Pertronix Distributor Cap & Rotor

[tkb289]

Had a problem recently where my ERA FIA was not running very well, turned out to be the distributor cap and rotor.

Here is what happened. Running a 302 with a Pertronix flame thrower distributor and Pertronix coil and now have about 3,800 miles on the motor. At around 3,700 miles the motor started running a bit rough at lower RPMs, but rev it up a bit and it ran great. It steadily got worse after about 100 miles and got to the point where the motor would hardly run. I was actually headed lippy's house to see his new 427 ERA (BTW ... it's a beauty) and I just barely made it. After a few minutes of looking for something obvious, loose wires and the like, I pulled the distributor cap. What I found (and should have taken a photo) was on the center contact of the rotor, some thick black material, almost like oil but just in that one area. I wiped it off, put the cap back on and the motor started right up and ran petty well.

I have installed a new distributor cap and rotor and went for a short drive, the motor runs a lot better now and is back to the way is was before this happened. I should add that overall I have been happy with the performance and look of the Pertronix distributor and coil setup.


I have some observations and questions for you guys, photos are below.

- The underside of the cap is fairly clean and very dry, no evidence of moisture. However, there is some corrosion or oxidation on the contacts. The tip of the rotor is not too bad, but the center contact has a pit (and had that black goop on it).

- When I removed the rotor, I noticed that the springs for the weights are rusty, along with part the base plate. The weights move freely and there is a bit of grease here and there to help them move.


Questions …

Around 3,800 miles seems a bit quick (at least to me) for the cap and rotor to have issues like this.

- Is this expected for these parts?

- Has anyone else had a similar experience?

- What would cause the thick black material on the rotor center contact? My guess is probably the contact point from the cap wearing away?

- What would cause the 'corrosion' on the contacts or is that just arcing?

- The rusty springs and rust inside the distributor, anyone else seen this?

- Any recommendations as to what to put on the rust areas & best way to clean and lube, or just leave it alone?

- Comments or suggestions?

Thanks !!!


tkb

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Old rotor and new rotor



Old cap



New cap



Rust on springs



Other rust areas

[jhirasak]

TKB,

From looking at the photos that you posted, it appears that you have had significant moisture condensation inside of your distributor in the past. This can lead to electrically conductive paths in the cap which sends some of the spark to other cylinders or to ground, hence the missfire and rough running.

The usual cause of moisture condensation inside the distributor is washing your engine while it is hot and any steam that has gotten into the distributor naturally condenses on the cooler cap interior surfaces. The best way to avoid this situation is to remove your distributor cap after you have washed and cleaned your engine and let it air dry for a while before reinstalling your cap. If you need to drive your car soon after you have washed the engine, then check the condition of the cap the following day and wipe any condensed moisture from inside the cap. This should prevent the situation that you have experienced from causing you problems in the future.

John

[Frank Messina]

I agree with John in that moisture was somehow introduced that lead to corrosion and arcing. If you haven't done it already, remove the springs and weights and clean everything off thoroughly to remove all rust and apply Boeshield. They make a cleaner and a rust inhibitor that is perfect for this.

Frank

[LMH]

It looks like a lot of arcing on the contact posts inside the cap. Never seen one quite that severe.
Larry

[Barnsnake]

Ozone is also a major contributor to corrosion inside a distributor with high energy ignition systems. In combination with atmospheric moisture it can make things look like they've been immersed in salt water. Vented caps or distributors with vents help reduce ozone buildup.
Poor rotor phasing may also be a contributor to excessive ozone generation, due to longer sparks inside the cap.

[tkb289]

Thanks guys for the comments and suggestions.

It does look like there has been some significant moisture under the cap at some point, and or lots of Ozone? I can say that the motor has never been hosed down or the car ever driven in the rain. It’s not even very humid where I live, so that pretty much leaves the distributor being manufactured or stored in a humid environment or the effects of Ozone or both?

I’ll take the metal bits apart and clean them up, then keep an eye on things from time to time. I have put over 50 miles on the car since the new cap and rotor were installed, and it’s never run better.

[tkb289]

Originally Posted by Barnsnake

Ozone is also a major contributor to corrosion inside a distributor with high energy ignition systems. In combination with atmospheric moisture it can make things look like they've been immersed in salt water. Vented caps or distributors with vents help reduce ozone buildup.
Poor rotor phasing may also be a contributor to excessive ozone generation, due to longer sparks inside the cap.

Barnsnake,

I think you are onto something …

I decided to look through some of my photos and found this one from the motor install.






Nice and clean looking distributor with no surface rust. I had forgotten that I took the distributor cap off, the power of pictures. I am sure that if there was the corrosion under the cap at that time, I would have noticed it. The motor at that point only had the dyno run time on it.

Since I know there has been no water from hosing down the motor nor from driving in the rain, the Ozone theory causing the corrosion is looking very likely indeed. I assume the distributor caps are not vented so as to not to introduce dirt moisture under the cap.

Barnsnake called it … has anyone else seen this type of issue?

Has anyone drilled vent holes into the cap? If so, how big, how many & where and did it work?

[tkb289]

I have done some more research with more to follow. I got some great advice from a good friend. He said do not drill any holes in the distributor cap, as a spark could come through the hole and ignite vapors under the hood, which would not be good.

Evidently, in a lot of cases vented caps from a manufacturer come with screens or other devices to keep the electricity confined to under the distributor cap.

There is also the possibility of vapor (blow by) from the motor coming up into the distributor, but I am running a fully functional PCV valve setup and there was no oily reside under the cap, so in this case I do not think that is the issue.

Could be a manufacturing tolerance stack up, that resulted in a wider gap than usual, between the rotor tip and the contact points inside the distributor cap. This could explain the amount of arcing that seems to have occurred.