Rotor Gouging Cap

I have a 92 Caprice with 305 engine and I have a very strange problem. It seems that the rotor tip is lightly hitting the contacts on the distributer cap causing gouging of the contacts. It happens on ALL the
contacts but is worse on some.
Obviously my first thought was play in the distributer shaft because this particular distributer has more than 300,000 miles on it. The first was replaced by the dealer at about 40,000 miles due to a factory bulletin.
However, there is not even the slightest amount of play on the shaft and the rotor and cap are seated properly. I don't think the shaft is bent because that would show up as hitting on one side.
Any ideas?
One last question, I am going to replace the distributer anyway but there does not seem to be that much clearence between the cowel and the top of the distributer. FSM says remove the bolt and pull it out. Anyone do this in a Caprice?
TIA
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Sean wrote:

Are you sure that what you are seeing is the rotor "gouging" the cap contacts? Every cap that I've ever seen with some miles on it, will have indents in the contact area....this is normal wear from the spark. Same thing happens with spark plugs, the metal electrode gets worn.
Time for a new cap and rotor if this is all that is happening.
Ian
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On Sun, 22 Aug 2004 22:00:14 +0000, shiden_Kai wrote:

It's happening with a new cap and rotor and I even went out and got a different brand cap and rotor to make certain. Also if you put your hand on top of the cap while the car is running, you can actually feel it.
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Can you see anything that might be keeping the rotor from being fully seated?
I assume that you have checked to ensure that the locating tab on the cap is in the slot for it?

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On Sun, 22 Aug 2004 22:32:09 +0000, Silver Surfer wrote:

Everything looks pretty good. After 340,000 on the motor I've become quite good at it :)
It's really very strange as I would expect to see some play in the shaft and I do not.
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Just out of curiosity when did you first notice this phenomenon and what brought it to your attention? Can you point to a particular time frame before which there was no problem and after which there was? What if anything was being done to your machine during this time frame?

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On Mon, 23 Aug 2004 01:04:57 +0000, Silver Surfer wrote:

I just replaced the cap and rotor today with the same brand I have always been using. When I started the car I heard whatt sounded like a ticking valve, or an injector making noise. I put my hand on the cap and I could feel a slight knock which corrosponded to the noise. I turned off the engine, removed the cap and rotor and sure enough I could see a very, very light scape mark on the caps electrodes. A little more on one side of the cap than the other.
Thinking I didn't have the rotor/cap seated I tried again with same results. Just for kicks I tried a different brand cap and rotor I had laying around and had the same thing.
If I put my hand on top of the cap and gently flexed it to one side or the other (you can barely feel it move at all), witht he car running I could make the sound change.
I took a look at the old cap and the electrodes had deep grooves in them, yet I don't recall hearing any sound.
Hmmm.... That's odd...
Turns out, I play with the wires on the cap, just twisting them a little while the car is running and the SOUND GOES AWAY!!!
Possible arcing noise due to positioning of the wires?
Even if so, why the mark which to me looks like a slight scrape not the normal mark?
It's all very strange but I think it is fixed.
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This might just be normal wear in the distributor ... I think you said it had 350K on it. Try moving the shaft up & down in the dist housing, there shouldn't be much slop. The contacts in the old cap may have been worn down slowly over time & the interference is only now showing up with the new cap. This 'may' affect your engines' timing. Get a replacement dist at the wreckers with less miles, check the part number in the casting & get the same one.

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Went back and reread your original post. It's hard for me to envision how a distributor shaft could get bent, but would that not cause the problem you are experiencing (or were experiencing)? If the shaft is bent the end of the rotor would have a slight orbit and likely contact all of the high voltage contacts inside the cap. You should also see a circular wear patter on the rotor button as well assuming that it has had enough action to show wear.

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On Tue, 24 Aug 2004 00:26:18 +0000, Silver Surfer wrote:

Yea, that's what had me confused as well. In addition, if the thing was hitting, even on the old cap and rotor, it would have destroyed itself in short order.
I finally found the problem and it was indeed arcing of the wires. I ran the car last night with the hood open and sprayed a mist of water on the cap, the new cap, and I could clearly see arcing between some wires.
I replaced the wires and all is well.
I gues the *marks* on the inside of the new caps electrodes were just normal, although they sure as hell looked like physical contact had been made to me!
Bottom line, wires fixed the problem.
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