Wire zapping manifold shield

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72Plymouth

72Plymouth

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I was hearing this noise but didn't sound like it was near the distributor and the engine would have faint hiccups. Found that the spark was jumping the wire to the manifold shield causing a miss every now and then. Looks like it has been happening for a while because the metal was eaten away where the spark was hitting.

What have you guys done to prevent this? I'm sure it could use a new set of wires. Before I jump on MSDs, are there any other brands that you guys prefer that are better insulated OR should I simply get some kind of insulating sleeves near the base of the wires? I believe those are more for heat though.

Thanks
 

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When sparks jump from a wire or other component,

IT IS BECAUSE there is something wrong

You could have a problem in that cylinder, IE burned valve, other lean condition

a broken/ damaged spark plug---they can lose continuity inside the ceramic

A bad (open) wire

All of the mentioned conditions --essentially an "open" removes the loading effect of the firing cylinder which allows the voltage to RISE and just like lightning, the spark voltage is now looking for the easiest path to ground.

It may be that the manifold/ shield being in poor shape overheated the wire and is the direct cause of the damage. If it rattles around and contacts the wire "in flight" might just be

If you want a real education, go out after dark, raise the hood, and run the engine. You'll soon see where the spark/ corona is "trying to go" to ground

If you have big enough nuts, running your fingers along the wires will soon give you an education, too. Not recommended with high energy, multiple discharge gear
 
Looks like you have bad wires causing that. As stated spark will follow the path of less resistance to ground. I run the Accel yellow wires on mine that you install the ends yourself. Fairly cheap and never gave me troubles.
 
chryslerfat said:
Looks like you have bad wires causing that. As stated spark will follow the path of less resistance to ground. I run the Accel yellow wires on mine that you install the ends yourself. Fairly cheap and never gave me troubles.
Click to expand...
I personally find these to be junk IMHO. Go with the similar kit Taylor makes. they have alot of boots and everything. what happened is probably you burnt a hole in your wire and are gonna need some 90* boots on those wires to keep the far away from your manifolds. No offense to your Chryslerfat, just saying, I like the Taylors better as they are a better made product.
 
67Dart273 said:
When sparks jump from a wire or other component,

IT IS BECAUSE there is something wrong

You could have a problem in that cylinder, IE burned valve, other lean condition

a broken/ damaged spark plug---they can lose continuity inside the ceramic

A bad (open) wire

All of the mentioned conditions --essentially an "open" removes the loading effect of the firing cylinder which allows the voltage to RISE and just like lightning, the spark voltage is now looking for the easiest path to ground.

It may be that the manifold/ shield being in poor shape overheated the wire and is the direct cause of the damage. If it rattles around and contacts the wire "in flight" might just be

If you want a real education, go out after dark, raise the hood, and run the engine. You'll soon see where the spark/ corona is "trying to go" to ground

If you have big enough nuts, running your fingers along the wires will soon give you an education, too. Not recommended with high energy, multiple discharge gear
Click to expand...

Thanks for the info. The plugs have been changed recently, and from the looks, it has been zapping the metal over the years. So the plug wire is probably worn. I can pull the plug to check it out too.
 
chryslerfat said:
Looks like you have bad wires causing that. As stated spark will follow the path of less resistance to ground. I run the Accel yellow wires on mine that you install the ends yourself. Fairly cheap and never gave me troubles.
Click to expand...

The wire was only jumping the spark to the manifold shield only when it was close to it (about 1/4" or so). But still, the wire should insulate that to prevent it. Just weird that the spark would rather jump the wire than go to the plug it's directly connected to. So just hoping if I got new wires it doesn't do that.
 
72Plymouth said:
The wire was only jumping the spark to the manifold shield only when it was close to it (about 1/4" or so). But still, the wire should insulate that to prevent it. Just weird that the spark would rather jump the wire than go to the plug it's directly connected to. So just hoping if I got new wires it doesn't do that.
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Try and get some of the spark plug sock things if you do so. they may help. They are like an insulation tube sock dealy that slips over the wire. I can't think of the name at the moment, but they are pretty cheap, but be sure to replace those wires as misfires are bad for your engine and sap HP and TQ and fuel efficiency bad.
 
Update
Took a few wires off to test with the meter and they were all in the same ballpark, but did find that the insulation on one was worn. So looks like it's time for new wires. Also some oil was leaking from the valve cover to the plug and wire so that's gotta be messing with it too.
 

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If you really want to check your plug wires,use a 12V test ltight. ground the test light lead, start the motor and slide the test light along each wire . You wont get shocked as long as YOU don't touch the wires. You may be surprised at how much leakage some wires have.
 
Thanks, I have one of those so will try it that way around the wires, then compare to new ones.
 
DarTT said:
Try and get some of the spark plug sock things if you do so. they may help. They are like an insulation tube sock dealy that slips over the wire. I can't think of the name at the moment, but they are pretty cheap, but be sure to replace those wires as misfires are bad for your engine and sap HP and TQ and fuel efficiency bad.
Click to expand...

They are not cheap.
 
72Plymouth said:
I was hearing this noise but didn't sound like it was near the distributor and the engine would have faint hiccups. Found that the spark was jumping the wire to the manifold shield causing a miss every now and then. Looks like it has been happening for a while because the metal was eaten away where the spark was hitting.

What have you guys done to prevent this? I'm sure it could use a new set of wires. Before I jump on MSDs, are there any other brands that you guys prefer that are better insulated OR should I simply get some kind of insulating sleeves near the base of the wires? I believe those are more for heat though.

Thanks
Click to expand...

I think the metal was eaten away by rust, not electrical discharge. It's possible that the ragged edges damaged the wires, causing the discharge. The answer will not be better insulation, rather you need to address any sharp edges near the wires. Make sure you use the appropriate looms and clips when you replace your wires.
 
When I was in high school, Dad and I resurrected a Studebaker that sat for about 15 years. It was running, but bad.
That night, I looked under the hood with the motor running and I was mesmerized!
The plug wires were so bad that sparks were jumping all over the place.

Some things you just know you'll never forget! :)
 
The 69-71 Kawasaki 500s had the same problem..brand new.
They had a CDI system on them that put out huge amounts of juice.
And the plugs wires could not handle it.
Running at night, you could see the cobalt blue/white electrical impulses flowing down the wires. Sorta mesmirizing...just don't touch it.
 
Gryzynx said:
I think the metal was eaten away by rust, not electrical discharge. It's possible that the ragged edges damaged the wires, causing the discharge. The answer will not be better insulation, rather you need to address any sharp edges near the wires. Make sure you use the appropriate looms and clips when you replace your wires.
Click to expand...

Good point, could be that too so not ruling that out. Just thinking it was the spark because the other side is fine tho and I think has some white/gray areas where spark has hit too. I'll try to get rid of those sharp edges.
 
Just got the new set of wires! I ended up getting some good ol Mopar ones from the dealer. I was close to getting either Taylor or Moroso wires from Summit but after shipping, the price added up.

The dealer had these Mopar wires for $43 and got them in the next day. They seem well made but will just have to see how they hold up.
 

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Thanks! Hope the new wires blend in ok lol, my motor looks like it hasn't been touched in almost 40 years. At least they're blue.
 
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