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Discussion Starter · #1 · (Edited)
Looking for opinions really as to reasons for extreme wear to the centre carbon electrode to the distributor cap of thePro Billet MSD distributor on my big block Vette. Even though its been in the car 4 or 5 years its only done about 1500 miles maximum. You can see where its worn right down to the metal retainer. The only reason I could think off was that spring tension on rotor arm 'wiper' was too much - it does seem to show a uneven wear pattern - anyone else experienced this ?


 

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Discussion Starter · #6 ·
Looks like arcing. Or a spanner in the valley?
Arcing yes - but I would have also expected all 8 plug lead contacts to be corroded too - they are fine. Have a feeling though that someone is going to say I should have a ballast?
Frank - notice now I am ignoring the spanner comment! - have I told you about the mouse nest in no.1 cylinder yet?
 

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Do you use a ign box 6al-7 ......... I was led to believe that no ballast resistor is needed with this type of ign coz it needs the full 12v, have you run a new 12v source from key to box as some factory wires have the resistor wire built in running to the coil. Just a thought ................. :tup:
..Nige..
 

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Discussion Starter · #9 ·
Do you use a ign box 6al-7 ......... I was led to believe that no ballast resistor is needed with this type of ign coz it needs the full 12v, have you run a new 12v source from key to box as some factory wires have the resistor wire built in running to the coil. Just a thought ................. :tup:
..Nige..
Yes Nige its got a 6T box - 12v comes from a fresh supply - like you I thought ballast wasn't required!
 

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This along with the ionisation seems to be a fault common to MSD. The smaller the cap then the bigger the problem. The ionisation causes the heavy rusting and corrosion seen internally and probably contributes to electrode wear. MSD also advise making sure you have a really good separate earth line to the distributor. Once that electrode starts arcing then the problem accelerates so as said a good initial contact is essential.
 

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I have the very same setup and yes the carbon button does erode away, it is a well known problem, the worst thing is they dont sell the button on its own so you have to buy a new cap! I must check mine actually.
If you do a google search there is lots of talk about this on american forums.
 

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Discussion Starter · #12 ·
I have the very same setup and yes the carbon button does erode away, it is a well known problem, the worst thing is they dont sell the button on its own so you have to buy a new cap! I must check mine actually.
If you do a google search there is lots of talk about this on american forums.
Thanks buick350 - its good to know its not just my problem alone - I'll check out some of the USA forums. I guess part of the issue is using 'old school' and traditional methods of transferring HT power through a distributor. Wonder if crank trigger set-up has same problems?
 
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