Timing a Farmall A

I need some help. I took my magnito out of my 1940 Farmall A. Had a magnito man check it and he said it had a strong spark. The book says to turn it over till you get compression on # one cylinder. Then it says to go underneath to the fly wheel and look for the timing mark. But I can't find the mark its supposed to line up with. I thought I had it done but I can't get it to fire. Sure could use help. Thanks, Randy

The mark is hard to find. You can take off the valve cover to see when #1 is on compression and with spark plug removed you can look in the hole to see when the piston is at the top. Your rotor on the mag should point to the 2 oclock position then. It fores on TDC then goes to 32deg advance when engine runs. There is no advancing of the timing by turning the mag.Are you sure the gear that turns the mag wasnt removed or you could be way out of time. You could remove all the plugs and with the cap off the mag observe when the rotor snaps to make sure every thing is ok. When working on a new to me tractor i will remove the plugs so the engine turns over easy and hook up the spark plug wire to a plug and with my finger in the hole can watch the fire when i feel compression.

Thanks Gene, I did replace the gears that turn the mag. I lined up the gear with the single tooth mark between the gear with the two teeth mark.

Stick with the book and you'll get it done.

As far as finding that mark so that you know it's right at TDC on the compression stroke . . . It doesn't end when you begin to feel compression. All you've done to that point is determine that you ARE on the compression stroke. You need to continue turning the motor until you reach the top of that stroke.

Pull your #1 plug, stick your finger in the plug hole and turn the motor until you begin to feel compression underneath. Take your finger out and get a light. Continue turning until you see the top of the piston. Watch it until you can see it sitting at the top. Ideally that's TDC but there's a few degrees of turn on the crank where it's hard to detect any motion at the top of the piston.

One trick is to stick a stiff wire in through the plug hole so that it rests on top of the piston and the bottom of the plug hole, something long enough that it sticks a ways out the plug hole without overbalancing. As the piston comes up, the outer end of the wire goes down. When the outer end of the wire is at its lowes, the piston is at TDC, with the same margin of a few degrees error. If you use this method and go past turning it with the crank, you can pull it back using the fan belt.

As far as the mark itself -- you won't see it when you first start feeling compression through the plug hole. You will need to very near TDC to ever see it. The mark is only visible through the hand hole on the bottom of the bell end of your torque tube, so you do need to be very near TDC to begin with. The mark is nothing put a fore-and-aft line on the wide surface of the flywheel. Even when it's all cleaned up it can be difficult to see. I've seen enough variation in them, I could never decide if they were machined or stamped in, but I can say that IHC didn't wear out any more tooling than they had to puttin' em there.

If you can get near TDC using the wire trick, you should be able to find the mark. It will take a light and likely some solvent and a stiff toothbrush-style brush -- wire is better than an actual toothbrush. For best lighting and brush access, remove the halfmoon cover under the rear of the motor, and start looking and scrubbing. If you get it altogether clean, you'll see that the line is stamped TC on on side and 1-4 on the other, but be sure to clean it up at the end of the line nearest the motor.

When that line is at dead bottom, pistons 1 and 4 will be at TDC. You will have verified that #1 is at the top of its compression stroke with the finger in the whole and wire tricks. To verify that the mark is at dead botttom, first dab some durable paint on the front end of the line that you cleaned up, then replace the halfmoon cover. Depending on which cover you have, your paint mark should align with either the vertical line in the stamped cover, or the nub cast into the inside of the cast cover.

When lined up in that fashion, you are good to go with the timing instructions in your manual.

See my note above re general getting there, but what your note here describes, you may find your timing out by 180*.

The SINGLE punch mark on the cam gear lines up with the single punch mark on the crankshaft gear. Alignment between the cam and governor/ignition gears is made on the DOUBLE punch marks.

Thanks for the help. I'm going to wait for warmer weather and check it out.

You are going to remove the gov housing again as the dots arent correct if you placed the single dot on the gear between the two on the cam gear. The SINGLE on the cam gets lined to the Single on the gov gear you are way out of time the valves arent even close to make it run. When the dots are lined up correct not only is the gear that runs the mag in time the camshaft itself is way out of time. You need a good lite and clean up the cam gear good to find the single dot. Remove the plugs so you can turn the engine over with fan or crank its going to be fun but you can do it. ifn ya needs some help you can call 319-430-3907

When No1 piston is at TDC on the compression stroke both valves on No1 piston should be closed. Then rotate the rotor to the No1 plug tower which is about 1 o'clock and then install your mag. Hal
PS: Once you feel that compression against your thumb drop a long plastic straw on top of the piston and you watch the straw rise as a helper hand cranks the engine slowly.

To many football games the gov gear has the two dots and lines up with the two dots on the cam gear. They can be hard to see sometimes.