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

[decooney]

Have any of you guys noticed premature failure of MSD distributor caps, where the carbon electrode little button on the inside/center of the cap errodes away or breakes off?

It seems about every two years or so (every few thousand miles), I'm buying another cap. I do check it every 4-5 months and clean the inside terminals; but this time it was a bit different inside. Today, started the car, it all the suddend started backfiring (popping loudly) every 15 seconds or so. I thought to myself, oh, probably some moisture in the cap since my car has been sitting for a while. So, we stop, pull the cap, and on the inside is this white/grayish ashy looking stuff collected on each terminal on the iside and you can see it inside in small granules in the cap. So, I look at the center betton that is usually a have circle sticking out and its ground off flush. In fact, it was indented a bit. My cap does not have the spring loaded center terminal, it was fixed like a half-round ball protruding slightly outward. My plug wires are good, but I have not changed my spark plugs in a year or so, and maybe I'm building up some resistance in the spark plugs which causes resistance in the cap; not sure till I pull them all out and check again...

I'm thinking I might try a standard Small Block Chevy cap instead or looking at feedback from others who've noticed premature wear on these MSD caps? Do you think it's possibly from another resistance factor somewhere in the cap, wires, or plug. Just trying to figure out why those center electrodes degrade and come apart which appears to be prematurely. That's symptoms.

Any ideas?

Thanks, DC

[bobcowan]

That's happened to me once with a Mallory cap, and to a friend of mine with a Mallory cap. I now carry a spare cap and rotor. And I put in a new one every year.

[xlr8or]

Mine went flat in 700 miles. Just put a new one on yesterday.

[CHANMADD]

I have no idea why you guys all want to use that MSD. Is it so much beter than a normal electronic ignition like an HEI??

[decooney]

Just spoke with a buddy of mine at GTAuto. He said there may be (not sure yet) materials issue with the carbon electrode in them on the MSD caps; he's experienced the same thing on cars with Accel and MSD/Multiple Spark Discharge combined with high intensity/high voltage type Blaster coils. The theory we have now is once the gap begins between the rotor and the electrode, it starts the arch welding scenario and the degradation gets worse quickly. We agreed on an alternative approach to try. I'm going to try a standard heavy duty Borg Warner cap for Small Block Chevy; brass terminals and 3 year warranty at Kragen. Same Gray color as stock Ford; looks good, so I'll give it a try. We'll see...

[thudmaster]

Duane, I have fried a couple of those caps on my small block. On mine I found that the lead wires coming into the cap (2 wires) were worn and arcing inside the cap.

[xlr8or]

Duane can you send me the part numbers you get? Do you just need the cap or rotor change as well?

[decooney]

Originally Posted by xlr8or

Duane can you send me the part numbers you get? Do you just need the cap or rotor change as well?

xlr8or,
I have not mounted it yet, and will in a few days; so don't take my word on the part number yet till I try it; using Borg-Warner C158 has brass terminals and 3yr. warranty. Here is a link to use, if it works. I am using the MSD rotor. Mine is gray, not black though.

Part Link to C158

[Tom Kirkham]

Those of you that are going through distributer caps and rotors way faster than normal need to check the rotor phasing to the cap.

[convincor]

This is why I prefer a stock distributor with a electronic conversion.
If something happens to the cap I can pick one up at any autoparts store.
Hate to be 75 miles from home and stuck on a Saturday afternoon and have to wait til monday to special order a replacement.. just my $.02

[bobcowan]

Originally Posted by Tom Kirkham

Those of you that are going through distributer caps and rotors way faster than normal need to check the rotor phasing to the cap.

?????????

Could you explain that, please?

[Rick Parker]

My observations......

Several years ago when MSD brought out their "Small Diameter Pro Billet" distributors for the 289/302 I just had to have one. I was near the front of the line. Anyway... it originally used a black cap sourced from an Application from an International truck V8, and a Chevrolet style rotor. The cap had aluminum terminals which I wasn't crazy about. With a little research I found that Napa, KEM and a few others made a cap for that application with brass terminals which was interchangable. Fast forward a few years and MSD brings to market a replacment cap made from red ryonite (their red plastic, nicely done). BUT after checking some dimensions with a dial caliper, I realized the tip of the rotor was passing about .160 UNDER the brass terminals in their cap, it did not pass to the inside and next to the terminals as I expected they would. TO me this distance seemed excessive and would seem to create a lot of resistance. It was also appearant that the top blade on the rotor was not touching the button in the center at the top, again creating resistance and arcing. That along with the fact that the cap was a little taller but only available (at the time) in red sent me back to the earlier ones made by NAPA , KEM, etc.
Now (this month) MSD is releasing the original red only cap in black and has also brought out a rotor that has the ability of allowing the tip to be adjusted and improve the phasing of the rotor tip within the cap. So we will see if it works any better.


MSD Adjustable Race Rotor PN8421

MSD Cap Rotor Kits PN84335
Black Small Diameter Cap (cap only) PN 84313 (Top Cap)

These also fit 351 distributors using similar caps.

It's just a part that requires occasional replacement to keep a sharp edge on your ignition system.

[scootter]

Duane,
I burned two up before I realized the rotor tab wasn't making good contact with the cap. I bent it up a bit, and have had this cap on for about 12k or more and still looks fine.
Scott

[DonC]

Duane:
Sorry to hear about your problems. My MSD distributor and cap had just about 20,000 miles on them when I changed it out for the Mallory that came with the EFI set up for my 428 FE. Didn't need changing, just that they system came with the new distributor.
It would appear that MSD can make some long lasting parts but you just have to get your hands on one of them.
DonC

[patrickt]

Originally Posted by bobcowan

?????????

Could you explain that, please?

[diegokid]

I went through this a few years ago having the same problems. I bought a NAPA distributor cap with brass and the matching rotor. I even used a ohm meter to check the resistence between the two caps. The cheaper NAPA had less resistence and cost less.

[mr0077]

Same here, the MSD red cap "wore out" pretty quick, switched to a brand X Chebby cap and it has been running fine for the last 6-7 thousand miles. Maybe the new MSD cap I ordered but never installed is the new improved version...

[decooney]

Fixed.

Part Link to C158



Just installed Borg Warner cap #C158. Took the car out, ran it for a bit, works great. Funny thing is my car was actually idling about 300rpm higher than normal after I installed the new Borg Warner Cap. I can't imagine the terminals moving that much between caps for more achieved advance. Will recheck timing next too. The new one snaps down and locks in place nicely. Bought it at Kragen/PartsAmerica for $18, is grey in color like stock, three year full replacement warranty. Sort of a suprise really... Just a tad more snap/crackle/pop now and the motor winds smoother and faster to the higher RPM range now. It seems my former MSD cap must have been failing and had become degraded for a tad longer than I had suspected. Indexed or not, so far so good.

[thudmaster]

Then I expect to see it saturday at the "Waffle Bash"............

[Cobrabill]

Originally Posted by CHANMADD

I have no idea why you guys all want to use that MSD. Is it so much beter than a normal electronic ignition like an HEI??

YES it is...