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My '84 F250 (351W) had been running a little rough lately, so I thought I'd try a tune-up. Lo and behold, I found 3 (!!!) plug wires broken. All three were broken at the crimp inside the boot at the plug end. I removed them very carefully, using special pliers on the boots. I did not pull directly on the way. In all my years of wrenching, this is the first time I've ever had one fail like that, let alone three. That has me wondering what was the common factor.
The plug wire set was from Standard Motor Products, installed about 2.5 years ago. I've only put maybe 10,000 on the truck since then, but most of that was working hard, hauling a camper.
At the time, I had installed a set of plug boot heat shields, as seen in the picture. Note the white area, caused by heat from the exhaust manifold. None of the boots themselves showed any obvious heat damage. Has anybody here used this type of heat shield? My hunch, subject to medication levels, wind direction, and the nearby presence of squirrels, is that the heat shields actually trapped heat inside and caused an early breakdown.
It may be expensive, but I always buy Motorcraft ignition parts (cap, plugs/wires, rotor), they always seem to last for ages
Agreed, but I couldn't find a good Motorcraft number for my application. It's an '84 F250HD, 351W w/ Duraspark, engine VIN code G (2 bbl). Any got a valid number? I've got a Motorcraft cap and rotor.
I've got an AC Delco set of wires on order in the meantime.
The problem I have found, the boots are not stuck to the wire very good. So when you pull on the boot, the boot slips up the wire and you really are pulling on the end at a bad angle, which tends to break it. And also they seem to crimp the ends so hard they almost cut the end of the wire off. If the boot was stuck better to the wire itself, then it would support the end better when you pulled it off.
You can fix it by prying the end apart and taking it off the wire, re-stripping the wire and re-crimping it. The key to the whole thing is once you put them on, don't take them back off. Great product right?
The key to the whole thing is once you put them on, don't take them back off.
Yeah, that seems about right.
I can't remember if I had previously removed these plug wires, but am thinking I had not. I'd have to say these were failed BEFORE this latest removal. The truck was running rough and then was fine after replacing the set. I can't be 100% positive, because I also replaced the spark plugs at the same time, but none of them showed any signs of damage.
So what's the consensus on adding heat shields over the boots? Do they help? Do they concentrate heat and make things worse? I left them off with this new set of plug wires. The engine originally had some thin sheet metal shields, but they had long since rusted away. Maybe I should just fabricate something like that.
04-23-2018, 08:03 PM
