MSD Pro-Billet Cap & Rotor Wear????

[Bunkie314]

Anyone had the cap carbon ball wear off and getting a lot of material transfer from the rotor to cap terminals? I'm starting on number 3 cap and rotor replacement with 800 miles now. I'm still tuning and get wet plugs which always leads me back to the damn cap and rotor. I do have another unit to compare it, but initial "feel" checks everything seems to be ok. I am running a bronze gear which I had the machine shop set up due to the wonderful directions on the MSD literature. I haven't pulled the distributor yet, but I'm starting to wonder if something is off tolerance. No felt side clearance, axial play has no feel difference to the extra one, and just a little cam gear clearance.

I have several grounds installed and was very particular on wire routing for EMI and EMF. I don't have any issues with operation, just cap and rotor wear. And yes I replaced both at the same time.

I couldn't post on the MSD site yet since they have to approve you, but I did do a fairly extensive search and didn't find and related threads.

[496fe]

A problem with many FE's is that the distributor hole in the manifold doesn't line up with the block hole. This might be causing the distributor to be bolted in cocked.

Try installing the distributor without the seal and see if it sits in the middle of the hole in the manifold. If it doesn't, you need to move the manifold or the hole to match.

Good luck,

Brian

[Rick Parker]

If you have a set of calipers, carefully measure the depth of the cap from the bottom to the tip of the carbon button. Then measure from the surface the cap rest on to the spring contact that rubs on the button, is it actually making contact or is there a distance that is causing arcing and overheating of the carbon button. It must actually rub on the button. I was surprised to find unusual internal dimensions in MSD's Small diameter Pro Billet Distributor and their "Red" cap. I measured over .160" from the upper surface on the tip of the rotor to the bottom of the outer tower contacts, that seemed excessive.

[Bunkie314]

Rick,

Yes it is touching the carbon button alright, grinds it off it touches so well. It has worn off the carbon button down to the steel support and now started in on that.

[Rick Parker]

Use an OHM meter and check the coil wire and Plug wires. The rotor should be touching but not grinding. Is the coil actually listed as compatable with the MSD box you are using? What plug gaps are you using?

[Bunkie314]

The entire ignition is per MSD outlines, pro billet, 6al, blaster 2, 8.5 mm wires. Wire check ok, looked at that first. plug gap at 50, comp ~ 10.25 to 1, autolite 035 plug.

MSD tech line stated to high of resistance in the system and to increase plug gap. What??? Larger plug gap would have an even higher resistance. I wonder if he ment to high of current and to increase gap to reduce current flow.

[scootter]

I burned up 3 caps till I found out the tab on top of the rotor wasn't high enough. I thought it was wearing out, when it was really burning up.
Scott

[Bunkie314]

Scott,

Did it have a smooth, almost machined or sanded, appearance? What did you do?

[pgermond]

Interesting discussion..... I'll check mine and see if there is an issue.

[Bunkie314]

I've talked with a couple of other guys locally that state they are replacing their caps every season. One guy in particular is saying that he is seeing the same thing, of course these guys are running step controls, nitrous, etc. which I am not. Still though, something is off and I don't particularly care for the idea of $50 every 400 miles for a new cap and rotor.

I did ask this direct question on the MSD troubleshooting site on what the expected life of the cap and rotor is. See if I get an answer.

[scootter]

Bunkie,
When mine burned up it was gone. Nothing left but the holder that keep it in place. All's I did was to bend the rotor tab up a bit so it hits before the cap seats all the way down.
I have had this cap on now for about 7k miles with no problem. I am running the 6AL MSD box on my 514.
Scott

[Anthony]

I've burned up a cap or two. Also, I've had the contacts corrode severely as well. I had drilled a couple holes in the side of the cap per MSD recommendation to correct this. Running MSD pro-billet distributor, MSD Digital-6, MSD wires.

I'll probably never buy MSD again. I'll try Mallory next.

[rokndad]

Adding a little 100 octane to the fire...My MSD coil contact in the cap ground off today as I was timing the engine. It just died and I ground the batteries down trying to restart. Pulled the cap and there it was....ground flat or broken off to the aluminum holder. Ordered a new cap and rotor today, and will make sure tab on rotor is bent up far enough for direct contact. I'll bet it wasn't touching and arc'ed the darn thing up. I also noticed a lot of build up or corrosion on the individual brass contacts for each cylinder. Guess I'll drill holes as well for venting.

[priobe]

Has anyone figured out the fix to this problem. I am experiencing the same problem.

[Jerry Clayton]

A lot of these things happen in cars with poor grounds---I'd suggest running a number 6 wire from the block to the battery ground

Jerry

[priobe]

Jerry,


Good idea.
Thanks for the response. I will add that to my list of thing to do.

Thanks

[priobe]

I have also read in previous threads that people change the MSD cap for a International Harvester V8 from Napa.

Does any one know what year to ask for?

[ST]

Originally Posted by priobe

Has anyone figured out the fix to this problem. I am experiencing the same problem.

This is a quote from the MSD tech forum:
"Assuming that the carbon button was not damaged in transit, the only thing that I can see that would cause the carbon bushing to prematurely wear would be if the rotor tab was not making firm contact with it. If the energy was arcing from the bushing to the tab this will cause the carbon to wear away quickly. Upon installation of a new rotor (in any installation) we do recommend verifying that the tab is making firm contact. One way to do this is to apply a small dab of dielectric grease to the tab, set the cap on as if it was installed, remove the cap and look at the impression in the grease. You should have an indention down to the metal, if not you may need to bend the tab up slightly in order to get the proper tension on the tab.

The post is not a servicable item, there is no replacement part for it."

[PatBuckley]

A chevy cap is interchangeable - I can't recall if it is from a big block or small block, but it is much cheaper. Black, too.

I was also told that if you use the MSD cap with the George Jetson looking tower they last longer.

Good grounds are always important.

[scootter]

Have you made sure your rotor tab is making good contact with the cap. Like I mentioned in my other post, mine was burning up because the rotor wasn't bent up high enough to make good contact with the cap. I have about 13k miles on the same cap now.
Scott