How to time a Distributor?

I am changing from a mag to a distributor and changing to 12 volt. And I am curious how to time the distributor.

I wouldn't toss a good mag, but that is your business. BEFORE you remove the mag, set #1 on TDC, and check against timing marks. Point the rotor in the dist to the #1 terminal. Remove the mag and install the dist, without moving anything and rotate the dist CC, viewed from the rear. Remove the coil wire from the dist, hold wire next to the nut on the dist, rotate clockwise until you get a spark, check alignment of timing marks. Lock it down and confirm by rotating engine one revolution (preferably with a hand crank) until it sparks again, the timing marks should be lined up. You can do this without the timing marks, I prefer to use them as a check.

I don't plan on tossing the mag, it will be kept on a shelf. Where are the timing marks located?

What are you working on? but anyway the marks should be on front crank pully.should be a pointer there also probably off front engine.

Sorry forgot to add that, I am working on a Bn!

On the BN, your only timing mark is going to be the TDC mark on the flywheel. Unless the tractor's been split and cleaned up, it can be hard to find. It's a line that runs fore and aft on the flywheel, marked T-C 1-4. Turning the motor by hand (plugs out) you should be able to feel the compression on #1. Ge5 to that point and then run a stiff wire or a skinny screwdriver into the plug hole on #1 so that it rests on top of the piston. When the wire is at its lowest point the piston is at its highest, and you should, with some looking/cleaning . . . be able to find the timing mark on the flywheel by looking up through the hole on the bottom of your torque tube, which should line up with either a very nice steel indicator or a nub cast intoon the cover in front, depending on your tractor.

From there it's pretty much like the others have said. Orient your distributor so that the rotor is pointing generally to #1, which is usually in the 1-2 o'clock position, and bolt it in. From there rotate it in until you get a spark at just that point. After that it's pretty much fine tuning by ear.

I am trying to set #1 cylinder at TDC on a Farmall A. I found the TDC (1-4) mark on the flywheel Somebody had marked it with white paint. But I still cant find the nub that the mark is supposed to be in register with. Can you describe further how to find it? How many degrees ahead of or after Bottom dead center should this mark on the flywheel be when #1 is at TDC?

Static timing is all that is needed. (assuming the distributor nis working well, and has correct advance weights and springs. The nub described below is on the side of the hole. if it is not there, use the mid point of the hole.
Static timing is TDC for the distributor. JimN

That mark will be at the most bottom position when the flywheel turns. The timing mark will be on the cover at the front of the bellhousing and the original pointer used could aslo be gone as both were used from model to model and after all these yrs who would know if yours is all original. Bottom is TDC. You are luck that its marked.

You will find out that giving it a little advance it will start maybe lots better as with the mag there is no advance for starting. Depends on the condition of your engine as the starting advance.

Somebody before you thinks like I do. I've painted that mark with a stripe on every flywheel I've been able to get to. At teh very least a dab of paint through the handhole if I could find the mark in all the grime and dark.

As for the timing mark, it is on the rear (inside) of the not-quite-half-moon cover on the front of the torque tube, under the rear of the engine. some had a very handsome steel pointer, others had just a raised nub in the casting. If yours has the latter it couldn't hurt to dab some white paint on that, too. Easy, that cover is only held on with two bolts and will slip right out. As Gene said, the mark on your flywheel will be at the bottom when the motor is at TDC.

Thanks for the reply. I was able to get the half moon cover off OK but the only thing on it that looks like a nub is a piece of thin plate running radially starting at the center to the lower edge of the cover. No markings to indicate what it is for. I will proceed trying to set #1 TDC at this mark lined up with the DC (1-4) mark on the flywheel. I am very surprised to learn the DC (1-4) is supposed to be at the bottom when the distributor rotor points to 1 oclock on the tower. Every time I try to find the end of #1 compression stroke by feeling air going out of the spark plug hole my distributor rotor ends up pointing between 7 and 8 oclock. Oddly the engine will start and run only if #1 plug wire is plugged in at the 7 oclock position on the tower instead of the 1 oclock position like the book says it should be. Other plug wires connected per firing order 1-3-4-2. Thanks again for the information.

Sounds like your BN is an old-timer. The plate you describe should have a point on it that is visible below the edge of the flywheel, and is the timing mark. They only used that on the first 35,000 or so As, Bs and BNs before changing over to the cast nub sometime in 1940. I'd never seen one until last week when we split a friend's 1940 A. If the plate doesn't reach low enough, you could use a T-square or another rig to extend a line perpendicular to center of the top edge down to the circumference and mark it with paint, too.

A couple other thoughts. If you haven't already, it's a lot easier to line up the motor if you remove all the plugs while you're doing it just so you're not fighting any rebound caused by compression.

As far as the rotor position, 1-2 o'clock is normal for #1. There are several ways to have gotten to where you are. The most common is for the distributor to have been set up with the engine at TDC on exhaust. That, and as Jim N (Ithink it as him) mentioned, setting the rotor up to point generally to #1 before installing the distributor with #1 at TDC on compression would avoid that.

It can be timed to run the way you have it now -- as long as you have spark at the right wire at the right time, it doesn't make any difference to its running where that wire connects to the cap. I'm just thinking of the next guy. ;8^) Easy fix if you want to do it now, and that is to get #1 to TDC compression, make a crayon mark on the distributor body that lines up with the #1 tower on the cap, pull the cap off so that you can see the rotor, then pull the distributor back off and turn it by hand until the rotor points to your mark, then reinstall everything.

Let us kow how you make out.

not your BN.