Replacement ignition coil?

On this site I see replacement high performance ignition coils. My 1963 Allis D17 was not firing on 1 cylinder until the engine warmed up, so I replaced the plug wires, dist cap & rotor. It ran fine afterwards.

The ignition coil looks original. The description of the high performance coil says that you can have a larger plug gap, etc etc to increase performance with their 40,000 volt coil.

Is this something that I could expect, or should I just leave the factory coil on there?

(quoted from post at 07:25:06 05/12/11) On this site I see replacement high performance ignition coils. My 1963 Allis D17 was not firing on 1 cylinder until the engine warmed up, so I replaced the plug wires, dist cap & rotor. It ran fine afterwards.

The ignition coil looks original. The description of the high performance coil says that you can have a larger plug gap, etc etc to increase performance with their 40,000 volt coil.

Is this something that I could expect, or should I just leave the factory coil on there?

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If it ain't broke, don't fix it. That high performance coil will do nothing for your tractor unless you spend a BUNCH of money and make some serious engine modifications.

I agree with rusty you found where the problem was and fixed it so why try to mess it back up. You do know when ever you try to fix something that is not broke it will be after you fix it

Sort of depends on coil. Old VW 6 volt coils replaced with Bosch "blue"s tended to start easier in winter, could use slightly wider gaps on plugs- like .028 t0 .030 instead of the .022/.025 with no missing- sold some years back for Chicago winters, customers liked them. 12 volt latest coils assume solid state ignition triggers can be aggravating with mechanical point sets. Some of the earlier pattern high output/performance coils were larger and had more cooling capacity for hot car underhood temps when using hotrodded engines- were more a durability under extreme usage with a chrome finish for looks to justify the extra $5.00 resale price, but did work ok. You"re working now, no terminal cracks at wire ends, may as well run what you have unless more misfires and you plan to do some competition pulling instead of garden plowing. One point made earlier about the 6 volt VW- winter starting may improve with proper higher voltage capability coil. RN

High output coils generally accelerate breaker point wear and aren't needed on a slow-turning, relatively low-compression engine.

They are best used with electronic ignitions, such as the Pertronix Ignitor II or various high performance "spark boxes".

Unless you plan to also convert over to an electronic ignition switch, as long as you"re using original points and condensor system, I doubt you will notice much if any improvement using a so called HV coil, Id stay with a stock. The so called HV coil does NOT fire at any higher voltage if the compression and plug gap remain unchanged, its only that it has the ability/capacity to do so if compression is raised and/or the plug gap is increased. The stock coil will achieve sufficient voltage to arc jump a gap of 0.020 (and less) to 0.040 (and likely more) unless you raise the compression dramatically, and a gap of 0.020 to 0.030 is in the range of where youre likely at anyway.

Id look at the compression on that weak cylinder and/or the valves and their lash before I tried a whole lot of ignition improvements. If a weak cylinder is low on compression or burning excess oil (rings or valve guides/seals etc.) a hotter ignition wont cure that, it will just increase the time before the plug eventually fouls out.

The ignition is more efficient if the coil is at the correct polarity to match the tractor battery, i.e. for a Pos ground the coils + goes to distributor while for a neg ground the coils - goes to distributor, you may wanna check that

John T

I AGREE BIG TIME, Some of the high energy coils draw far more then 4 amps meaning, as you note, the points will burn out pretty quick plus even before they do they will carbon up and develop resistance and voltage drop..

FWIW John T

I converted all our tractors to the 40k volt coils and electronic ignition. I set the plug gaps at 0.040. Have spent a lot less time cleaning and setting points ever since.

The 40000 volt coil is a fable,Ignitions fire at 15 to 20000 volts.A 40000 volt coil would wreck your tractors ignition cap.I have worked with 25000 volts in color tv sets, very snappy.

Actually, the "COIL" may or may NOT be a fable, it may well have the capability to achieve 40,000 volts on its HV terminal, but youre right, most old tractors probably fire the plugs at more like 10,000 to under 20,000 volts. I guess its safe to say firing of the plugs at 40,000 volts in low compression gasoline tractor engines with plug gaps in the 0.020 to 0.040 range IS INDEED LIKELY A FABLE LOL

The actual voltage necessary to cause current to arc jump across a spark plug gap depends on THE PLUG GAP,,,,,,,,,THE COMPRESSION,,,,,,,THE MEDIUM (fuel type and mixture) IN WHICH THE ARC OCCURS and we dont have that info in front of us.

Yep the HV in those old cathode ray tv tubes could really cause some poppin n crackin n snappin OUCH LOL

Fun discussion, best wishes

John T

The only way a coil can deliver more energy is if it has greater inductance. As others have said, that increased inductance comes with a price: Shorter point life. Better to leave well enough alone.

Thanks for all the replies. I'll leave it alone.