Petronix Electronic Ignition Upgrade - 6V or 12V Coil

Hi,

I have a '72 JD 3020 gaser with 12V negative ground. I have purchased a Petronix Ignitor II electronic ignition kit and I'd like an opinion of what coil is correct for this application. On yesterday's tractor here...
https://www.yesterdaystractors.com/45011_Coil-Ultra-High-Performance-Black-Oil-Filled_32602.htm
...they note this coil is for use on 6V stock system or 12V electronic ignition upgrade.
Can anyone advise if this is correct for my application? Note that resistance on the stock coil is 1.8 Ohms and the new 6V coil is 0.9 Ohms.
This link on their partner company tractorpartsasap makes me question the application:
https://www.tractorpartsasap.com/electronic-ignition-coil-6-volt-new-ford-108304.html

Cheers,
Scott

(quoted from post at 23:04:09 10/16/22) Hi,

I have a '72 JD 3020 gaser with 12V negative ground. I have purchased a Petronix Ignitor II electronic ignition kit and I'd like an opinion of what coil is correct for this application. On yesterday's tractor here...
https://www.yesterdaystractors.com/45011_Coil-Ultra-High-Performance-Black-Oil-Filled_32602.htm
...they note this coil is for use on 6V stock system or 12V electronic ignition upgrade.
Can anyone advise if this is correct for my application? Note that resistance on the stock coil is 1.8 Ohms and the new 6V coil is 0.9 Ohms.
This link on their partner company tractorpartsasap makes me question the application:
https://www.tractorpartsasap.com/electronic-ignition-coil-6-volt-new-ford-108304.html

Cheers,
Scott

Click to expand...

ou should get Pertronix to tell you what coil to use with their module, but I will say that what you want is about 4 amperes steady on coil current and for a 12v system, that is a primary coil resistance of about 3 Ohms. 0.6 Ohms will likely destroy the unit.

From Pertronix website:

"The Ignitor II ignition can be used in conjunction with most ignition coils rated
at 0.45 ohms or greater. For optimum performance purchase and install the
Flamethrower II high performance coil."

If your original coil and points set up was working, there is no need to replace the coil.

If you want to replace the coil, go back with one as close to the original as possible. Having a coil with that low resistance says there is probably a resistor or resistor wire in the harness. Like JMOR said, 4 amps or 3 ohms resistance, nut the 3 ohms must include the resistor if equipped.

There is no advantage to using a 'flame thrower' coil on a tractor engine!

One other thing you can check, ignition on, engine off, ground the - terminal of the coil, check the voltage on the + terminal. If it is near battery voltage, it needs a 3 ohm coil. If it is near 6 volts, it needs a 1.5 ohm coil.

Work quickly so not to overheat the coil during the test.

Speaking of heat, a correct coil will run about the same temperature as the surrounding components. If it is too hot to touch under normal running conditions, it is not right.

My FIRST recommendation is LISTEN TO WHAT PERTRONIX SAYS TO USE versus myself or others in order to not void the warranty (IF applicable). HOWEVER that being said, as an engineer its my opinion the elec switch does the same as points did IE it switches coil current ON and OFF AND SO LONG AS IT CAN HANDLE THE CURRENT BEING SWITCHED (which it surely does) OTHER SUITABLE COILS (iffffffff correct resistance) SHOULD STILL WORK FINE.

One disadvantage of points is if current is exceeded they can burn prematurely while if an elec switch is used AND IT HAS ADEQUATE CURRENT RATING THE COIL DRAWS theres little to no degradation as compared to mechanical point contacts.

Another opinion is unlike high compression racing engines where high energy ignition is required, an old low compression low RPM tractor engine benefits far less (if any at all) from a high energy ignitor coil versus an old stock coil.

BOTTOM LINE 1 follow Pertronix (IFFFFff necesary to void any warranty ?? ask them not me) but if you use a stock coil PROVIDED ITS RESISTACNE DOESNT CAUSE MORE CURRENT THAN THE SWITCH IS RATED FOR I doubt in an old low compression tractor engine theres much difference THATS JUST ME AND MY GUESS

Not having the specs Id GUESS the current rating of the switch IS PLENTY ADEQUATE for a proper coil stock or pertronix

BOTTOM LINE 2 DO NOT ue a coil that causes more current draw than the switch is rated for

OPINION the high energy coil recommended by Pertronix may not cause much if any noticeable improvement in an old tractor while a proper resistance stock coil will still work as the switches current rating isnt isn't exceeded. IE I dont think a high energy coil is required at all but when choosing a coil make sure it doesn't draw more current then allowed by the switch.

OPINION I would use a 12 volt coil (Pertronix or stock) NOTTTTTTTT a 6 volt coil plus an external series voltage dropping (12 to 6) ballast resistor.

Your tractor your choice not mine

John T

When I installed a Pertronix uint on my CA Allis I purchased their coil as well to be sure I had the correct coil.

I installed a Petronix ignition on my gas 4020 in 2000, I used the stock factory coil, still works fine. I install the sparkplug inserts later and plugs last for a couple of years.

I wanted to post an update after speaking with Petronix. Although my coil isn't stamped as the Flamethrower II they said the resistance matches and was there recommendation in order to take advantage of the larger plug gap and bigger spark.

I realize many think this modifiation is silly on an old tractor, but I will tell you it runs completely different with this system.

Recommended IMHO.

(quoted from post at 13:19:51 11/02/22)
I wanted to post an update after speaking with Petronix. Although my coil isn't stamped as the Flamethrower II they said the resistance matches and was there recommendation in order to take advantage of the larger plug gap and bigger spark.

I realize many think this modifiation is silly on an old tractor, but I will tell you it runs completely different with this system.

Recommended IMHO.

Click to expand...

ood reason for asking the maker. Pertronix isn't Pertronix as they say.....Pertronix Ignitor and Pertronix Ignitor-II are not the same critters & coil used with each can be different.

Very important comment yes, and so everyone is clear I installed the high performance Ignitor II of version electronic ignition kit which is mandatory if you want to use the lower resistance Flame Thrower II coil ~0.9 Ohms.