has been installed in that magneto over the years. Different ones have different lag.

I am beyond corrected into "Convinced" of the errors of my ways. Too many vehicles, too many marks, and too far away from my H. (650 miles)

I believe your post to be essentially correct, yet the official IH Blue Ribbon Mag Service Manual (GSS-5035) states to time the tripping of the impulse to TDC, (The "H" is specifically included in that recommendation) and the manual makes NO mention of the second (5º ATDC?)mark.

So there IS a bit of mystery here, still!
Pages 43 and 44


http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html

To get to the bottom!!!
A method of putting the piston at TDC is to use a stationary fake spark plug that extends into the cylinder to touch the piston. Then the crank is rotated (by hand only plugs out, battery disconnected) till the piston stops. A mark is then made on the pulley at the indicator.
The engine is rotated the opposite direction as above till again it stops. Mark is made as above. 1/2 of the way between these marks is TDC.
The purpose for the retarded position of the Mag timing mark is to limit liability when hand cranking. a kickback from any advance forward of TDC will be dangerous to the cranker. Jim.

Bob that's something I always wondered about also. Other manuals besides yours say the impulse should trip at TDC when cranking by hand. If I remember correct not all pulleys have the second mark also.
Always set them on TDC but never hand cranked one even for fun so hope you get a consensus on the what's correct. If I remember correct the original H mag has a 35 degree advance.

I don't remember the book, or bulletin or what but clearly remember being instructed to have mag trip on the 5 degree after. It is a safe distance and from having many of those magneto's on a test bench over the years they have more than a 35 degree lag. That machine was junked many years ago so I have no way to prove that but a marked pulley will easily show you how much advance you have. Like anything else, subject to wear. As the dowel the weights stop against wears, along with the tips of the weights and the wear in the pivot of the weights, the lag changes some.

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.

[u:c39ef536ad]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.[/u:c39ef536ad]

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