Technical 7mm versus 8mm spark plug wire

What is the difference between 7mm and 8mm spark plug wires. Is it just the thicker external silicone cover or is the protected spiral core wire actually larger and better able to pass current with less resistance? If the 8mm is better, any suggestion about the best brand, e.g., Taylor, Accell, etc.?
Thank you.

 

As far as I know, just thicker insulation - which never is a bad thing in high voltage applications. Resistance is of relatively little importance at high voltage and low current, on the other hand.

 

1mm

 

What’s an mm???

 

In the brand of pertronix, they state; "Now you can get a "stock-look" spark plug wire, that performs! We've designed our 7mm wires with the same core we use in our 8mm wire. The only difference is the 7mm flat black silicone jacket that hides its performance potential from the naked eye. Get the best of both worlds with "state-of-the-art performance and a stock look". These wires will fit most original wire looms. Select a custom tailored set for a great out of the box fit or a universal kit to match your unique engine and wire loom configuration. FEATURES • Two current paths for reliability and redundancy. -Primary path: Spiral wound stainless steel alloy. -Secondary path: Carbon impregnated fiberglass center core. • Low 500 ohm per foot resistance. • 7mm Silicone jacket to resist high temperatures, moisture, oil and chemicals. • EPDM (Ethylene Propylene Diene Methylene) inner insulation for superior heat resistance and prevention of arcing and voltage leaks. • Fiberglass reinforcing braid for added strength and flexibility. • Lifetime Warranty."

 

Millipede?

 

If the Pertronix claim is accurate, it sounds like the one millimeter difference between the 7mm and 8mm wires is more than just the thickness of the silicone cover but the actual spiral core is different (better). Does anyone know that claim to be true? Thank you.

 

I put 8mm Accel wires on my slightly OT Cadillac and seriously could not tell any difference from the old stock ones. Maybe it makes a difference at 7,000 RPM, but I haven’t tried that.

 

One thousand microns.

 

Try 8.8's, that will put you over the top!

 

In normal Hot Rod driving as most of us do , the thing that will feel different is your billfold will be lighter from cash flowing out . If you maintain your car as a piece of mechanical equipment and not a looker trophy , 7mm wires will do the job until the cows return home . The difference between 7 and 8 mm is nothing more than a look on a street driven car . 8 and 8.8 mm you see on a drag car are solid ( braided ) core wire , much different than most of us will be ever using on our street driven cars for . Packard 440 wire was my go to only for years , not fancy colored , not fancy looking but copper core guality stuff that I never had to worry about .

 

Easy !! Candy that hot rodders eat.



See ?

 

Let's go just below the surface of this claim a bit. I believe Pertronix offered the 8mm wires first. What if the core in those was no larger that the typical spiral wound 7mm offered by other vendors? Now they introduce the "new improved" 7mm and can rightfully make the claim that the core is the same as in the old 8mm wires. The end result may well be that they are no better or different than any other 7mm spiral wound.

People who write advertising are pretty good at creating copy that may well be true, but creates an impression that may not be.

I am an asshole that always tries to read between the lines.......

 

I am trying to figure out what fits in the old Mallory dual point flat cap distributor. 7 mm with standard crimps doesn't

 

Actually only 0.019685 from the core.

 

7mm

8mm

 

Just shy of .040 difference.
The outer casing of 8mm plug wire can be difficult to fit in wire separators designed for 7mm wire.

 

According to the Pertonix, Accel and Taylor ads, the 8mm spark plug wires have a better quality core that carries more current and requires improved, larger silicone covers to avoid electrical interference or leaking which can affect electronic equipment.

 

No crimps on end...lose them...just plug wire..make sure you have the rubber piece (F) between the two halves so it retains the plug wires

 

Very cool and thanks.
So much to do I haven't had time to look at it close. Do you strip a tad so to touch the contact?
The rubber and the 2 cap halves act as the strain relief....excellent

 

Well, after four years you've probably gotten an answer, right? If not, make a clean cut, no stripping, and push the end of the wires down over the pins, then tighten the cap a bit to capture the wires in the rubber retainer.

 

And nobody mentioned the fact that there isn't a "F" in the diagram !

 

Yes there is...

 

Took a second but I found the F

 

Look into the cap, it’s labeled, not pointed out.

 

Somebody in the armed forces should be able to tell you.

 

They're little round candies that melt in your mouth not your hand!

 

Nope, they only use mm's in metric countries, like Australia.

It's a millimeter, which is a tool used to very accurately measure millipedes. If you want to measure centipedes, then you use a centimeter.

No idea how they measure bugs in countries that use imperial measures.

Cheers,
Harv

 

I do believe that stands for monkey motion