DIY Spark Plug Wires - Build Your Own Plug Wire Sets

Place a boot (without the metal terminal) over the appropriate plug on the distributor. On an HEI such as this, the coil keeps you from running the wires across the top of the distributor, so make sure you can route the plug wire from the proper direction. Mark the wire, not at the beginning of the boot, but directly over the distributor plug.

You can cut the plug wires with standard wire cutters. You will need to leave enough of the conductor wire to fold underneath the terminal, so make your cut an extra half-inch longer than your original mark.

Don't bother trying to strip your plug wires with a razor blade; you will only end up with a hack job. Instead, invest in a plug wire tool such as this. It handles stripping the wires and crimping the terminals and does a great job of both. This one is from MSD, but most ignition companies offer their own version.

The stripper portion of the tool cuts through the jacket without harming the conduction wire. Use it to strip away approximately one-half inch of the jacket.

Fold the exposed portion of the conductor wire back over the jacket and install the correct metal terminal so that the back of the terminal covers the conductor wire. (The open portion of the terminal that gets crimped into place is opposite the conductor wire.) This is how the electricity gets from the plug wire to the terminal.

Now use the crimping portion of the tool to crimp the terminal band over the plug wire. I've found it's usually easier to install the terminal into the tool and then slide the plug wire into place.

Here's a terminal after it has been crimped onto the wire. Notice how the ends of the terminal band have actually dug into the silicone jacket of the wire to provide a slip-free grip.

The part that usually leaves most racers cussing is getting the protective rubber boot over the terminal. It must be a tight fit to keep dirt out which makes it nearly impossible to get the boot in place without a little help. Different people use different lubricants, including non-stick cooking spray, but Mallory's tech department provided the best tip. Try standard brake cleaner. Spray it liberally on both the wire and inside the boot, and the boot will slide right on. Plus, the cleaner dries without leaving a residue that can impair conductivity.

After all the wires are assembled, don't forget to test fit, complete with the distributor cap in place, if yours has one.

Before the final install of the plugs, use a little dielectric grease on the ends of both the plugs and the distributor. Mallory includes a couple packs of grease in each kit just for this purpose. The grease helps ensure excellent conductivity between the terminals and the plugs, and keeps the terminals from galling to the plugs.

Although the 8.0mm jackets are usually enough insulation to keep the wires from cross-firing, it is still a good idea to secure the wires so that there is an air gap between them. Wire looms are good for this but when thrashing on the car in the pits they can often get lost. Instead, make your own out of zip ties like this. Use one zip tie around all the wires and then secure more between the wires to hold them apart. Now, when working on your engine in a hurry you can cut the loom off and then make a new one instead of hunting for the one that dropped in the dirt somewhere.

The finished project only required an hour or so and suits our needs perfectly. It is hard to see the wires in this photo because they are tucked out of the way, but that's exactly the point, isn't it?