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is anyone having a problem with the distributor cap center ball inside where the coil wire goes to. on the inside center there is a ball shaped terminal that rides on top of the rotor, well mine keeps getting flat I replace it and same thing happens. I notice that when I went to the grid... new coil, new plug wire. new battery, new 7730 7720. msd billet distributor with large ford cap
 

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My MSD cap and rotor are doing the same thing, just ordered a new cap and rotor. I have all the recommended parts from MSD, Digital 6, coil, new MSD wires and Pro Billet Distributor. All wiring correct and using their shielded cable to the Distributor! Any Ideas?
 

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Discussion Starter #3
well is going to do it again within a few passes..
o and I forgot the rotor part that rides on the cap gets burned
replaced cap and rotor sevral times
 

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Use to have same problem bend tab up on rotor and mine stopped doing it.
Yes, the tab must remain in contact with the cap and also fairly tight against it. To much vertical movement of the shaft inside the housing is usually the main cause. When the tab and cap lose contact with each other from the constant bouncing around of the shaft they arc between each other and burn the tab. You can also space the tab up some so that it applies more pressure to the cap or make one out of a thicker gauge material because even though bending it helps, it will eventually settle back down to its original tension and location. On some rotors you can place a spring under it, just take the precautions to make sure it stays in place.
 

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This happens because MSD ignorantly copied the dimensions of a GM point distributor with all the end play shimmed out of it. Adding the .090” or so shim pushes the shaft, and with it the rotor blade, down from the cap. Stock GM Chevy distributors have from .060” to .100” end play ….which does not hurt a thing …because the load of driving the oil pump thrusts the gear up against the thrust washers and the bottom of the housing. The original GM design correctly located the rotor blade and cap carbon button when the shaft is pushed up, which it will always be when the engine is running and the oil pump is pumping oil.

The MSD dumbasses copied a modified GM distributor and didn’t notice the modification causes this problem. People think the endplay is bad because it says so in the magazines.

For about 15 years they made the billet distributors shimmed so tight with so little end play that when they got up to operating temperature in a running engine the aluminum housing expanded so much more than (twice as much as) the steel shaft that all the end play was wadded tight and the advance mechanism locks up. Still see this once in a while.
 
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