After 50,000 miles and about 20 years, the Pertronix electronic ignition system (kit 1867A I think) is still working like new on my 61' Plymouth Valiant.

Peter.

Glad to hear it, Peter. I have a similar longevity on mine, and still runnin'.

Lou

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Home of Slant6-powered fun machines since 1988

I have not had my Pertronix unit very long at all, and have not used them before this, but I can add this information:

I have no problem in general with points ignition systems, especially on stock American engines. I used them for many years without any problems, and I've got enough cars that I don't drive any one of them, including my '64 Dart, enough for the maintenance to be a problem. In my case, I had a definite unevenness in the idle, which disappeared at running speeds, but which was very annoying, and which corresponded to a slight but definite uneven spacing of the spark interval of one cylinder on both my distributor machine and my oscilloscope. I figured that if I had a badly machined distributor lobe, installing an electronic ignition unit would cure it, and installed the Pertronix one year ago mostly as an experiment to see whether I was right.

I believe that both Lou and Peter probably installed the Pertronix-I units.
I installed a Pertronix-II unit.
I chose the -II because of it's "auto shut-off" feature. I read that the -I units do not shut off if the ignition is on and the engine is stopped, and that, in at least some cases, leaving the ignition switch on for as little as 30 seconds with the engine not running has caused the units to burn up. Since my wife drives the car sometimes, and she can "occasionally" be a bit... absent-minded, I felt that it was wise to insure against my having to drop everything, jump in my car, and drive to wherever she was stuck to install an emergency set of points.

What I discovered was this:
The Pertronix-II unit has a known flaw that is most prominent on 6-cylinder engines, that causes a horrendous idle by, apparently, shutting down half of the cylinders below about 500-600 RPM.
This appears to be due to dropping below a certain "pulses per second" threshold, which is why it's seldom encountered on 8s.
I had a very long conversation with a Pertronix rep, who brought in a technical expert, who admitted that this is a known problem that they have tried to fix, but were never able to, over the 10-20 year life of this product, because they can't figure out why it does it.
I assume that's just code for "we don't care enough to try," but still it was an interesting thing for them to say.

With the Pertronix-II, when the idle drops below a certain speed, the unit appears to instantly switch to a different "mode," visible on the oscilloscope as alternating waves of a different appearance, and the engine runs like it's on 3 cylinders, which it apparently is (including emitting eye-wateringly rich exhaust, like a "dieseling" gas engine). It is impossible to figure out the exact speed at which this happens because the instant it happens, the tach jumps UP several hundred RPMs, and stays there, even though the engine is turning slower.
Increasing the engine speed above the same threshold brings it back to the "normal mode" just as instantly, like turning a switch, and the tach jumps back down.

I ASSume that there is something about this low-RPM mode that is supposed to help with starting, but I have no idea what.

By chance, the first unit Pertronix sent me was manufactured incorrectly (pickup only riveted in one place, instead of two), so they sent me another, so I had two. I found this problem with the second unit, so I went back and fixed the first unit and tried that one, and it did the same thing, but at about a 50 RPM lower threshold, so they are all different, which was also something the rep told me on the phone.

The choice the Pertronix rep gave me on the phone was that I could swap my -II unit for a -I unit (and lose the "auto turn-off" feature) or I could increase my idle. The car definitely runs better, smoother, and maybe a bit quicker, with the Pertronix unit, so I kept it, and incrementally increased my idle to where it almost never does it. This did not require raising the idle enough to make the car "jump" when shifting the 904 into gear, but it's definitely a bit high, though only a car guy would notice.

So, that's my review of the Pertronix-II. I like the way it starts and drives, but I don't like the way it sits at traffic lights.
If there are any electrical engineers out there who would like to borrow my other unit to experiment with, let me know.

– Eric

Hi Eric,

Thanks a bunch for that detailed account of the P-II running condition and flaw. I have left my ignition on occasionally with my P-I and have not had a burnout. Also, when I recently ordered a new Pertronix for a "backup" dist, I got the P-I because I did not see the reason for features advertised for the P-II. Guess I dodged a bullet there?

Thanks again and all the best,
Lou

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Home of Slant6-powered fun machines since 1988

Yeah, From the comments I saw across a variety of makes, the Pertronix-I has an excellent reputation for durability.
I've got one in a Ford 9N tractor that a guy gave me (I'd have stuck with points, but he had a Better Idea™ and threw out the points parts), and it seems to work well.

As time goes on, I'm thinking about going to the Pertronix-I, but, really, the -II is working fine, as long as I don't need the engine to tick over like a sewing machine.

– Eric

Well, I'm actually a mechanical engineer who sometimes masquerades as an EE, but I'd be interested in testing this out. It would take me a while before I can have a look as I have a few bigger fish to fry, but this sounds like an interesting problem.

And, if PerTronix isn't interested in fixing this, a tempting target...

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Matt Cramer
1966 Dodge Dart turbo / EFI project

PM me.

I've got photos and video of the CRT oscilloscope traces.

If you have access to a distributor machine, it would be a trivial matter to set up a distributor with the unit installed, and monitor the output with a modern computerized bench oscilloscope. I'm sure there are a lot of frequencies filtered out by my 1978-ish SUN machine. (I do have a late-'90s computerized HP portable scope, but I did not try to check it with that).

– Eric