Spark plug wires...7mm vs 8 vs 8.5 ....

[dogma420]

Just wondering any thoughts at all...

I will need to get some new spark plug wires soon, and was wondering thoughts on which size I should get--I'm looking at about $15 difference between all 3 sizes of wires from where I'm looking, so price doesn't matter.

I have a 72 240, original motor...in the spring I'm going with a 81 ZX Dist and a good output coil, so I have a real good spark--this is a weak area on my motor--as I foul my spark plugs due to weak rings. Trying to squeeze a little more time out of her.

Anyways, my car is nothing special on performance...my only hop-up part is a stock replacement K+N air filter. No header or cam...when I rebuild probably get that stuff done...

What width spark plug wire would be recommended for my car for the electronic dizzy with a high output coil?

7mm, 8mm, or 8.5mm?

I assume that stock size is 7mm, but I was wondering about the 8 or 8.5...are those overkill for my situation, or is more always better if they are the same price?

Thanks for reading my post.

[d240zx2]

Hi, Dave. You may presume I'm no electrical expert. But I do know that all electric current travels on the outer surface of its conduit. Since a larger diameter wire has more surface area with which to conduct the current, I'd go with as large a wire as is available.

FWIW,

Frank

[Arne]

Except the size that is listed is the size of the insulator, not the conductor. Larger wires have more insulation, and therefore more of the spark makes it to the plug, rather than leaking out on the way. For a car with a normal ignition, there is really not much difference between the sizes, unless you have an incredibly hot coil. I'd go with whatever good name brand looks good to you. I've got NGK 7mm on my red car, they seem fine, and I've observed no spark leakage after dark.

[240ZMan]

I read an article some time ago that I can no longer find that compared the distance over which the spark could jump as a measure of how well the wires conducted the energy from the coil to the spark plug. What I remember is that the Taylor and NGK were both about equal, and given the NGK are usually cheaper, they are the better deal. There was one brand (name escapes me again) who was significantly better but started at around $100 per set. Everything else tested in between those end points was not worth it. If anyone else has this article, please post the link.

One key point was that the "size" of the wire did NOT correlate to the energy of the spark. There was at least one 8.5 mm that was no better than another 7 mm. As with everything else in Zs (and life), the bigger item isn't always the better one.

It's my understanding that some of the benefit of a premium wire is that the insulation material can withstand higher temps over a longer period of time. I have never seen any tests that validate this though.

FWIW, I used to adjust my timing by grabbing the top of the distributor cap and turning it. Since I've upgraded to an MSD 6AL and Blaster coil, I no longer do that I'm running a set of NGK that are about 4 years old now. Probably time for me to replace them.

To go back to the original question, unless you plan to go crazy with a very high energy ignition system, the NGK 7 mm wires are probably the best value.

[RoadZter]

I would also look for wires with low resistance. A good set should measure below 1,000 ohms of resistance (per foot). I recently checked the resistance of some basic sets (IIRC they were Bosch from AutoZone) that had over 4,000 ohms of resistance! By comparison, a set of 8mm Accel's only had about 750 ohms of resistance - huge difference!

[ktm]

"There was one brand (name escapes me again) who was significantly better but started at around $100 per set"

Probably Magnecor. I am running a set of custom made set of Magnecor wires on my car. They came to approximately $80.

The Magencor wires are GREAT if you are concerned with the spark signal interferring for your EFI (which is why I bought a set and those running Megasquirt also buy them).

[240ZMan]

Magnecor is the one I couldn't remember. Thanks!

[dogma420]

magnecors were the ones I was talking about...7mm are like $110 up to $120 for 8.5mm...

I just picked up some 7mm NGKs and if I really want to spend the money in the future, I might end up getting the magnecors, but I don't think they'd make a difference unless I went MSD or Crane electronic....

Thanks for the replies everyone!

[240ZMan]

Like KTM said, the main benefit of magnecor would be they emit less RF energy and hence are less likely to interfere with an aftermarket fuel injection setup like megasquirt. Before I started my MS conversion I looked around and found a few shops on the web that sold magnecors for about $80. But so far I haven't had any interference so haven't bothered to spend the extra. If you're not having issues with the NGKs, then like me, I'm sure you could find better ways to spend $$$ on your Z :laugh: