Replacing spark plug wires probably won’t be the most glamorous upgrade you’ll perform this year, but it’ll help bridge a critical gap in the ignition circuit between great and poor performance.
While several wire manufacturers are available to choose from, this month we chose to use a set of MSD 8.5mm Super Conductor wires. If you check out the MSD catalog, you’ll find that it holds an extensive collection of pre-assembled and universal wires, including the classic red and the more subtle black versions.
For our small-block–powered ’67 Chevelle, we chose the red set with 90-degree boots (PN 31239, $95.95). Experience has shown us that the 90-degree boots are the safest bet, however, individual boots of other angles are sold if you run into a one-wire exception. The owner had already decorated the engine bay with red MSD electronics, so these wires would be right at home.
The ’67 started out with a set of MSD wires that were badly burned due to poor routing. To avoid a similar situation, we’re going to show you how to keep the wires away from danger, all the while producing an extremely clean look. Starting out with the universal set gives you the freedom to be creative in your routing design. With this freedom also comes the responsibility of assembling the wires correctly. MSD recognizes the potential difficulty of getting the correct crimp on the un-terminated ends and offer their own ratcheting stripper/crimper to handle the task. To further ease assembly, they also carry Spark Guard (PN 8804 $15.95) in their product lineup, which is dielectric grease that doubles as an assembly aid. It also ensures that you can easily pop a wire off the top of the cap down the road while keeping the voltage in and moisture out.
Rather than fitting each wire by marking, removing, assembling, and reinstalling it, we opted to install them once and crimp them while they were on the engine. This way we didn’t run the risk of not being able to re-create the same fit the second time around. With our sneaky under-header mounting, keeping track of which wires were which would be difficult without the numbered wire collars that are supplied with the MSD wire kit. One worry with universal kits is choosing the incorrect wire length for a particular plug, only to be stuck with a piece that was too short at the other end. By using the method shown here, there’s little concern for length because even the shortest wires were plenty long.
From the time we started disconnecting wires to pulling out of the garage for the test cruise, just over an hour had passed. It’s also important to note that the Chevelle came in with an intermittent miss that disappeared with the fresh set of wires. With the right tools and a plan, we gave this engine bay a new clean look and added performance at the same time.
The crimpers that do it all
The MSD crimpers aren’t just for assembling spark plug wires; it has several removable jaws for different connectors. Not looking to buy a new tool? MSD includes a crimper in each kit to use in your bench vise.
[01] This is our starting...
[01] This is our starting point. The owner obviously tried to keep things tidy but you can see where the wires are dangerously close to the headers, including where they have already been burned and later protected by a heat sleeve.
[02] Step one is the teardown....
[02] Step one is the teardown. Be sure to mark the number one wire on the distributor cap so you’re not guessing later. Also, when you start selecting wires for each plug, click on one of MSD’s numbered collars to keep them organized.
[03] We chose to route the...
[03] We chose to route the wires under the headers for an extra clean look. Each pair of wires (2 and 4 shown here) is positioned together. The rearmost wire gets a loop to change its direction, then both wires are secured with a zip tie. The loop action requires a longer wire so we used the two longest wires for the number four and three cylinders.
[04] There is no chance of...
[04] There is no chance of these wires touching the plugs with this routing method. The most important thing is to make sure your zip ties are tight and free from any header contact.
[05] To more accurately determine...
[05] To more accurately determine the length of each wire, we routed them one bank at a time. We anchored each side with one completed wire to let us mark the remaining three more precisely. We marked the wire at the point it would connect to the cap for reference.
[06] Assembly time! The first...
[06] Assembly time! The first step is to strip the wire. The MSD crimpers (PN 35051) have a stripper built-in. If you’re using the single-crimp method you will need to leave the core long as it will be folded back along the wire body.
[07] We’re using the double-crimp...
[07] We’re using the double-crimp method, where the wire body and wire core are crimped separately. The length of exposed core will be shorter to keep from protruding into the distributor cap receptacle.
[08] The MSD crimpers make...
[08] The MSD crimpers make it easy. Crimp it until it stops; this is your first crimp action.
[09] The second crimp secures...
[09] The second crimp secures the core; we used a standard crimper to press the terminal around the core.
[10] We experimented with...
[10] We experimented with pushing the boot on before the crimp and slipping them on after. By using MSD’s Spark Guard, it was easier to slip the boot on afterward. This may not be the case with socket-style caps; we have an HEI-style distributor cap that’s easily identified by its spark plug–like ends.
[11] Before clicking the wire...
[11] Before clicking the wire onto the cap, we added a touch of Spark Guard in the boot to help seal and make it easier to remove later. We did the same for the spark plug ends.
[12] We then completed this...
[12] We then completed this bank of wires with MSD’s Pro-Clamp wire separators. The second bank went just like the first, using one completed wire as an anchor to mark the rest.
[13] It almost looks as if...
[13] It almost looks as if we’ve done nothing at all—but that was the point. The spark plug wires are tucked away under the headers and sneak up to the distributor from behind the block. CHP