Homebrew electronic ignition for 651

Hdonly · Oct 2, 2017

Call me cheap. I say thrifty. I am doing an experiment on electronic ignition for my Ford 651 that I recently bought. I already have a Pertronix ignition on my Jubilee tractor. I got to thinking (1st mistake) about the cost if the module goes bad to replace it. If my experiment works out, any part that fails can be replaced for $20 or less and should be available or ordered at most any auto parts store. The Pertronix magnet assembly can be had for about $17. The GM module is about $20. The GM pickup coil is about $14. If all works out I will share the build on here. Here are some pictures of the parts I will start with. Some assembly required-haha. Might have to do some modifying, but it's all fun when working on a tractor-right?

Bob · Oct 2, 2017

I have done exactly what you propose, and it's worked GREAT.

The GM-style module is virtually indestructible vs. the fragile Pertronix, and is smart enough to shut off coil current when distributor rotation stops, vs. the original Pertronix which will happy heat itself and the coil into oblivion if the ignition is left on with the engine not running.

ONE issue, tho... the pickup coil you illustrate has it's own magnet and requires a "reluctor wheel", NOT a ring of moving magnets.

If you can't find a 4-toothed reluctor wheel you may have to remove every other tooth from one for a V-8 application.

The setup will work better with the output of the pickup coil connected one of the two possible ways to the module.

If you have access to a 'scope, IIRC, the leading edge of the pulse generated as a tooth of the reluctor wheel passes needs to be positive-going.

<img src = "https://content.speedwaymotors.com/ProductImages/547PRD10071_L_12e78b70-86e3-4127-84f6-22a6b9b1f865.jpg">

Reluctor wheel for a V-8 application

Hdonly · Oct 2, 2017

My thinking was to remove that magnet and use the Pertronix magnet wheel. I picked this pickup coil because it was the cheapest that I found. I am still looking around at different cheap parts. Using the Pertronix magnet because it would be easier than modifying the GM reluctor wheel to fit. Did you go with the GM wheel or did you use a different pickup coil?

Bob · Oct 2, 2017

I have used both Ford and MOPAR pickups/reluctors.

As to removing the large magnet on the pickup assembly and triggering with the Pertronix magnet ring, it will be interesting to see if those little magnets are strong enough to induce enough voltage into the pickup coil to trigger the module. I look forward to your progress with this!

Hdonly · Oct 2, 2017

I have read that the GM module will trigger from about .3 volt high to low signal. I will see if my idea will work. It's all part of the fun. If it doesn't trigger, then its on to some type of amplifier circuit. I am hoping to avoid any additional circuit. Want this to be so easy that anyone can put it together and save some cash.

JF in MI · Oct 2, 2017

I did something like that recently and it "sort" of worked. Great spark but ad the mechanical advance kicked in the spark jumped to a different post on the distributor cap. Wound
up using an original GM pickup and reluctor and it worked fine. What I found out later (I was converting to electronic fuel injection) was that I didn't even need the mechanical
advance in the first place because the computer does all the advancing electronically. That being the case, your setup should work with a "star shaped" reluctor.

Hdonly · Oct 3, 2017

I am going to guess that you used the five connector GM module and computer. I am using the older four connector module. The five connector module does have spark advance capability. The four connector relies on vacuum and mechanical advance,

Hdonly · Oct 17, 2017

(quoted from post at 07:34:25 10/02/17) I have used both Ford and MOPAR pickups/reluctors.

As to removing the large magnet on the pickup assembly and triggering with the Pertronix magnet ring, it will be interesting to see if those little magnets are strong enough to induce enough voltage into the pickup coil to trigger the module. I look forward to your progress with this!

Well, it sort of worked. It would trigger some, but very unreliable. I got it to run a couple of times, but it ran like it was overly rich. I think that it triggered so unreliably that the dwell was way off. The Pertronics magnet ring just doesn't seem to do the job.
Two ways to proceed. I am looking at a Yamaha trigger coil that uses a magnet on a spinning wheel. No magnet on the coil. I can get one for $9.00. I think I will try that . If it doesn't work, I guess it's back to the magnet on the GM coil with a modified GM reluctor. Stay tuned!

Bob · Oct 17, 2017

Did you try reversing the magnetic pickup wires where they connect to the module?

Another thing... the radial location of the trigger has to be so the the rotor is near a high-tension terminal when the module "fires".

If this correlation is wrong and the spark occurs when the rotor is between HT terminals it doesn't work well!

I check for this using a spare cap with an observation hole cut in it and run the distributor on my distributor machine.

How about trying the pickup coil for a "flying magnet" crankshaft ignition pickup along with you pertronix magnet ring?

<img src = "https://i.ebayimg.com/00/s/NjEyWDYxMQ==/z/3FcAAOSwWaRZser~/$_58.PNG">

ONE example of a flying magnet pickup.

Hdonly · Oct 18, 2017

I did try reversing the connections. It did not fire at all one way. Did fire the other way.
You may have something on the firing and rotor alignment. I'll have to think about how I can check that.
I have ordered a couple of pick up coils. One is for a motorcycle that used spinning magnet and I also ordered one for a crankshaft setup.
Looks like I have a few things to play with.
Thanks, Bob, for the tips and ideas.

Homebrew electronic ignition for 651

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