Distributor Cap Question
Thread Starter
Instructor
Joined: Sep 2001
Posts: 201
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From: Holbrook NY
Distributor Cap Question
Hi all. I have a question regarding a standard non-hei distributor cap on a 71 small block. I had an ignition miss at idle and cruising speed. The points were burnt and I replaced both them and the condenser. That got rid of the miss at cruising speed but I still had the miss at idle. I then looked at the distributor cap and the inside contacts were all discolored and pitted. I replaced the cap with a new good echlin one and the miss went away, for about 2 days. It came back today and I popped the new cap and noticed the contacts looked pitted already. Anyone have a thought as to what is going on?
Specs: all stock
Thanks.
Specs: all stock
Thanks.
Le Mans Master
Joined: Aug 2006
Posts: 7,411
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
distributor cap.
Have you checked the dwell? It should remain steady as the RPM's increase.
The end gap on the gear end could be to large, or mabye the side bearings have to much wear.
My cap has been on since 10-06-07 and looks like new to me.
The end gap on the gear end could be to large, or mabye the side bearings have to much wear.
My cap has been on since 10-06-07 and looks like new to me.
Thread Starter
Instructor
Joined: Sep 2001
Posts: 201
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From: Holbrook NY
Yes I did replace the rotor as well with an echlin one. I have another old car with a non-hei distributor and the cap looks great in that one too. So it makes me wonder if there is too much voltage going through the system. The car is all original with 42k miles so I was thinking of replacing the coil and or ballast resistor.
Pro
Joined: Dec 2006
Posts: 694
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From: tx
You'll usually fry the points if there is too much voltage. If the ballast goes bad, there is usually a drop in or no voltage.
You may want to check the points visually to make sure they are not burnt now. Also, the dwell is important - do you have a dwell meter?
I would also visually check the cap and rotor for metal to metal contact. Could you have worn distributor bushings causing contact between the cap and rotor?
You could also check the voltage coming form the coil to make sure it is not too high. Being its a '68, don't trust that the wires are delivering the full voltage either. Check at all points of voltage (at the coil, at the distributor, etc...)
You may want to check the points visually to make sure they are not burnt now. Also, the dwell is important - do you have a dwell meter?
I would also visually check the cap and rotor for metal to metal contact. Could you have worn distributor bushings causing contact between the cap and rotor?
You could also check the voltage coming form the coil to make sure it is not too high. Being its a '68, don't trust that the wires are delivering the full voltage either. Check at all points of voltage (at the coil, at the distributor, etc...)
Thread Starter
Instructor
Joined: Sep 2001
Posts: 201
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From: Holbrook NY
Dwell was set with a dwell meter to .30" and it ran great. Someone had changed the coil and it says "external resistor required", which is attached to the side of the coil. Distributor shaft feels good and tight, I will check the condition of the new points to see if they are burnt. (As soon as the kids go to sleep) 
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Are you sure that's a 'resistor' on the side of the coil and not the ignition noise suppressor capacitor? That's usually where it resides. I believe the '68 still used a ballast resistor mounted to the firewall near the coil. '69-'74 had a resistance wire built into the wiring harness. If you are getting a full 12 vots DC to the + terminal on the coil (engine block is 'ground') when the engine is running, the ballast resistor/resistor wire is no longer in the system. That would definitely cause an over-voltage condition from the coil and burn points up pretty fast.
