Farmall M Timing Marks

My M has 5 marks on the pulley. Turning clockwise you have 1
mark followed by 2 marks very close together. Then there are
2 more marks spaced a little farther apart. Which mark is TDC
so I can set timing and valves???

Can't be sure without seeing but sounds like you have a later crank pulley or a engine change. If so the first mark you came to was 40 degrees BTDC. next 30, next 25, next 16 then TDC. May want to remove the # 1 cylinder spark plug and stick something through the hole to see when the piston tops out to see if its near the mark.

I will try to post a picture

Here is a picture

agree, you can find tdc by removing plug and top out piston. eliminate the guessing, piston position and mark will answer question.
have did that many times.

Once you determine top dead center mark like was told, I can tell you that 22 degrees before top dead center is l 7/16 before that. Fire crater pistons are timed to that mark at full throttle. Some one may have marked off the 40, 30, 25 and 22 or maybe even 16. Hard to tell but they can all be figured out pretty easy with a little math.

The one you have near the pointer should be TDC.
Pulley was replaced or a change of some kind was made sometime. That pulley didn't come out until 1956 I think it was.

(quoted from post at 17:53:02 08/24/13) Once you determine top dead center mark like was told, I can tell you that 22 degrees before top dead center is l 7/16 before that. Fire crater pistons are timed to that mark at full throttle. Some one may have marked off the 40, 30, 25 and 22 or maybe even 16. Hard to tell but they can all be figured out pretty easy with a little math.

Click to expand...

Based on Pete's info and with a little backwards math I concluded:

Pulley diameter is roughly 7.49" calculated from backwards math (I do not have precision equipment to actually measure it but that backwards math calculated diameter seems to be rather valid on a quick double check using my eyeballs and a crude tape measure and my standard ole Farmall M as a reference).

22 degrees is 1.438 inches (or roughly 1 7/16") from TDC mark.
30 degrees is 1.960 inches (or roughly 2") from TDC mark.
40 degress is 2.614 inches (or roughly 2 5/8") from TDC mark.

(Note: Use a flexible tape measure and follow the pulley circumference shape to measure the mark from the one you determine is TDC. Knowing which mark is TDC on #1 cylinder is crucial. Even if you have to remove the #1 spark plug and improvise use a common drinking straw and remember to be on compression stroke while an assistant turns the engine over by hand -then you will be able to easily tell which mark is actually TDC).


If you want the formula that I used to figure your own degree setting then use the following formula:

(7.49) x (3.1415) x (your desired degree number) / 360 = the inches from TDC mark