Spark plug wire life

[Ted Idlof]

How often to replace and how do you know?

I get conflicting opinions on spark plug wires and how often to replace. I see DW said awhile back to replace them as one way to track down any hint of power loss. Others think they should run a long time with no power loss since we have such a low mileage condtion compared to street usage.

What do the FM gods here think?

[JRMarchand]

Ted

those are some of the sturdiest ignition leads out there. I've seen the boots go from gray when new to a faded light brown tan color after 10+ seasons.
I think the Gods would say up to five seasons is safe.

[sracing]

I am not sure how anyone could come up with a "rule of thumb" for plug wires. There are cheap solid and resistive cores, There are expensive solid and resistive cores.

Most common problem with wires is a insulation failure. Less common is a open circuit.

If they are chaffed, cut, abrased, etc. replace them. Neither like having bends in them that are to sharp. Obviously the ends can come loose when un-installed and re-installed enough.

At peak cylinder pressures (higher end of the RPM band under load) the coil voltage is highest. This is the point where the voltage can arc through the insulation. Thus a complete missfire. An open/high resistance in the wire can decrease the available voltage to the plug and even cause some spark timing flutter. (Something you won't notice, but can decrease peak HP).

Wires are cheap compared to a per lap $. If you have ANY symptoms, replace them. If you don't have any symptoms, I would say a 3-5 year replacement plan is fair. By examining the condition of the wires and your pocketbook you can determine if it should be earlier.

[driver68]

The wires are pretty good but we have chased arcing through the boots at the distributor cap that may be a function of age. We now switch every other season. So, watching for arcing is on the lengthy checklist of things when warming the car in the shop before we head out.

[Ted Idlof]

for your comments; all good info. They do seem to be quite sturdy and reliable, but I'll be replacing based on age (9 years, ) just to be sure I won't have to worry about that issue.

[Raceworks]

I've never had any issues with the spark plug wires. Probably the most common problems I've had were plug fouling before I got the jetting right, worn out distributor caps & rotors, bad MSD boxes, and coil failures (in that order). That being said, I don't think I've run more than 4 or 5 seasons on a set of wires.