Time for new plug wires?
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 878
Likes: 60
From: Minneapolis, MN USA
Time for new plug wires?
Hi All,
My understanding is that spark plug wires should be changed if they are all not consistant on an ohm/ft reading...is that correct? Regardless of what the ohm/ft reading is, if they are not consistant, then they should be changed (as opposed to just comparing the actual resistance in ohms, regardless of the length of the wire). I just checked mine and got the following:
#1 - 6,181 ohm/ft
#2 - 9,904 ohm/ft
#3 - 10,889 ohm/ft
#4 - 9,434 ohm/ft
#5 - 12,658 ohm/ft
#6 - 10,021 ohm/ft
#7 - 7,952 ohm/ft
#8 - 8,423 ohm/ft
I'm guessing these are NOT consistent enough and should be replaced? Particularly there is a 2:1 factor between #1 and #5. Do you all agree that this is a wide enough difference that I should replace the wires? Or does it need to be an order of magnitude different?
Assuming I need new ones, it appears that Taylor are highly recommended, and I was looking at 8mm. I looked at Summit Racing site and the Taylor are quite a bit more expensive than other brands? Are they worth it? Regardless of the brand, should I be looking at the "Spiro wound" or "Spiro Pro"? My car is the 350/350 with stock ignition.
Thanks for the advice!
My understanding is that spark plug wires should be changed if they are all not consistant on an ohm/ft reading...is that correct? Regardless of what the ohm/ft reading is, if they are not consistant, then they should be changed (as opposed to just comparing the actual resistance in ohms, regardless of the length of the wire). I just checked mine and got the following:
#1 - 6,181 ohm/ft
#2 - 9,904 ohm/ft
#3 - 10,889 ohm/ft
#4 - 9,434 ohm/ft
#5 - 12,658 ohm/ft
#6 - 10,021 ohm/ft
#7 - 7,952 ohm/ft
#8 - 8,423 ohm/ft
I'm guessing these are NOT consistent enough and should be replaced? Particularly there is a 2:1 factor between #1 and #5. Do you all agree that this is a wide enough difference that I should replace the wires? Or does it need to be an order of magnitude different?
Assuming I need new ones, it appears that Taylor are highly recommended, and I was looking at 8mm. I looked at Summit Racing site and the Taylor are quite a bit more expensive than other brands? Are they worth it? Regardless of the brand, should I be looking at the "Spiro wound" or "Spiro Pro"? My car is the 350/350 with stock ignition.
Thanks for the advice!
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,562
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Those are some interesting numbers!
I have set #9508N wires and the show about 3 ohms per foot:
Wire # 1 2 and 3 are 49" long and show 13 ohms
#4 is 45' long and shows 12 ohms
5 and 6 are 32" long and show 8 ohms
7 and 8 are 28" and 26" and I didn't list the reading.
coil wire is 10" long and shows 3 ohms
My wires run down behind the engine and 2 on each side go through the boomerang.
Wire # 1 2 and 3 are 49" long and show 13 ohms
#4 is 45' long and shows 12 ohms
5 and 6 are 32" long and show 8 ohms
7 and 8 are 28" and 26" and I didn't list the reading.
coil wire is 10" long and shows 3 ohms
My wires run down behind the engine and 2 on each side go through the boomerang.
Last edited by Peterbuilt; May 29, 2015 at 04:29 PM.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
If you still have the shielding in place that runs down behind the engine mounts, a quick way to do the wires it's to pull the boot off the new and cut the old wire. Then tape them together so you can pull the new wire through. That way you don't have to unbolt the shields.
Racer
Joined: Jan 2014
Posts: 425
Likes: 3
From: Jefferson City Missouri
When in doubt, I would change them out. I've seen too many times issues caused bad wires, especially once you move them around after they have been sitting a while.
The OP looks like he has resistive wires while Peterbuilt has non-resistive wires. I have stainless steel non-resistive wires since I don't have any electronic to worry about and I don't listen to the radio. I want 100% of the energy to reach the spark plug.
The OP looks like he has resistive wires while Peterbuilt has non-resistive wires. I have stainless steel non-resistive wires since I don't have any electronic to worry about and I don't listen to the radio. I want 100% of the energy to reach the spark plug.
