Next up for the Circle Track...
Next up for the Circle Track dyno mule is a pretty hardcore test of several different header designs. For this we had specific needs for a set of plug wires that would work on a dyno with several different styles of exhaust headers, which required cutting our own set of plug wires.
No two racecars are exactly the same. We all have our own little quirks or favorite ways of doing things that make even tube-frame cars from the manufacturer a little bit different. Changes to the front clip, the way accessories are mounted to the engine, your headers, the steering shaft and many other factors can affect the best path for routing your plug wires from the distributor to the spark plugs. Sometimes, a standard set of plug wires just cannot be made to fit correctly. That's why several performance ignition companies sell cut-to-fit plug wire kits.
Typically, a do-it-yourself plug wire kit is boxed with the spark plug terminals and boots already attached to the wires. The wires are already cut to approximate lengths but are left long to allow for different routing options. Also included are loose terminals and boots for the end to be attached to the distributor. Usually, an extra length of wire and boots is included for the coil as well. When ordering your wires, you need to be able to specify whether you need straight or angled spark-plug boots and the type of distributor you are working with. The style of plug boot is usually determined by your cylinder heads and headers. Cylinder heads with straight-cut plug holes (stock-style) will almost always require angled plug boots in order to avoid contact with the headers.
We recently ran into the need to cut a new set of plug wires for Circle Track's dyno mule Chevy 350. During the last dyno thrash a couple wires had been pulled loose from the terminals (It turns out people don't want to reach behind hot exhaust headers to pull plug wires loose from the boots) and another had been left loose and gotten burned against a header tube. So the set was discarded and we started fresh. Here's a few tips we've picked up over the years. If you have any of your own after reading this, please write in and share them with us in our "Readers' Tech Tips" section.
 The standard ignition for...  The standard ignition for our dyno mule is a Mallory HEI high-performance unit, so we stuck with Mallory for the wires, too. This is a set of Mallory's 8.0mm Pro Sidewinder wires. Two sets of boots and terminals are included, but I only photographed the set I planned to use. Unfortunately, I realized right after this photo was taken that the straight boot design for the spark plugs would contact the headers. See, even magazine guys make mistakes. |  A quick trip to my favorite...  A quick trip to my favorite speed-parts store landed me this Mallory wire set. These are Mallory's Sprint Wire Pro Wires. Like the Sidewinders, they are 8.0mm but do not have a stainless alloy wire wrap as part of the conductor. Both types of wires are available with either a straight, 45 or 90 degree plug boot and several different types of boots to fit different distributors. |  The most important thing before...  The most important thing before you even unbox your plug wires is to be able to correctly identify your engine's firing order and cylinder numbering system. There are no do-over's once you start cutting wires and crimping terminals, so it is a necessity to get it right the first time. On race engines, plug wires and distributors are constantly being removed. Save yourself the chance of making a mistake and go ahead and number all eight plugs on your distributor. It may look a little amateurish, but it is still a lot better than trying to start a race with a bad miss because you've gotten two wires crossed. |
 It is also critical to make...  It is also critical to make sure how your cylinders are numbered. For example, on Chevrolets, the right bank of cylinders are all odd numbers while on a Ford Windsor the number-one cylinder is on the left bank and is numbered one through four while the right bank is five through eight. On both, the distributor rotor turns clockwise. Here's the standard Chevrolet firing order and numbering sequence. |  This is the standard firing...  This is the standard firing order and numbering sequence for a Ford Windsor. |  You can help reduce the chances...  You can help reduce the chances of a plug wire pulling loose from the spark plug terminal by adding shrink wrap over the end of the boot and the first inch or two of wire. Most manufacturers sell pre-cut shrink wrap for this purpose, but I use stuff my local speed shop sells for insulating battery cables because it is thick, works just as well and-most of all-it's cheap! At the bottom of this photo is a plug boot right out of the box. In the center is a boot with a short length of shrink wrap slid as far up over the boot as I could get it. And at the top is a boot and wire after the shrink wrap has been heated until it has shrunk into position. |
 The correct way to fit shrink-wrap...  The correct way to fit shrink-wrap tubing is with a heat gun, but like most racers, I don't have one. You can go old school with a lighter, just make sure to hold your plug wires out of the flame. Be careful not to burn the silicone jacket covering the plug wires or the boot. |  The plug wires are cut to...  The plug wires are cut to several different lengths. Test fit them all before you begin cutting to make sure they will work with the routing you want. In addition, all should reach the distributor with some extra length to spare. Rearrange the wires and the routing until you get the best fit. |  Instead of routing the wires...  Instead of routing the wires between the header tubes, for Chevrolets, the cleanest solution is usually to run the wires alongside the cylinder head to the back of the engine as you see here. |