MSD Distributor Issues
 

While taking apart a 65 427 Side Oiler I pulled off the MSD distributor cap and noticed it was loaded with some sort of a carbon dust.I took it off and cleaned it out the best I could, replaced the rotor and cap. I put on a GM cap with brass contacts thinking this might help. My question where did all this carbon come from? Its a fair weather car driven only in the summer on sunny days. It's a MSD # 8594 with a 6al box. The car runs strong with no issues but something isn't right here. any input would help.
Thanks

May be the carbon button in the top of the cap where the rotor rides. Make sure the brass tab on the top of the rotor touches the button. Make sure the carbon button hasn't eroded too much. If either of these don't look right, replace the cap, bend the rotor tab to lightly touch.

These marks or carbon build up near the distributor posts often indicate a faulty arc from the points (unlikely points as you have an MSD dissy) or rotor to the plug wire post contacts. There is quite a lot of voltage jumping off the rotor into the posts of the distributor. In some cases where there is just a light carbon deposit, a fine sandpaper or crocus cloth can be used to clean off the carbon. Be aware, though, that too much filing will create too large of a gap on the posts and rotor and result in exaserbated further arcing problems. So in general it would appear that some arcing is going on to cause carbon inside the cap. It may be time for a new MSD cap and rotor, in my world, when you change the cap you also change the rotor at the same time. Also you may want to change/inspect your plugs and spark plug wires and connections. But I would start with the cap and the rotor. Also check the fitment of the cap, make sure that when it is attached (clamps or screws) that the cap is stable, and firm and does not rock or move in any way. In addition, you could take the cap off and try to wiggle the rotor. There should be NO play in the rotor. If there is any wiggle then the distributor will wiggle under RPM and not sweep the rotor in a consistent manner. That could cause arcing. For replacements, I would stay with the MSD brand. Just my two cents.

MSD has a tool card that comes with the rotors that has notches cut out for each type of cap they sell. I had been throwing them away and simply guessed at how far up to bend that tab. I found bending it up too much causes premature wear on the carbon button. So, when you get a new rotor, save that bright yellow/green card, it's handy. I can get the measurements off mine if you need it.

To answer your original question, I have found it normal to see carbon dust in the cap. Word to the wise, keep it cleaned out as this dust coupled with moisture(from condensation or rain) makes a pretty good carbon "glue". This will gum up everything from the cap down to the bushing where it mates to the block. Good luck!

With any distributor cap, whether it has a spring load brush and a fixed rotor contact strip, or a fixed carbon brush and a spring steel rotor strip, you should be be able to "feel" the spring tension as you put the cap on.

I like to see the cap sit up a fraction on it's own weight on one side, then I know the contact is made, before clipping it on.

A lot of caps don't do this.

MSD suffers a lot of "dust" from dry centrifugal advance weights, poor rotor phasing, arc welding with dissimilar metals, and overheating the carbon brush since there is a low resistance brush available.

Gary

I'd love to get those measurements from the rotor card. I can't find them on line.

I would also like to know that measurement.
I could be mistaken, but If I remember correctly, I think I drilled holes in the cap for ventilation per MSD tech staff. That was supposed to help with the carbon issue. They also had me drill #30 holes in the bottom of the MSD box for condensation because it is mounted upside down.

Sorry it took so long to reply, completely forgot. See pics below. If you need full size versions, let me know.

Basically, the slots in the card sit on top of the tab on your distributor. Each slot is for specific models, listed on the card. Not sure if this is downloadable from the MSD website or not.
https://i.imgur.com/EvgIL4P.jpg
https://i.imgur.com/bkeMPMX.jpg

THANKS!

I could not find this on MSD's site, which seems odd. It also seems odd to me how this is not even mentioned in the instructions, but rather it's just the card tossed into the package as an after thought.

I would like to get this card for my tool collection

I don't have any of the cards, but, you should be able to print out the photo's above. I sent a message to Technical Support to see if this is something that can be provided.

I thought I had seen everything from MSD. But I've never seen that.%/

please report back. I'd like one too. I just installed a new rotor and would like to verify the measurement.

I always gave it tho 'ol, "that feels about right". Been lucky I guess.

My car eats MSD distributor caps so every time I order something from
Jegs or Summit I add a cap and rotor to round up to free shipping. My
last was 19 May 19 and the rotor came packaged with the yellow card and
a warning to use it.

That's exactly what I've always done. But, next time I'll put a depth gauge on it and see if lands around 5/16" which is in between the min and max for a #8467 rotor. But if it's way off, then I'll disregard the instructions and continue to use the "that feels about right" method that has worked flawlessly for the last 15 years on the ol' girl.:cool:

Am i reading this right? .27 for #8423 cap? I guess i'll just measure it. But hey, it runs fine. I wonder how much of a difference a few thousands makes? And what that difference would be?

I use Patrick's "feels right Method" realizing that if the tab is too low you
get arcing which kills the center electrode in the cap fairly quickly. If you
bend the tab up too much you put undo pressure on the electrode which is
also not good. I just bend it up enough to "feel a bit of a spring" when I put
the cap back on. Works for me. Next time I'll use the yellow card gauge
and see if that extends the cap life any.

I had the msd pickup corrosion problem also, I bought a new one and sprayed a couple coats of high temp clear coat , seems to be running good, I also used a AcDelco cap 19106458 and rotor from 68-74 CSB. Can you think of any problems with the clear coat? Also drilled the cap

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No more bundle of wires to route.
Reads manifold vacuum.
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