trying to set ingnition timing on farmal m

i found out the over heating problem with the m and want to set the timing with a timing light what degreese do i set it and how many rmps what r the specs for doing compression test also thanks to every one who repleied to my earier problem i really apeate how much help u saved me thanks again brian

There are two timing marks on the crankshaft pulley and a marker on the front cover to time it with. I beieve you use the first mark, as the pully comes up in the direction that the engine turns when running, but without looking at my manual I'm not positive. Hopefuuly someone will correct me if wrong, if not I'll look the 1st chance I get tomorrow & post back.

I usually set the engine to run at just above idle when timing it.

soybeanjoe described the mark very well for static timing. The first mark on the pulley reach that indicator will have #1 at TDC. It can't hurt to pull your plug on #1 as you bring the motor around to line it up, just to make sure it's at the top of the compression stroke and not the exhaust, and that your rotor is pointing somewhere near the tower for the #1 plug wire.

With a magneto you set everything up on that mark, and there's nothing really to adjust from that point. They are at full advance (35 degrees) any time they are running.

You can use that same point for static timing a battery distributor.

For running advance on an M

0-200 rpms -- TDC
600 rpms -- 34 BTDC
800 rpms -- 40 BTDC

Those are crankshaft degrees so they need to be mesaured on the pulley. At cranking speeds, if you can keep the fuel shut off so that it doesn't start and run, you should be able to check with the existing mark, essentially just verifying the static timing that you might have done with a test light or sparking the plug or coil wire.

The trick is I'm not sure there is any mark on the pulley for either the 40 or 34 positions (I don't *think* there are), so to check your running timing with a light you'd need to find a reasonably accurate way of measuring to establish them (40* would be 1/9 of the circumference of the pulley in advance of the notch used for static timing.) If you can't make those other marks exactly, do your best to establish the 40 degree mark. Then you can at least check that your advance is working properly if a) the motor is somewhere near your new mark at 800 rpm and, b) that it retards slightly, slipping back to your imaginary 34-degree mark when you cut back to 600 rpm.

Hope that helps.

I don't know the M well enough to help with what good numbers for compression would be, which will vary according to what you have for pistons and head. All I can offer is the rule of thumb that it should be fairly consistent across all four cylinders -- if there is no more than 10% variance between your highest reading and your lowest, things are wearing evenly. From there, it's just a matter of deciding if the overall compression is up to snuff. I expect somebody will be along with numbers to help you evaluate that.

Thanks for keeping us posted.

Exzcellent post Scott. You described things much better than I ever could.

As Scott said, compression shouldn't vary more than 10% from high to low across the four cylinders. I put new rings in my '49 M a few years ago & afterwards the compression was 125#, pistons are 4" Firecraters. I put NOS 4 1/8" M&W Power Dome piston & sleeves in my SMTA winter before last & the compression on it was 145#

When we set timing i use a digital timing light that reads RPM [tach] in it.

Clip it to #1 plug wire and a power [battery].

Fire up the tractor get it warm then set it to full throtle. Turn the dist tell you get max rpm then tighten it down. DONE.

I have a dyno and this is a proven method of setting timing if a dyno isn't present.

Not knocking anyone else , Scott knows what he's talking about.
The reason we set them this way is that after 50 years ware on these old parts it's hard to use factoy spec and settings everything is sloppy and loose.

I set timing to the condition of that motor.


The best way is under load on the dyno around 1000 rpm ,this gives you everything it has.

I hope this helps everyone here is correct in the directions given.

Thanks for the advice. This is logical and makes a lot of sense from an engine wear standpoint.

I'll use it!

Scott you need to double the RPM you have listed when checking at the crankshaft. Pays to see what parts are in the advance units and shape before setting distributor to full advance at crank with a light and ignoring static timing. Lots of M and other had fire crater piston sets installed along the way and the had parts to change the rate and total on advance. Even parts to change magnetos were furnished for some kits. I guess they still sell what I call set back timing lights, haven't looked in years mine still works. You can adjust it to read advance on the TDC timing marks, say when the engine is wide open and at 40 degrees advance the light can be adjusted to light up at the static timming mark. How time flies that light is probably a antique from 40 years ago, back in hot roding days. If I misunderstood your answer, sorry.

Good catch! And no apology needed. You read it right. I remembered to double the advance numbers but not the rpms from the chart.

Brian, those should read

0-400 rpms -- TDC (that's about as low as you can hope for it to idle)
1200 rpms -- 34 BTDC
1600 rpms -- 40 BTDC (which is pretty much the wide open running James referred to when setting timing)

And D Slater's note about modification over the years might explain any variance you find from those numbers, too, when you get it running right, as well as the slop from wear that James cited.

Sorry, Brian, for the confusion. But we're all still on the same page.