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Old 08-30-2004, 08:16 PM
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Intermitent Miss

I got the '67 out of storage the other day. I'm getting an engine miss that's hard to pin down. The 383 engine idles fairly smoothly considering the cam.

The problem is while driving. The engine will be smooth and then miss/stumble for a second. It doesn't appear to be related to any particular speed or load. I also got one backfire when I was "checking the tachometer" for accuracy.

I pulled the carb to make sure I didn't have a repeat of a prior problem with the rear (Holley) needle and seat sticking.

It seems to boil down to ignition. It's got a Pertronix unit that has performed flawlessly for 3-4 years. The distributor cap looked good inside. None of the plug wires are close to heat sources and are routed like the factory did.

Any ideas?
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Old 08-30-2004, 09:06 PM
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fractured plug or wire, fo sho!

K
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Old 08-30-2004, 10:01 PM
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Thanks Killer.

I've thought of pulling the plugs, but since it runs good most of the time I don't know what I'll see. I'll change them out.
The plug wires are a different story. As I remember, at least two of the wires are routed through the engine mounts.
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Old 08-30-2004, 10:05 PM
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two years ago I had the same thing. Swore for hours, looking for vacuum leaks, pulling the cap off, installing new parts.

Fractured plug, #1 cyl. If you're just getting it out of storage, you need to put new plugs in her anywho-

K
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Old 08-30-2004, 10:17 PM
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I'm glad I thought of that!
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Old 09-01-2004, 03:09 PM
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Well, it wasn't the plugs.

If it was a steady miss, it would be easier to find.

Now I'm trying to find some good quality BLACK plug wires.

.
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Old 09-01-2004, 09:39 PM
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Get out your ohm's meter and do a resistance check on your wires. Or take a timing light and run the pickup down the length of the wire(s) while running until you find your break/resistance.
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Old 09-01-2004, 10:00 PM
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what causes them to fracture?
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Old 09-02-2004, 01:31 AM
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Intense heat. They can take a lot of radiant heat but direct heat over time will harden and crack the wires.
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Old 09-02-2004, 08:11 AM
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Thanks Sig.

I noticed this problem just slightly the last time I had it out on the freeway about a month ago. But, it didn't occur at street speeds.

I'm going to look for wires today. I've also resurrected another one of my old points distributors to sub in for the Pertronix that's in there now...working up the line from the plugs.
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Old 09-02-2004, 01:24 PM
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If it has been sitting, is there a possibility of a little bit of moisture from the fuel tank working it's way through? I had a Camaro that would run like that every spring for about a tank and a half of fuel and then be fine the rest of the summer. Just a thought.
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Old 09-02-2004, 08:23 PM
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Drop some HEAT in if your having that problem.
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Old 09-02-2004, 09:49 PM
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Good thoughts. I think I've got some in the garage.

I bought the wires today, but got overcome by a raid on my favorite "automotive recycling facility" hunting parts for my '72. Where has the Summer gone?

The saga continues.
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Old 09-08-2004, 11:08 AM
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Update

Well, after trying everything, I took it out yesterday. It ran fine for about ten miles and then began to miss again. It backfired and then ran smooth for a couple miles. Then backfires again.

I decided to nurse it home. I got about two miles from home and I was getting a "plethora" (as in a whole bunch) of backfires. It would quit but restart.

After coasting into the garage, I pulled the distributor. From what I can tell, the Pertronix upper ring was warping under heat and rubbing against the stationary unit. There's supposed to be an air gap. That was probably sending all kinds of strange electrical impulses.

Just got done installing a points type distributor. I haven't set points in years! Dwell, we don't need no stinking dwell.

Seems to run fine now.
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