HEI distributor Cap... is something wrong?

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MrSony

Geezer
Nov 15, 2014
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Des Moines, Iowa
I was messing with my distributor today, and I was trying to diagnose a weird miss I guess, my motor seemed to have. All the plug wires tested fine, all the plugs looked almost new (only have a couple hundred miles on them, so they should look good), all the piston tops are lightly blackened by carbon. I took the cap, and coil off and this is what I found. First pic is of the cap that came on the distributor from TA Performance. Never touched it. Took it off once to see inside. Put it on the motor, worked fine ever since. Other picture is of a spare never used cap I had lying around. The TA cap looks all worn down in that area, and it had a bunch of ground up plastic on the little silver nub and the contact on the rotor was blackish. I cleaned the rotor and I put the new cap on. Runs fine, if a bit better than it did. Belt squeals so bad I couldn't really check to see if the motor ran too different. Didn't want to toast my alt or battery. What do you all think happened? Is this normal wear or is something not right?
tacap.jpg
newcap.jpg
 

Bar50

Royal Smart Person
Jan 1, 2009
1,180
870
113
Tulsa, OK
The center contact should be black its carbon, it should stick out some. The other cap looks to be missing the carbon insert that goes in under the coil with a rubber washer and a little spring on top.
 

axisg

Comic Book Super Hero
Jul 17, 2007
2,685
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YYZ
The carbon button is a wear item and it doesn't look too bad. What does the rotor look like ? I'd just clean up the contact points and look out for any reddish or rust coloured dust, misfires, ect.. once you slap it back together

I have seen a few times where they pull too many amps thru the carbon button and it starts to melt the plastic housing on the cap or a defective carbon button create a mess inside the cap. But that's on high mileage poorly maintained beaters from years ago.
Usually a module change ( always keep a spare ), cleaning the ground straps, replacing the carbon button & rotor would clear it up.
So really yours looks fine. The rust coloured dust usually indicates a mis-fire. Whether it be a bad / cracked cap , moisture, ect...
 

Texas82GP

Just-a-worm
Apr 3, 2015
7,981
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Spring, Texas
Is the fuzzy stuff around the carbon button in the first picture plastic shavings? I wouldn't think that is normal. I've never seen that before.
 

MrSony

Geezer
Nov 15, 2014
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Des Moines, Iowa
The center contact should be black its carbon, it should stick out some. The other cap looks to be missing the carbon insert that goes in under the coil with a rubber washer and a little spring on top.
that new cap was just the cap. i swapped the carbon button into the new one.
 
Oct 14, 2008
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MrSony

Geezer
Nov 15, 2014
6,793
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Des Moines, Iowa
I personally used the low ohm button, MSD has them, they look like brass.
https://m.summitracing.com/parts/msd-8412#
Any tips on how to get the spring through the grommet hole without dicking it up? It's a very delicate spring and I don't want to chance it. Mine is fine and all, and I think runs better than the one that was in there, but for future reference it will help.
 

pontiacgp

blank
Mar 31, 2006
29,270
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Kitchener, Ontario
Any tips on how to get the spring through the grommet hole without dicking it up? It's a very delicate spring and I don't want to chance it. Mine is fine and all, and I think runs better than the one that was in there, but for future reference it will help.

I put the spring in dry ice for 30 minutes to shrink it and then grease the hole in the rubber grommet. That makes it's easy to get the spring through the hole..:)
 
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Oct 14, 2008
8,806
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Melville,Saskatchewan
Dielectric grease and patience is good. I have never wrecked a spring yet over the years.
 

airboatgreg

Comic Book Super Hero
Oct 2, 2016
2,863
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Remove the coil and button will go right in. I would look at your plug wires as I suspect you have a bad one. Undo each wire and take a flashlight and look at terminal. It will be nice, clean and shiny on each end. If it is black or corroded you have a bad wire
 
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