If you are experiencing a high end miss or rough idle, don’t jump to the conclusion that your ignition box or fuel system is failing. Many times it can be as simple as a poor connection, bad plug wire or other problem within the secondary part of the ignition system.

Spark plug wires have two main objectives; deliver as much voltage and current as possible to the plugs while minimizing the amount of Electro Magnetic Interference (EMI) that the flow of electricity radiates. However, there are plenty of variables that make the plug wire’s seemingly simple task more difficult.

Exhaust temperatures, underhood vibrations and winds, chemicals, moisture and debris all hinder the plug wire’s performance. Fortunately, many of these problems can easily and economically prevented.

One of the first things you should check is the resistance of each wire. This is a simple task and an ohmmeter is something most racers already own (or should own). Spark plug wires from different manufacturers have a variety of resistance specifications, so be sure to check with the manufacturer of your wire as to what the resistance per foot should be. A rule of thumb would be around 500 – 1,000 ohms per foot with several exceptions. Wires with over 1,500 ohms per foot can exhibit significant losses in terms of voltage delivered to the plugs.

One of the exceptions is solid core wires, which are not recommended for cars with performance ignitions or other on board electronics. Solid core wires create enormous amounts of EMI which will interfere with the ignition, tachometer and other electronics on the car. Another exception is the MSD 8.5mm Super Conductor Wire. This wire has only 40 – 50 ohms per foot of resistance; however it suppresses EMI like a 1500 ohm wire!

When measuring resistance, remove the distributor cap, leaving the wires connected, so you can check the resistance from the terminal of the cap. This kills two birds with one stone. Make sure the terminals are making good contact and do not hold the terminal in your hand as your body’s own resistance will add to the value of the wire. Be sure to move and bend the wire around with the ohm meter attached. This will help locate any intermittent problems in the wire. (Remember to divide the resistance value by the length of your wire in feet.) Usually, a bad wire will show a significantly higher resistance value than the rest of the wires.

It is important to visually inspect the sleeve and boots of the wires for cracks, burns or melted sections. If any problems are found, the wire should be replaced. If you can, inspect the terminal and the crimp on the wire. The crimp should be secure without cutting into the sleeve and in most cases, the conductor should be clamped between the terminal and the sleeve of the wire. MSD Ignition now offers a special Dual Crimp Terminal so the conductor doesn’t need to be bent over.

These special terminals have two sets of crimp tabs. One set secures the terminal to the sleeve of the wire while the other set of crimp tabs grasp the conductor itself. This way the conductor does not have to be bent 180 degrees over and pressed between the wire and terminal which creates a prime spot for voltage leaks.

For added protection to the wires themselves, a heavy duty heat sleeve is a good idea to add to your wires. MSD offers a Pro-Heat Sleeve and a Boot Guard for extreme heat cases. The Sleeves feature a glass woven sleeve with a thick, silicone outer shell that protects against heat, abrasion and chemicals. The Boot Guard is extra thick and is made to handle extreme temperatures near the headers or manifolds.

Also, keep in mind that a bigger spark plug gap and higher compression are things that tax your spark plug wires along with the cap and rotor. The larger gap creates more resistance and in turn more heat in the wire as it needs to send more voltage to jump across and ionize the plug gap. MSD Ignition recommends increasing the plug gap by .005” – .015” with their Ignition Controls, but every engine is different. Some may see a big performance advantage with the larger gap, others may not. And, if you don’t see a performance gain, go back to the smaller gap and make life longer and easier on the secondary part of the ignition system!

There are a lot of steps you can take to ensure that your wires deliver race winning performance as well as endurance. A minor investment of time and dollars should be in a set of wire separators. Not only do they keep the wires away from header heat and sharp edges, they keep them secure. At track speeds there is a lot of wind which can actually whip the plug wires away from their connections!

When installing new wires, a drop of a dielectric grease, such as Spark Guard from MSD, is a good idea. A small amount of this grease will help isolate the voltage, make removal of the wire easier and keep moisture from building up in the terminal.

Less resistance in a plug wire means more current flows to the plug which is exactly what we want. However, lower resistance also means more Electro Magnetic Interference is radiated from the wires. This EMI will interfere with other electronic controls on the race cars, which is not what we want.

With this, racers have always had to settle on a wire with “fair” resistance to guarantee that EMI is suppressed. Now there is an alternative.

MSD’s 8.5mm Super Conductor Wire has only 40 – 50 ohms per foot of resistance, yet suppresses EMI like that of a 1,500 ohm wire! They do this by combining a copper alloy conductor with a special center core and winding procedure. The conductor is wound so tightly around a special center core that there is 40 feet of conductor wound into a foot of plug wire! This winding combination produces an EMI “choke” inside the wire giving you the best of both worlds!