-   Jeep CJ Forum (
-   -   Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8 (

Matt1981CJ7 06-28-2018 03:48 AM

Personally, I'd ditch the points, and stick a quality HEI or CDI system in there.

Many guys prefer the HEI because of the easy one-wire install. You can eliminate the existing coil and any old ignition modules, because those things are built right into the HEI distributor. There is a minor gear engagement issue with HEI, due to its design. It doesn't engage the cam gear as fully as a stock distributor does. Jeephammer claimed this could cause premature gear wear, but a ton of guys run HEIs with no problems.

I prefer the separate components of a CDI system and a distributor that is designed specifically for my engine. My system is all MSD products.

The HEI vs CDI debate will probably rage forever. The truth is, you probably wouldn't notice a lick of difference in performance between the two, and they're both a big upgrade over points.


PottsyCJ5 06-28-2018 04:18 AM

Thanks Mat and John. Iíll look into how to adjust to the dwell for now, and also start going down the rabbit hole of researching what ignition system I want to go with now that I know what I am starting off with.

Iíve heard great things about MSD. The stuff with the cam gears on the HEI systems scare me to be honest though. The petronix is a little pricey but not bad for a single unit. The earlier models are cheaper now that the petronix III is out it seems, and I might be fine with the Ignitor II series. At some point down the road I may just try that route for simplicity sake for myself, and see how it goes. Iíve bought enough meters for now and donít feel like investing in a dwell meter if Iím ultimately going to want to ditch the points anyway.

Thanks a lot fellas.

Sent from my iPhone using Tapatalk

PottsyCJ5 06-28-2018 10:44 AM

Sorry, couple more questions... lookin at these petronix systems is a little daunting having never done any ignition work before. I am trying to price out the petronix and I am not sure what I need. Since the PO swapped the stock prestolite distributor for the AC Delco Points distributor, is this the correct petronix to buy if I want to convert my current dist over to electronic?

PerTronix 91281 Ignitor II Adaptive Dwell Control for Ford 8 Cylinder

Iím not sure I need the Ignitor III though I am considering going that route to get the multi-spark technology. This isnít a performance rig, I just want to get all the power I can out of my 304 and switch to a setup that requires les maintenance (and is fairly simple to install).

Also, when I adjust my timing the distributor was REALLY hard to turn. Is that common or should I be concerned? When Iíve watched videos of people timing their engines it looks pretty effortless to turn the dizzy and mine took a pair of vice grips to get to turn. Because of that I was considering switching out the whole distributor with a petronix dizzy with the igniter ignition built in, BUT one summit it mentioned for AMC engines itís recommended to swap out the cam gear when changing to their distributor. That is more involved than I am trying to get at this stage in my Jeep journey.

Sounds like I should upgrade my spark plug wires as well, which I was planning on doing anyway.

Sent from my iPhone using Tapatalk

Matt1981CJ7 06-28-2018 10:50 AM

Did you loosen the hold-down bracket at the bottom of the distributor before attempting to change timing?

Sorry, I can't help you with your Petronix questions, as I've never used one. I view it as a bit of a bandaid solution, anyway.


PottsyCJ5 06-28-2018 10:56 AM

I did loosen the hold down clamp, Matt. Thanks.

Sent from my iPhone using Tapatalk

Matt1981CJ7 06-28-2018 11:09 AM

Then something is amiss with your distributor. With the hold down bracket loose, it should turn easily.

I'd find TDC of #1 cylinder, then pull the distributor. Hopefully the problem is internal to the distributer and not a gear mesh problem.

Good luck,


PottsyCJ5 06-28-2018 01:42 PM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
Ugh, yeah it was seriously difficult to turn. Everything seems to be functioning fine but it was scary hard to turn.

The whole thing should turn correct? as in not something inside the shaft is what turns, but the entire assembly spins? I literally had to put vice grips on it and pull with all my night to budge it. I was able to get the timing adjusted 5 degrees eventually by turning, but I almost gave up for fear I was breaking something when it budged enough to move it. I figured there was just rust or crud on the shaft, but didnít consider the gears.

Sent from my iPhone using Tapatalk

Matt1981CJ7 06-28-2018 02:49 PM

Yes, the whole distributer should turn quite easily.

Hopefully the distributor shaft bore is just corroded, making it difficult to turn. You'll know when you pull the distributor out. You should be able to spin the distributor shaft/gear with your fingers easily.


PottsyCJ5 06-28-2018 03:28 PM

Thanks bud.

Sent from my iPhone using Tapatalk

RedNeckCorvette 06-28-2018 04:10 PM

I have had a distributor shaft lock up in the past on a 400 Ford. I feed it penetrating solvent for several weeks wile hitting it some place on the pot metal with a light plastic hammer. Tap it around, up and down to let the fluid do it's thing. Sooner or later it will give, most of the time.

If you change the distributor over to HEI or what ever else? Take the gear off the bottom of your old distributor and put it on the new one. Most of the time this requires you to push out one retainer pin on each gear, then just switch the gears. The old goes on the new distributor and now it matches the wear pattern on the cam exactly. Lay them side by side and check the overall length. If ever, rarely [I have never seen it] there may be a difference. Nothing to it really.


PottsyCJ5 06-29-2018 07:08 AM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
Hey thanks man, that sounds like solid advice. I have been hesitant to touch the dist. after getting it timed for this reason. If I can reuse the current distributors gear and not have to replace the cam gear, I may considering going for a petronix like distributor instead of just the module.

Swapping the gears between distributors wonít change the behavior of the new distributor? Like screw up the timing or anything? I mean I know Iíll have to retime it, Iím talking about the new one spinning at a different rate than designed if the gears donít have the same profile or whatever.

I know I read some of the HEI dizzys out there use a hardened gear which chews up the cam gear too, so this seems like a good option for peace of mind to avoid that.

Sent from my iPhone using Tapatalk

Matt1981CJ7 06-29-2018 07:58 AM


Yes, you have to be careful about mismatching certain HEI distributors that have a gear that is hardened more than the factory cam gear. This is especially the case with AMC V8s because they have a detachable cam gear that is softer than the cam itself. On the I6 engine, the cam gear is machined into the cam, which is already hardened, so it's less of an issue.

As long as you have a matching set of gears suited for your engine, it won't affect the function of the distributor. The distributor gear spins only as fast as the cam gear makes it spin.

Hope this helps,


PottsyCJ5 06-29-2018 07:01 PM

That does help, Matt. Thank you. Itís funny, I started this thread just to make sure I could disconnect my ICM, and by the way of it learned enough about my ignition to convince me to swap out my points and go electronic. Man working on this jeep is addicting.

Sent from my iPhone using Tapatalk

John Strenk 07-01-2018 06:30 PM

There is a special kine of therapy for that kind of addiction. It's called B.R.O.K.E.

Matt1981CJ7 07-01-2018 09:09 PM


Originally Posted by John Strenk (Post 40265669)
There is a special kine of therapy for that kind of addiction. It's called B.R.O.K.E.

LOL. The Warden said she'd Nutter me if I spent any more on mine. >:)


The time now is 04:04 PM.

Powered by vBulletin Version 3.8.8
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.