#3 Plug Arcing
 

While I was adjusting the idle on the carburetor with the engine running, I noticed that the #3ncopper lead and the #3 plug was arcing to the distributor and to the spark advance rod (which is close to the #3 lead).
It also sounds like the #3 cylinder is missing somewhat.

The arcing did not occur on every revolution but at least every 10 revs or so it seemed. I haven't delved into the distributor and plugs yet until the engine cools down. Any ideas as to what is the problem here?

Re: #3 Plug Arcing
 

sounds like you might have a bad plug and the spark is looking for a ground.

on a model A unlike other cars the distributor cap is the cap that the clips snap on to and the coil wire goes into. the distributor body is the piece with the 4 contacts inside. i have seen those go bad with carbon tracking

Re: #3 Plug Arcing
 

Thanks for the responses. I think I solved the problem. The rotor to distributor housing was all over the place and actually kissing the #3 electrode. I bent the rotor electrode to increase the clearance on #3 to .035" and filed the rest down to .035". Set the points to .022" and retimed. Swapped the plugs around and re-gapped to .035"
Runs good and no random sparks now. I love this forum

Re: #3 Plug Arcing
 

make sure your distributor shaft bushing is tight.. a bad bushing can cause erratic point and rotor gap...