New to me Farmall M and a question

Farmall M, Super M, 400, 450 & 560 Tractors, 1939-1963
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Sterff89
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New to me Farmall M and a question

Postby Sterff89 » Sun Dec 19, 2021 8:08 pm

Just picked up this 1950 Farmall M at auction yesterday. It has a few issues but, is worth fixing up in my opinion. It has been converted to 12 volt and has an alternator. Id like to convert this to electronic ignition as I have on some of my other Farmalls. This would be my first one with a 12 volt system though and the tractor has a resistor wired up to the coil. When I replace the coil do I need to reuse the resistor and what coil do I look for? So far the repair list is: front tire needs a tube, rear tires are loaded and I'd like to eliminate calcium chloride, carb is clogged up and needs rebuilt, ignition system rebuild, oil pressure gauge and valve cover are leaking, radiator cap is broken, seat needs rebuilt, also the belt pulley is leaking pretty bad. Im sure Ill find more things to fix but, that's half the fun.
farmall m.jpg

staninlowerAL
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Re: New to me Farmall M and a question

Postby staninlowerAL » Sun Dec 19, 2021 9:39 pm

You can use a 12v coil with internal resistor and eliminate the existing external resistor at the coil.

Gary Dotson
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Re: New to me Farmall M and a question

Postby Gary Dotson » Mon Dec 20, 2021 8:41 am

If the existing coil is okay, I wouldn’t replace it. Stock coils work quite well with Pertronix. If you decide to do that, be sure to connect the hot lead, to the Pertronix, to the switch side of the resister, not the coil. Your list of repairs matches, almost exactly, to the repairs I made to the neighbors Super M, everything but the belt pulley seal. Adjust the valves, while the cover is off.

Sterff89
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Zip Code: 17512

Re: New to me Farmall M and a question

Postby Sterff89 » Mon Dec 20, 2021 7:32 pm

Ok, so I got the hood off today and a 25 ohm ballast is mounted on the alternator. I saw this yesterday but, wasn't sure what I was looking at with the hood on. Also it appears the tension of the belt is holding the alternator tight against the valve cover....? So if I use a pertronix flame-thrower coil I can remove this ballast? The coil on the tractor is leaking and mounted with zip ties and strapping so I want to replace it. Also Im going to have to rework the alternator bracket.
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Jim Becker
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Re: New to me Farmall M and a question

Postby Jim Becker » Mon Dec 20, 2021 11:25 pm

Picture makes it look like that resistor is in the exciter circuit of the alternator rather than the primary feed to the coil. If it is part of the charging circuit, you will still need it.

By the way, an ignition resistor should be around 2 ohms. An exciter resistor should be around 10. I suppose 25 might work okay in the exciter circuit.

Gary Dotson
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Tractors Owned: 48 Cub Diesel (Cubota)
53 Cockshutt 20 restored (Shooter)
52 Cockshutt 20 unrestored
47 Leader "B" (Herckie)
49 Leader "D" (Princess)
49 Leader "D" very rough
48 Leader "D" unrestored
Kubota B6200E
Kubota B6200HST
Kubota B8200HST-D
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Location: OH West Mansfield

Re: New to me Farmall M and a question

Postby Gary Dotson » Tue Dec 21, 2021 8:47 am

As Jim said, that resister is for the alternator, not the ignition system. There’s no knowing what your coil is, without testing it. Approx. 1.5 ohm = 6 volt or 12 volt external resister, approx. 3 ohm = 12 volt internal resister. The instructions for the Pertronix gives the ohm requirements and diagrams for hookup either with or without the resister. Be aware that the Flamethrower coil may not meet their ohm requirement for a 4 cyl. Engine, it’s made for 8 cyl. Engines where lower coil ohms are more tolerable. (An issue of dwell time). It has long been my preference to avoid getting too aggressive with the “hot” coils. The Pertronix will make a big difference, even with a stock coil, it just has to be a good one.

Sterff89
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Zip Code: 17512

Re: New to me Farmall M and a question

Postby Sterff89 » Thu Dec 23, 2021 7:15 pm

I think I have it figured out now but, I have not tried to start it because the carb is off. I did have to make a bracket to mount the coil though. I hooked up the wire from the alternator going to the + side of the coil same as it was before.

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Sterff89
Posts: 18
Joined: Wed Oct 20, 2021 5:21 pm
Zip Code: 17512

Re: New to me Farmall M and a question

Postby Sterff89 » Mon Dec 27, 2021 4:42 pm

So I got it running after rebuilding the carburetor and it is charging. It does start nicely but, I do have to make some adjustments to get it to run better. I drove it around for awhile and everything seems to work as far as clutch, brakes, and it goes in all gears. It did not like 5th gear and the front end seems to shimmy pretty bad. After parking it I drained the oil. There was a fair amount of water in the bottom of the pan. I took off the oil pan and valve cover and both were coated with white sludge. The coolant is pretty full so I think it is condensation? With the oil pan off the inside of the engine is pretty clean.
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