Failure #2 of MSD distributor cap on FE ???

[decooney]

UPDATE: AFTER THE REAL TEST DRIVE after REPLACEMENT of my faulty MSD CAP.

I would have never imagined that a change of my (second) 1.5 year old failing MSD distributor cap would have made such a bid difference as it turned out today. My car has not run this good as far as I can remember. I could feel the impact of every cylinder in the seat of my pants. What a lucky find. Runs great now. Still kinda shocked.

On a related note, I met with the NorCal Cobras group for our monthly and another guy comments about his car missing lately too; so the group of us standing there looks at each other and says "hey, let's go pull that MSD distributor cap too and see"... well all be darn, sure enough, same exact problem. The little carbon contact in the center was just like mine, totally disintegrated, gone, dished in, with bits of ash all inside the cap clinging to the contacts. DISINTEGRATED. Indexed or not, we need to figure out what the real root cause is here; otherwise these MSD caps are junk.

I will be keeping an eye on the Borg Warner cap to see if the same thing happens.

[afret]

Here read this thread:

332-428 Ford FE Engine Forum


The spring arm on the rotor in my Mallory distributor wasn't touching the carbon button on the cap (about a .05 gap) and this is how they looked after less than 100 miles:








Here's a picture of an unused cap:





I think the arcing between the carbon button and rotor wears the carbon out very quickly. In the above pictures you can see the pitting/burning of the contact arm on the rotor and the cratering of the carbon button.

[decooney]

Makes sense. Nice Network 54 thread. Thanks. Bend that tong up!

Hmmmm. Maybe the reason that MSD does not tell anyone in their directions to check/bend the tong up, or to drill holes in the cap to let the ion gas out, is so we al have to buy new caps and replace their distributors every so often. Just like light bulbs; i.e. engineered that way.

[69boss429]

I had the same problem with the MSD in my Boss 429,can someone give me the part number of the aftermarket black cap that replaces an 8431 MSD cap.
Thanks