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LCompton
10-11-2003, 04:15 PM
I have a 73 corvettte, 350, with an MSD 6A and Pro-Billit distributor (PN8572) that was on the car when I bought it about a year ago. The car ran fine until recently. On a short trip it started to skip under part or full throttle. Thinking the plug wires were breaking down, I replaced them as well as plugs, cap, rotor, and coil. The new parts weren't put on all at one time, rather, new part, test, new part, test, etc. Each time, the same thing. After just a few miles, skip would develop under load. After all parts installed, car ran great for 10 miles or so, then started skipping throughout rpm. As I tried to get the car home, I started losing more and more cylinders, running on only 3 or 4 in the end. Now skip is there from start-up. When I pull a plug wire from the distributor cap, the fire is strong, but seems like only once every 2-4 revs. When given throttle, spark all but disappears. The motor still starts easily, but begins skipping immediately. I ran the tests on the 6A and it checked out OK. I also checked the new plug wires with an ohm meter and got 9 to 25 ohms of resistance, depending on length of the wire. I then checked the wire going to the distributor for the magnetic pickup. I got a reading of 0.605. On higher settings, the reading was an open line. Does this indicate the problem is the magnetic pickup in the distributor? If so, is there something would have made the pickup go bad?

msdtech4
10-13-2003, 11:31 AM
LCompton,

That does seem like a really bad number on the pick up. The normal low reading is 250 ohm's. Put a timing light on number one and rev it up and see if you loose spark or not. (Try this on the coil wire also) If the reading are accurate on the pick up, that would be the first thing I would replace. Since the secondary parts have been changed and the likely hood of them being bad I would start there.

Thanks,

MSD tech4

LCompton
10-20-2003, 09:39 AM
I'm still working on this problem. I ordered a new magnetic pickup and ran into difficulty getting the old one off. The screws that hold the part in the distributor are positioned where I can only get to the nut. I was able to get one nut off, but on the other one, the screw turns with the nut. Because the screw head is under the attaching plate, I cannot get anything under the plate to hold the screw head. Do I need to remove the distributor from the car. Does the distributor have to be disassembled? I don't want to mess up the distributor and need some instruction on removing the old part. Help!

msdtech4
10-20-2003, 12:38 PM
LCompton,

It is best to take it out of the car to do it. Sometimes you can change it in the car but more often then not it is easier just o mark everything and pull it out. Let me know f you have any other problems.

Thanks,

MSD tech4

LCompton
10-21-2003, 08:53 AM
But how do I get the old part off? Is there a special tool to get under the plate where the pickup is attached to keep the screw from turning. Would also need to hold the screw head to tighten the new part.

msdtech4
10-21-2003, 10:04 AM
LCompton,

No unfortunately you will have to partially dissemble the distributor. The plate you are referring to comes off once the shaft and weight plate are taken off. You will need a set of snap ring pliers, a small punch and hammer. You will need to remove the gear slide the shaft out take the weight plate off(snap ring) then the pick up plate will come off. The non-vacuum advance distributors are easier but this is not to bad.

Thanks,

MSD tech4