Spark Plug Wire Replacement

[SPF Required]

I will be doing some maintenance next weekend including new distributor cap, rotor, and plugs. My question is should I also do the spark plug wires at the same time? How long do plug wires last??

Thanks for any knowledge you are willing to share.

 

[Boydsdodge]

How long have they been on, miles/years?

 

[Imperial_Eagle_72]

They could last forever, but they will leak voltage. I would think typically 5-6 years on a daily driver.

 

[SPF Required]

Thanks for the quick input. While they are a few years old at this point, they do not have a lot of miles on them (weekend cruiser car). I will start with the more affordable stuff as planned, and hold off on the wires.

 

[Big_John]

I will be doing some maintenance next weekend including new distributor cap, rotor, and plugs. My question is should I also do the spark plug wires at the same time? How long do plug wires last??

Thanks for any knowledge you are willing to share.

There is a resistance test in the FSM. You have to have a meter that will measure 50K ohms at minimum and that means the $10 Harbor Fright version won't cut it.

The other two tests are visual and probably tell the story more than testing resistance. First is obviously general condition with attention to the terminals. The second would be to check visually for leakage and that just involves opening the hood in the dark while the car is running and looking for sparking to ground or another wire.

The most wear you can put on plug wires is handling them... and we've all seen guys grab the wires and yank rather than pulling them off at the boots.

If they look good (pass the visual tests), have a history of not being manhandled and the car runs well, I'd leave them alone.

 

['66 Fury I]

If there has been any possible leakage at the terminal/boots, the boots could have carbon tracks in them. In this case, replacing plugs and cap could lead to continued leakage and carbon tracks on the new plugs/cap. Then new wires could become carbon tracked from the plugs/cap. I would replace it all at the same time. I got caught on that many years ago. Just my five-cents-worth! Lindsay

 

[1970FuryConv]

Thanks for the quick input. While they are a few years old at this point, they do not have a lot of miles on them (weekend cruiser car). I will start with the more affordable stuff as planned, and hold off on the wires.

When I was in tech school long ago, this was the guideline for resistance.

Normal Resistance: Max of 3K-12K ohms per foot, or 30K ohms per wire

 

[Big_John]

When I was in tech school long ago, this was the guideline for resistance.

Normal Resistance: Max of 3K-12K ohms per foot, or 30K ohms per wire

1970 FSM says under 30k ohms for wires less than 25" long and 50k ohms for over 25" long. They also check at the inside of the distributor cap with the wires connected, which I find interesting because then it really checks the integrity of the terminal connection to the cap too.

That said, if you stuck with 30k ohms for everything, you can't go wrong.

 

[SPF Required]

As usual, thank you all for the knowledge share. This is all extremely helpful!