Distributor cap uneven wear

[xx88man]

I am looking for the cause of an engine vibration. I found uneven wear on the inside of the distributor cap. Most terminals look fine but 7 and 2 (side by side) look like the rotor only makes contact with one side of the terminal. I haven't seen this before but it doesn't look normal to me. Will get a new cap and rotor and put on to see if it helps. For the life of me I can't figure out how to post pics here now. 

[Jay Bee]

If you're interested, here's mine before I cleaned up the contacts - picture is huge if you download it.

[MoparLeo]

Have you checked the main shaft for excess side play ? Checked with  timing light for fluctuations ?

[bdschnei]

"I found uneven wear on the inside of the distributor cap. Most terminals look fine but 7 and 2 (side by side) look like the rotor only makes contact with one side of the terminal."

Yeah, check the distributor shaft play for sure. The rotor tip shouldn't be touching any of the individual cylinder terminals. The spark jumps the gap.

[xx88man]

This is what my terminals look like

[RzeroB]

As you said, 7 and 2 are side by side. Perhaps there is a slight manufacturing deformity resulting in the cap NOT being a perfect circle?? Try substituting a different cap and see how it goes??

[xx88man]

As you said, 7 and 2 are side by side. Perhaps there is a slight manufacturing deformity resulting in the cap NOT being a perfect circle?? Try substituting a different cap and see how it goes??

That's a good idea. I have the cap I'll try it. Thanks

[Kowal]

You did not say what engine, but I had a big block once with an upper radiator hose was getting soft from age and losing shape, it leaned against the cap which caused the cap to move and creating what you have seen.   That is a worst case.  I would swap caps, being careful to get any plastic flash out from the location notch on the cap where it meets the distributor.   Also make sure the springs are engaging the cap as they should. You can get a cap quickly from Rock Auto or Napa.