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Melting Distributor Cap

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Old Aug 22, 2003 | 03:29 PM
  #1  
johnsjj2's Avatar
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From: Monticello, IN USA
Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
Melting Distributor Cap

After installing my new Holley Annihilator ignition system, with the matching street coil, I have burned up 2 dist. caps already. The hole where the little bushing is on an HEI cap melts, and the bushing gets off center and the car runs like crap. I have taken the bushing out both times, and of coarse broke it in the process. Does anyone know whats up with this? Why the cap keep melting like this. I have looked and nothing has been arcing at all. There are no marks to show anything bad is happening except the cap melts. Is it a possibility the bushing is spinning and making all that heat? I need help, these caps are getting expensive.
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Old Aug 23, 2003 | 09:23 AM
  #2  
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I'd be calling Holley to ask them what's up. Good luck with getting a quick, intelligent response.
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Old Aug 23, 2003 | 06:24 PM
  #3  
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From: Philly, PA
2 Completely different trains of through here (I've been there before, but in my case I kept popping coil wires on a divorced-cap HEI with a similar ignition setup)

1. Install troubles. I don't at all mean to insult you but here's the proper order of install for the cap components in an in-cap coil HEI from bottom to top: cap, rotor button (with spring pointing up towards the coil), big rubber donut (the rotor button's spring sticks through the small hole in the middle), then the coil mashes down on top of it all. In short, it looks kinda funky with everyting laying in there kinda loosey-goosey until you get used to how HEIs go together and know that it all gets mashed down nice and tight and flat when you finally secure the coil with the 4 coil retention screws. End result: the little rotor button stays STATIONARY with the cap with the donut between it and the coil. The rotor's center "tab" presses slightly on and rotates around the tip of the button when the engine is running.

2. Downstream ignition troubles. Big plug gaps or worn out ignition wires put a lot of strain on upstream ignition components. The more strain, the more heat. The rotor button in the cap is a very significant restriction- measuring several thousand ohms by itself (measure it with an ohmmeter if you don't beleive me). If the coil is forced to pass a lot of joice due to worn out plugs/wires/whatever this is where heat is going to build up first. Coil is a close second to "melt down" under harsh conditions.

This is not the total answer probably, but I hope it helps in some way regardless.
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Old Aug 23, 2003 | 07:57 PM
  #4  
305sbc's Avatar
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
You need a low impedence bushing.
MSD sells them.
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Old Aug 23, 2003 | 09:22 PM
  #5  
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From: MN
Car: 2009 Pontiac G8 GXP
Engine: LS3
Transmission: 6L80E
Axle/Gears: 3.27
I agree with 305sbc...they are melting because of the high resistance button...thus creating heat and melting the works...

A low resistance (impedance) button is a must have...

Good luck,
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Old Aug 24, 2003 | 07:59 AM
  #6  
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From: E.B.F. TN
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Let us for a moment take a step back and ask a few questions:

1. Where are you grounding the unit
2. Where are you pulling power from
3. What type of plugs are you running
4. Does the interior of the cap show heat damage (other than the button area)
5. How long does it take to burn out
6. What type of cap and rotor are you using
7. What, if any, damage shows on the rotor
8. Have you inspected your wires and tested for resistance

This should give us a bit more to go on. These unit do a lot and tracking down the gremlin should be much easier with this info. It may be as simple as swapping the bushing... or it may not.
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Old Aug 25, 2003 | 02:24 PM
  #7  
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From: Monticello, IN USA
Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
Thanks for the responses. I called Holley today and they too said there was to much resistance in the system somewhere. The plugs are AC Delco R45LTS I think. The letters may be off. The wires are MSD Spirocore that I just put on about 3 days ago. The first cap was one I got from Jegs, with a matching rotor. Don't recall the exact brand. The second cap is a $8 one from Advance Auto. I know its cheap but I didn't want to keep melting good caps. Main power is from the starter solinoid on the firewall, main ground is to the back of the head. This is also where the ground stap is to the firewall, and the coil mount. Switched 12v is to the factory dist. power source. The 2 mag. pick up wires are shielded and kept away from power, and spark plug wires with a clamp on the firewall that is insulated. All the other wires for the RPM switches and rev limiters are not used right now, so I have them rolled up, and tucked away. I ran those functions values to 0 with the programer. I even used JB weld on the latest cap as a fix to fix the problem, and then get a new cap. The JB weld is melting as well. I noticed Saturday as I took the car to get gas, it was missing real bad. It wasn't a little miss, at a 1000 idle, the car would die, the tach went to zero, then come right back. It was so bad, I couldn't make it 2 blocks to get gas. This sounded like a power wire was grounding out, or the mag pick up wires were sending a bad signal. I took the dist, out today and cleaned everything. Still did it. I started to think with the cap melting, plastic was causing a bad connection between the rotor and the button. Cleaned all that off, sprayed everything with carb cleaner. Took all the paint off the dist. colar and the hold down clamp per Holley, and tried again. Still missing. Only now it would miss at idle and die, not coming back like it was. SO, in frustration I disconnected the whole system from the dist., and put all the old stuff back. This was the Proform HEI kit. It ran real well after I did this. I did still hear a miss, but the tach didn't jump like it use to. I think this is due to fouled plugs. They are real black. I took the car, got gas and ran it out in the country. I forgot I didn't have a main over rev anymore and pegged 7000 rpm with it in 1st. So it is running pretty good, but I want this Annihilator ignition back on and working. What ideas do you have as a possibility? I have thought those wires for the extra rev limiters and switches could be touching something. The car ran the worse while it was moving. When the wires had a good chance of moving and touching something. The ends are not wrapped, just cut straight off. New plugs would help I know. The gap on these is set at .045. And I am using an external coil. Any ideas, or thoughts of what to try.
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