Carbon button in distributor cap broken off, melted

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SeattleQQ1Fish

SeattleQQ1Fish

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The 273 in my Barracuda started shaking at idle, and so after reading a bunch of threads, I thought the culprit was possibly a misfire. I bought a new set of plugs/wires and after removing the distributor cap, I could clearly see the carbon button was gone and the spot where it was at is melted. The engine is original except for an aluminum intake/carb and the distributor, which was replaced in the last six months by the previous owner. I can't tell what kind it is, but it appears to have an electronic ignition module. Any ideas what would cause this kind of damage? And would installing a "real" Mopar electronic ignition system/distributor prevent it in the future?

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Not sure If the po could have known but I've had brand new caps come with the button broken right off with them floating around in the box and wondered how that could even happen.
 
First thing I'd do is make DARN sure you have the correct cap. Other than that, something like an open plug wire allowing very high voltage, or as said above, "just one of those things" type failure. You might also do a Google on "rotor phasing" means the syncronization between the point in time at which the spark happens (the trigger) and where the rotor is aligned (or not) with a cap contact at that point
 
This is caused by having a gap between the rotor and the cap. Over time it starts arcing and eats away at the cap and rotor. Just replace the cap and rotor and be sure there is no gap between the two.
 
Murray said:
This is caused by having a gap between the rotor and the cap. Over time it starts arcing and eats away at the cap and rotor. Just replace the cap and rotor and be sure there is no gap between the two.
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Exactly.
That type cap needs the rotor with the springy type contact that sticks up and contacts the cap button.
That is a skip white style HEI electronic distributor and as a matter of fact I have one of those here that the same thing happened to.

One thing about those is some were shipped with really shitty rotor phasing.
This one was so far off the engine would miss until the mechanical advance would start coming in and get the rotor closer to the post it needed to fire.
(Which I'm sure didn't help the cap burning problem any)

I had to redrill and move the pickup base plate about 1/8 inch to make it fire where it should.
Short version is it ran like **** at idle and low rpm's.
 
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This must’ve been one that shipped with shitty rotor phasing; it fried with probably less than five hours on it. And it did run like **** at idle and low rpm’s.
 
I noticed that it didn't have the springy contact to, never seen that before.

Jeff
 
Oh and that's a Skip White distributor, straight from the bowels of China.
 
I've had so much good service out of the Chrysler electronic distributors that in my world using anything else is just plain wrong...
 
I thought Skip White was a surfer or snow boarder, don't they have chewing gum named after him too.
 
Oh Wow! Whites Performance and Machine at the old Nickels Speed Shop... I never associated them with Mopar anything, looked like an all Chevrolet kind of place to me!
 
yellow rose said:
Amazing. Never heard of Skip White.
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And NOW a lot of their stuff is pretty good quality. At first, their junk rate was way up. I have one of their distributors on the 351M in my F250. It has the big GM style HEI distributor made onto a 351M shaft. It's a nice piece. Hasn't given me not one problem since I put on over four years ago. One wire for it to run. Two since I have a tachometer. Module goes out, everybody has them. Cheap. Same cap and rotor as the Chevy, same advance weights and springs. What's not to love?
 
If it was me....change cap and rotor for correct matching ones and run it.
That distributor may be just fine.
Good luck avoiding Chinese products.
 
4spdragtop said:
If it was me....change cap and rotor for correct matching ones and run it.
That distributor may be just fine.
Good luck avoiding Chinese products.
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That's what I would do......IF he can find them! They don't make that distributor anymore so that may be difficult. My buddy @clhyer has one on the Duster and it runs good.
 
Wont that distributor "accept" a parts store cap and rotor? Or are they specific to skip? To me looks like mismatched cap and rotor only.
RustyRatRod said:
That's what I would do......IF he can find them! They don't make that distributor anymore so that may be difficult. My buddy @clhyer has one on the Duster and it runs good.
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4spdragtop said:
Wont that distributor "accept" a parts store cap and rotor? Or are they specific to skip? To me looks like mismatched cap and rotor only.
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Certainly "something" matches up, but I don't know "what".
 
Garrett Ellison said:
I've had so much good service out of the Chrysler electronic distributors that in my world using anything else is just plain wrong...
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Chrysler was the 1st to come out with the electronic set up like that . I think they got it way right. I bought one of those Dizzy's for my big block and threw it in the trash! I then put MSD box in and only got a year out of it and you had to crank a while before it fired. My stock set up fires up instantly and runs great. Just my 2 cents.
 
Think it was a mis matched cap and rotor. That type of rotor needs a spring loaded carbon button. Almost looks like it was rubbing on the cap also.
 
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