What size spark plug wires?

[JL1RX7]

Ok I have used for years the 8.5MM Magnecor wires on my other 7's. It is about time for replacement for my verts NGK's. So my question is whether to go with the 8.5's or the 10mm's. Also not about not trying something new and cost is not an issue. So thoughts comments etc.....

[RETed]

Size doesn't matter...in this case.
The only thing those dimensions are good for are for insulation.
Unfortunately, current leakage (i.e. arcing) does not usually initiate from the wire insulation itself - it's usually from "seams" or the boots.

"Thicker is better" is a good advertising slogan for the spark plug wire manufacturers.
You might have a case when dealing with domestic (V8's) where some spark plugs are located very close to very, very hot exhaust manifolds - the spark plug wire insulation works both in electrical and heat insulation.
With the location of our spark plugs on a 13B, heat is not really an issue.
A good, quality thinner (i.e. 7mm) insulation is going to always work better than a poor, thicker (i.e. 10mm or bigger) insulation.

Personally, I use MSD Super Conductors (in the generic V8 kit).
I get two sets for a 13B, and the price comes down to about $50 per engine.
I can cut them down to whatever lengths I want, and I already have an expensive MSD crimper that takes care of all the termination.
Options are either for red or black - I have the black ones.

Another thing to be wary about...
Resistance specs...
Manufacturers like to tout how LOW their wire resistance is...
It really doesn't matter.
The air gap at the spark plug is measured in MEGA ohms - that's 1,000,000-ohms.
Resistance is serial, so all the little bits add up.
(I'm even disregarding the resistance of the spark plug itself, since most of us run "resistive" spark plugs for EMI suppression.)
Even though NGK stock replacements are usually over 1,000-ohms per wire, adding the resistance of the air gap practically negates that resistance.
Even though your aftermarket wires might be a palty 10-ohms, the air gap still outweighs that by a LOT.
Bottom line, spark plug wire resistance is moot.


-Ted

[JL1RX7]

Thanks ted for the info. I know I have read the spec's on resistance and coming from electronics in the military can very under the lower the better. But It comes at a cost of EMI, so that is the biggest issues. I never considered the air gap in the resistance issue. Good food for thought!