KJL

I have noticed a progressing corrosion inside my distributor. I have an MSD distributor with a programmable 6AL ignition system. I popped the cap today and was really surprised at much more corrosion there was on all the metal and aluminum components. The car does not get driven much so it seams moisture just can't escape from inside. I have another cap with a "window" cut in it that use for rotor phasing. I may just switch to that one so at least there will be more air that is allowed to circulate inside. Any suggestions? How common is this? This is the first distributor I seem to have had this problem with. Could crank case gases be making their way up into the cap? I am not running a PCV valve but do have 2 breathers, one in each valve cover. I will post some pictures.

stingr69

Positive crankcase ventilation pulls out water vapor from the engine. Why not start there? Having passive "vents" is not positive removal of water vapor. PCV is a good system to keep. It goes inactive at wide open throttle anyway so there is no downside.

carriljc

It's nasty crap. Never had any other distributor corrode like that. here is some info on that. I've cleaned mine several times and the last time I used POR-15 and it seems to help keep it at bay..... I must say that it's never failed me but it is still b.s. that they put out such stuff.

https://www.corvetteforum.com/forums...i-replace.html

drwet

I run an MSD Pro-Billet HEI and I had the same issue a couple of years back,, The engine started to ping badly and I traced the problem to a seized mechanical advance mechanism. The inside of the distributor was much more corroded than I would have expected on a car that spends its life in a heated garage.
The solution is pretty simple. Pull the distributor, clean everything up and put it all back together. Not a big deal but now inspecting the inside of the distributor is part of my annual maintenance routine.

KJL

Running a PCV is a bit of a problem for me. I need all the vacuum I can get at idle. I may give it another try once I get my carb dialed back in. I cleaned up the distributor per a thread I saw with recommendations from an MSD tech that said to lightly coat the paddles with lacquer. I used polyurethane. I also coated some other components that were rusting after cleaning them up. I also drilled four 1/4 inch holes about half way up the sides of the cap at 90 degrees to each other. I think that should help a lot. Other than that everything else was in perfect condition.

Factoid

What does a pcv valve or system have to do with this issue???

This has been an issue with MSD distributors for a long time and I’m surprised for the prices they charge it has not been addressed. Interestingly, Porsche experienced a similar issue in the 90’s when they introduced the 3.6L twin plug engine with a dual distributor. They issued a service bulletin and parts kit to vent the distributor caps which effectively fixed the issue.

KJL

nothing really.

7T1vette

Is your distributor made by GM or some aftermarket brand? Bare metal parts will rust/corrode. Parts require plating to prevent corrosion. "New" aftermarket stuff looks 'shiny'. Don't know how long they stay that way............

KJL

It is an MSD unit.

BKarol

This has been an issue with MSD distributors for a long time and I’m surprised for the prices they charge it has not been addressed. Interestingly, Porsche experienced a similar issue in the 90’s when they introduced the 3.6L twin plug engine with a dual distributor. They issued a service bulletin and parts kit to vent the distributor caps which effectively fixed the issue.[/QUOTE]


Just google "MSD rust inside distributor" and you will get a number of hits. Remedies have been from drilling holes, clean every year, to removing the cap after you get home from a drive.
Need to stay on top of it.

vivasantana

I can't see a PCV having anything to do with it either.
My cap & base were rusted as well, burnt the crap out of a few cap terminals & ran horrible.
I did replace with another MSD, supposedly it has a rust inhibitor coating.

It's on my 74 302 Capri, only driven once a week or so.
I pull the cap off after every drive, it won't corrode again.

HeadsU.P.

I think how this theory started about the oil in a dizzy was from a few yrs back. A poster said the internals of a HEI were oily and causing erratic running.
The story went on to say there was none or little evacuation of the crankcase, no PCV valve, breather, etc. It seems high crankcase pressure might force oil or maybe it wicked up into the distributor housing.
I don't know if that could happen or not.

Also, a quick search of dizzy caps on Summit shows some had brass terminals, some had aluminum terminals. H-m-m-m-m-m-m-m-?
Some were $19.95 and some were $38. Again, h-m-m-m-m-m-m-m-m-m-

7T1vette

Un-plated bare metal..... Just 'cause you paid a lot of $$$ for a brand name product doesn't assure that the product is made well.

Factoid

I remember reading the Porsche service bulletin that talked about ozone building up inside the cap and causing significant corrosion. I swore by MSD for decades, but always had this corrosion issue (even on very well ventilated engine blocks). I always wondered why oem distributors didn’t seem to suffer from the problem. It then dawned on me that under 3000rpm the MSD fires multiple times and the spark energy is significantly higher than stock. All the more reason for MSD to use stainless steel or ensure good corrosion protection.



This is a 3.6 dual plug air cooled 911 engine from a 1995 911. You can see the strange dual distributor arrangement and the vent tubes that were installed in the distributors. It is the dirty clear tube passing between the two coils and the distributor. It is plumbed into the engine cooling shroud that creates a suction due to the large fan and plenum that covers the engine.

I replaced it for a more vintage look with a single 12 plug distributor.

Here installed in my 1975 wide body. My point to all of this is that some form of ventilation should help!

KJL

i think if you had a lot of blow by and poor ventilation coupled with a worn out dizzy, you could get some gasses making their way up into the housing. For me me most of the corrosion was on the paddles. Some on the magnet that the pickup is mounted to. The brass terminals in the cap had a little crust on them as did the rotor. Thing to keep in mind that this is after relatively few miles since I cleaned it up last time. I am interested to see how the holes and coating the parts with urethane will work out. Venting will also help reduce the likelihood of arcing due to ionization. I don’t know if I would go so far as to pull the cap after every drive but probably a good idea to check periodically. Maybe at every oil change.

OldCarBum

Order an MSD marine distributor cap and install it.
All marine distributor caps allow moisture to escape while sealing out fuel vapors through a one way valve built into the distributor cap.
It’s small and unless you know what it is, you wouldn’t know it’s not an automotive cap.

carriljc

Doesn't matter. I replaced my cap with the recommended cap and it didn't make a ****. It's crappy material. The only thing that has minimized it is coating with POR-15. I have an old Mallory distributor that I used for 10 years and that has been sitting in the same garage as the car for the last several decades and it still looks brandy-new. It's crappy material.

HeadsU.P.

The thought of drilling ventilation holes in a car part (cap) that is suppose to be somewhat water proof just doesn't sound right.
No thanks.

There was a reason the old "Points & Condenser" IGN style caps had a closable window on the side of the cap.
To keep shet out.

theandies

I have an MSD pro billet and have zero corrosion. It's been on the car since 2001 when I installed my ZZ4. I have changed the cap and rotor a few times since then. Everything always looks good under the cap. Maybe I just have a good one or just lucky. Now I need to go look at it because I haven't messed with my timing or anything for a few years now.

KJL

where do you live? Climate would have an impact on it.