Spark plug wires

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Heehaw
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Spark plug wires

Post by Heehaw » Thu Oct 14, 2021 5:56 am

Working on 24 volts system. Rubber on wire cracked and missing in a few spots. Anyone ever coat them with flexseal.


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Re: Spark plug wires

Post by JMZ421 » Thu Oct 14, 2021 11:30 am

Never did and never will. I would buy new or just use that cloth tape to get by. Are you doing some fording?? John

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Re: Spark plug wires

Post by Heehaw » Fri Oct 15, 2021 3:50 am

Just look ugly

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Re: Spark plug wires

Post by Ken Perkins » Fri Oct 15, 2021 7:59 am

I've seen many neatly wrapped with electrical tape...may have read that in a manual
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Re: Spark plug wires

Post by W. Winget » Fri Oct 15, 2021 9:14 am

Find some black vacuum hose of a correct I.D. carefully slit it in a spiral manor, then wrap it around the plug wire.
If it looks like it will work, then remove the wire, lay it flat, apply glue and repeat the wrapping with some temporary tape to hold it in place until it dries.
Just a thought.
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dpcd67
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Re: Spark plug wires

Post by dpcd67 » Fri Oct 15, 2021 4:13 pm

I still want to make a boat out of Flex Seal and wire mesh like Phil Swift does.
Anyway, I have done what you are asking. Cracked insulation, with some missing.
I used shrink tubing, made for electrical applications. Make sure you get it big enough to slip over your existing wire ends, and then you heat it up with a heat gun and it shrinks to a tight fit, leaving the wire to look brand new.
If you do decide to wrap them, do not use cloth or electrical tape; both deteriorate fast. Use Silicone tape. It will look better and last forever. Or longer than you will anyway. I make wiring harnesses out of it.
Last edited by dpcd67 on Fri Oct 15, 2021 4:16 pm, edited 1 time in total.
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Ron D
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Re: Spark plug wires

Post by Ron D » Fri Oct 15, 2021 4:15 pm

If the inside is following the condition of the outside then anything you do might only be a band-aid, but I understand --- given the cost and rare nature of military waterproof spark plug wires.

I agree with the electrical tape, and perhaps heat-shrink over it. Probably requires some disassembly of one connector end to do it properly (good opportunity to inspect). These cables carry something like 20,000 volts to the plugs.

I think I'd be a little leary of "flex-seal"....while it apparently does a great job as a boat made from a screen door, what about the electrical insulation properties? :lol:
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Re: Spark plug wires

Post by dpcd67 » Fri Oct 15, 2021 4:23 pm

Fortunately 24 volt wiring holds up very well, inside. As long as the ends are still good. Flex seal is liquid rubber and is supposed to make a good insulator, but I have not used it for that. Just a leaking drain pipe for the sink. No electricity involved.
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Re: Spark plug wires

Post by mdainsd » Wed Oct 20, 2021 4:35 am

The outer rubber coating isnt there for insulation as much as at it is for chafing protection for the wire braided shield under it. The electrical insulation is inside of that and is usually some form of red silicone compound.
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Re: Spark plug wires

Post by Chuck W. » Sun Oct 24, 2021 6:04 pm

Years ago, I had an M38A1 that had a set of ratty looking wires. I pealed the hard rubber off, exposing the braded wires underneath. It ran fine, only problem is, when I sold it, the guy who bought it said, "That's a diesel engine!" I said, "No, it's gas, those are just the spark plug wires." He said, "I know a diesel engine when I see one, I've been a mechanic for 25 years and I know what I am looking at, those are fuel lines!". He had already paid me and was taking it to Texas, so I said, "Have a safe trip!".

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Re: Spark plug wires

Post by AFM38A1 » Tue Dec 07, 2021 12:12 pm

My newly purchased M38A1 has metal braided wires.
The MV tech said they were aftermarket from the Philippines.

They look in good shape. Their only sin is being metal colored and not black.
Given the price of new wires, I was planned my on keeping them.
Any comments or suggestions?
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All stock w/factory V-8. Used as a daily driver for 7 years.

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Re: Spark plug wires

Post by W. Winget » Tue Dec 07, 2021 12:27 pm

Relax, not all issue wires have the outer abrasion rubber on them either..
So good news...
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Re: Spark plug wires

Post by Jim Thomason » Sun Jan 02, 2022 12:53 pm

Years ago I fabricated a set of spark plug wires using second hand wires from an aircraft engine, (there are two sizes---jeep uses the smaller one). The spark plug end was correct for the jeep spark plugs and; once cut to length I adapted the distributor end onto the original distributor screw on connectors. These aircraft wires are supposed to be replaced at each overhaul and usually are in "like new" condition. If you have a small airplane airport local check them out or search the web. Not the best solution for all -- but another option. For me it was at zero cost. Jim


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