This is a problem I have been chasing down for a while. Ever since I made a pass at the Winterport Dragway in Maine. #7 cylinder spark plug is wet with fuel, but compression is good (160 psi). The distributor has Pertronix Ignition. When I pulled the cap and rotor, the cap appears burned at all contacts. When I removed the rotor, I get a very slight side to side movement of the distributor shaft (maybe .005") but no movement when the rotor is sitting inside the Pertronix collar. The cap and rotor are 10 years old, but they don't have that many miles on them. So, do I try a new cap and rotor first before replacing the distributor?Thanks, Rono

  Ron Lane,  Meridian, ID

Have you checked to see if you are getting spark to #7 cylinder or maybe the plug is bad 

If you've got a consistent timing reading with a light up till the curve tops out, I'd say the dizzy is ok. I've had a number of problems with caps and rotors showing signs like that. I've written it off to hot (mostly MSD) ignitions and coils, and cheap offshore caps.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

What kind of shape are the plug wires?

IMHO Looking at the cap contacts, it appears that none of them have or show any arcing on the flat verticle area where you would expect it. It's on the horizonal contact area where the contact is meeting it at the Bakelite. There also appears to be burn/arcing on the top of the rotor contact. This shows me the rotor contact area is not in the center cap contact area which in my opinion is too high up into the cap. As I understand it, the rotor never touches the cap contacts but should pass by it at its verticle center. This can be adjusted by, in this case, bending the rotor contact down and filing it flat again (parrellel) to the to the verticle plane of the Distributor.

If you guys think I'm crazy tell me but I also have 1/8" holes drilled in my racing caps in the same plane as the rotor between each contact. I was a very high voltage electrician in my working life and know damage exposed corona arcing can do.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

  Ron Lane,  Meridian, ID

Dry lakes has a good eye, I missed that. I'm going to throw this out as an example of both corona and the cheaper caps.

I failed to fully seat the coil wire in the center of the cap. The car ran fine, but one night I had the hood up in the dark and could see a blue flicker at the center of the cap. I turned the lights on, shut it down, and pulled the coil wire. The Bakelite on the center was cut half way around, like with a small plasma cutter. The arcing inside that cap, and the created corona was eroding the Bakelite. Wouldn't have been long till it failed.

Drylakes, I never got over 15kv in our inside work, but even there it was dangerous.



miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Dry Lakes;

I don't think your crazy and I understand what you are saying, except maybe for modifying the rotor contact by bending it down and filing it flat. I will try the new rotor and cap, but if the rotor is not centered in the cap, I don't know what I can do about that. Manufacturing flaw and poor quality control I guess. I did think it was odd that the cap contacts were not burned on the vertical surface, but where the contacts met the plastic.


Rono

  Ron Lane,  Meridian, ID

That you have play without the rotor and none with the rotor must mean something.  I don't see how simply putting the rotor in place would remove play.
Given Drylakes' observation of the rotor positioning relative to the cap, that also suggests something going on either directly or indirectly related to the rotor.
My thought is to make sure that the Pertronix magnet wheel is installed onto the points cam completely and correctly and to ensure that it is not contacting something that it should not.
Examine the magnet wheel for any manufacturing defects.


Lawrenceville, GA

Rono,

    I have seen this problem before on a 59 y-block distributor.That 5/8 inch dia. sleeve that the rotor mounts on,ford calls it the cam assembly has a small horse shoe wire clip that holds the cam assembly from slipping off of the shaft.If that wire clip is bent out of shape when it is removed and then reinstalled without repairing it,it can allow the rotor to ride up and contact the distributor terminals.That horse shoe wire clip acts as a snap ring and fits into a grove in the distributor shaft.A worst problem would be the distributor main shaft has excessive end play and allows the rotor to run higher than it should.If you have a combination square that has a 1 inch wide x 12 inch scale lay it on edge on top of the distributor bowl [no cap] and check to see if the cam assembly can be pulled up more than 1 1/8 inches higher than the top of the bowl.Ideally it only needs to be 1 1/16 inch higher.Good luck.
                
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