Spark plug wires are the highway that electricity travels on from your ignition to the spark plugs in each cylinder of your engine. That highway needs to be a certain size and length — the problem is that not every application has a direct-fit spark plug wire. In this video, Jeremy Stoermer from Holley shows us how to make a custom set of spark plug wires to fit any application.

Custom spark plug wires allow you to route the wires exactly where you need them to be; the wires might have to be routed in a specific way to avoid the vehicle’s exhaust or be positioned to work with a custom mounting location of your ignition coils. After you’ve determined you need to create a custom set of plug wires, you’ll want to see what style of plug boot end is needed, and make sure you also have the right ends for your distributor or coil. The wire you select needs to be sized correctly for the amount of spark for your engine.

If you decide that making your own plug wires is something you can do, you’ll want to get the right tools and supplies for the job. A crimping tool of some kind is a must-have item to make sure you secure the terminals to the wires properly. You can pick up a ratcheting-style crimp tool, or one that fits in a vice that can crimp the terminal onto the plug wire. Dielectric grease is another item you’ll need to make your own spark plug wires — this helps with assembly and prevents voltage leaks.

The video that Holley put together does a great job explaining how to build a set of spark plug wires, what the different types of terminals are, and the most common ways to assemble the plug wires. If you’re looking to build your own spark plug wires, this is a must-watch video.