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

Minor update on the Pertronix-II vs Pertronix-I question:

I did finally get tired of my car devolving to a lumpy, bumpy. stinky idle at every traffic light, even with an idle of 1100 RPM in Neutral.

With the idle set that high, it would usually idle okay in Drive, but frequently, if left for over 30 to 60 seconds, it would drop below the threshold of something like 600 to 700 RPM and revert to the "firing on three cylinders" idle, and I ran out of patience.

I bought (Yes, bought. It had been over a year since this saga had begun, and they'd already given me one free Pertronix-II kit, so I didn't try to weasel another free part out of them) a new Pertronix-I kit, and I installed it a few days ago.

First, all of the parts except for the pickup unit itself are identical, so unscrewing one and screwing on the other was easy, and may have even been possible with the distributor in place (I took it out).
Second, the -II can handle more current, so it likes a lower-impedance coil (I am using a Standard Blue-Streak UC-12X, which is 1.5Ω), while the -I likes a higher impedance coil (minimum 3Ω is specified), so I had to run a couple of feet of wire so the Pertronix unit could be powered by 12v, but the coil cold be powered through the ballast resistor.

Result:

• Starts instantly (I believe it catches faster than with the Pertronix-II, which required what felt like a revolution to fire - now it catches the way it should with a nice new set of points).
• Idles smoothly as slow as I want to go. Admittedly, I didn't try to see how low I could get it, as i had to go in for dinner, but I may do that experiment in the future. At this point I have the idle just under 600 RPM in Neutral and it rolls over and over like a sewing machine.
• Idle is acceptable in Drive, but I still have a slight audible rattle, which I believe is something just a little bit loose somewhere in the front of the car. I've already changed the motor and transmission mounts, gone through the suspension and brakes, and removed, lubed, and reinstalled the driveshaft, so it's not them.
• Acceleration is smooth and power feels the same. I've got to retard the timing by about 2° from about 12° to about 10° BTDC, because I have a slight ping, using 91 octane non-ethanol gas (the only octane available in non-ethanol near me).

So, for any six-cylinder engine, if you are considering a Pertronix unit, I would recommend the -I rather than the -II.

Matt, if you still have any interest in playing with a Pertronix-II unit, I now have two of them available for you to compare.

I hope this is helpful to someone.

– Eric

Interesting. I've never tried the II and have been very happy with the I even in pretty racy engines. Thanks for your testing and story.

Lou

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Home of Slant6-powered fun machines since 1988

You're welcome.

What's supposed to be so much better about the petronix vs either stick Mopar ecu ignition or using a GMnhei module?

Speaking only for myself, and probably repeating things I wrote here earlier, on my all-original '64 Dart Slant-6 I was not trying to increase performance or reliability.
No small tweak is going to make the Leaning Tower make much more power, and with a nice new set of Blue Streak points and condenser, it started and ran great.

I had one problem, and that was an annoying unevenness / roughness at idle, especially when the 904 was in gear.
I adjusted the valves twice, checked compression, changed spark plugs, wires, cap, rotor, and coil (fancy red coil from PO was faulty), vacuum advance, cleaned and lubed advance weights and replaced advance springs, rebuilt carb, replaced fuel pump and filter (several times each, story elsewhere), but that one minor problem wouldn't go away.
I rebuilt my old SUN distributor machine and checked the distributor on it, and one out of six impulses seemed to be a degree or two off.
Similarly, on the oscilloscope, one impulse seemed a bit out of the grouping from the others.

So, I figured for less than $200 (on sale), I'd do the experiment and try an ignition that didn't rely on the distributor lobes.

This led to all of the above problems, which really kind of teed me off, but now it seems to be settled, after far more time and money than I'd intended (as usual).
The idle in gear is improved; it no longer feels like the car is going to rattle apart at traffic lights. It's not perfect, like my BMW 330 "slant-six," but it's good enough for a sixty year old economy car.

As for my own reasons for trying the Pertronix units, rather than a newer-year stock MoPar system or an HEI system:

• Less time / money / annoyance spent of part sourcing, fabrication, generally screwing around.
• No reliance on the distributor shaft lobes, as those were the suspected problem area.
• Quick and easy almost-one-step results (HA!).

Anyway, the Pertronix seems to have (finally) done what I wanted it to do, so now maybe I can go entertain myself with one of the other vehicles, or with some of the work I need to do on the house and the grounds. Its gonna be hot this week!

– Eric

The main appeal to me is that if you have a good points distributor, it's easier to install and needs fewer parts replaced. Convenience, really. And since you're changing fewer parts, it's cheaper.

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Matt Cramer
1966 Dodge Dart turbo / EFI project

You said it quicker than I did, Matt.

– Eric