I currently have radio interference, how do I identify interference coming from ignition wires?
Magnecor Race Wires, if properly fitted, will provide excellent RFI suppression indefinitely for virtually all vehicles in which the original carbon conductor ignition wires provided adequate suppression. In severe cases, such as those experienced by mobile ham radio operators, where carbon conductor ignition wires (original and/or aftermarket) provide RFI suppression only for a short time before replacement is again needed, we recommend the use of our CN Series Race Wires, the only ignition wires capable of indefinitely suppressing severe RFI without reducing spark current!

The majority of original equipment and aftermarket carbon conductor (suppression) wires will provide adequate RFI suppression until the wire conductors’ limited suppression life is exceeded. Unfortunately, for mobile ham radio operators in particular, the effective RFI suppression life of most carbon conductor ignition wires is less than that required by anyone listening only to signals received on commercial AM and FM broadcast bands.

No spiral conductor “pro” etc. ignition wires sold in mass-merchandisers and speed shops will provide adequate (if any) RFI suppression for Ham radios, TV and sensitive sound equipment. Most provide token RFI suppression by coating the spiral conductor with a conductive latex or silicone compound, which, like a carbon conductor, is only effective for a limited time — see: Truth About Ignition Wire Conductors.

A guide to identifying radio-interference noises caused by ignition wires:

Often, we are asked to describe how broadcast band noise can be identified as coming from ignition wires. Although it’s hard to describe in words – On the AM band, noise coming from spark plug wires is usually heard as a sharp “clacking” noise (from speakers) at idle that increases with engine speed to a “ZZZZ” sound at higher rpm. A faulty coil wire will always create a “ZZZZ” noise. A faulty or inadequately grounded antenna lead, or a heavily corroded antenna body can also cause the same sounds, even with good wires, because the antenna can’t adequately pick up the radio signal.
On the FM band, if you hear a ticking noise that increases with engine speed, it’s more than likely that somewhere in the ignition system a spark is jumping to ground, or a spark is jumping a large gap inside a carbon conductor wire with the conductor burning back from the metal terminal. Loose or badly fitted spark plug and coil wires, wires burnt through from header or turbocharger plumbing heat, ignition coil or coil packs with cracks in towers or bodies, cracks in distributor caps and failed or excessively worn or gapped spark plugs (causing sparks to come out of spark plug boots and connectors) all can create open sparks that can be heard on the FM band.

It is important to note that our CN Series Race Wires will not always solve extreme RFI problems caused by radio set and/or antenna shielding, grounding and positioning problems. The same goes for problems caused by other ignition components and failing or excessively gapped spark plugs fitted into aluminum cylinder heads. Sometimes, using extremely high resistance carbon conductor wires or in-line resistors can hide extreme RFI problems, however, the resulting weaker spark will affect engine performance and fuel economy. Generally, if our CN Series Race Wires are not able to provide sufficient suppression, the underlying cause of the problem will have to be rectified, as these wires are designed to provide the maximum allowable suppression before loss of spark energy occurs.

WARNING about metal shielded and so-called “Built-in Capacitor” ignition wires:
Although using a grounded metal shielding over the entire length of each ignition wire will certainly provide RFI suppression, and this style of wire is still used on low-revving piston driven aircraft engines, it is common knowledge (from experience) amongst automotive electrical engineers that it’s unwise to use ignition wires fitted with grounded metal shielding over ignition cable jackets on a high-revving automobile engine — as the problems caused by any style of ignition wires which need to be grounded have proven to be so great, that using them should be avoided at all costs!
This type of ignition wire forces the cable jacket to become an unsuitable dielectric for a crude capacitor (effect) between the conductor and the grounded braiding. While the wires function normally when first fitted, the cable jacket under the metal shielding soon breaks down as a dielectric, and progressively more and more spark energy is induced from the conductor (through the cable jacket) into the grounded shielding, causing the ignition coil to unnecessarily output more energy to fire both the spark plug gaps and the additional energy being lost in the grounded metal shielding. This situation leads to engine power loss, and eventually to ignition system overload failures as the insulating ability of the cable jacket (under the metal shielding) breaks down.
Ignition wires promoted as having “built-in capacitors” are nothing more than solid wire or spiral conductor wires over which grounded metal shielding is fitted to only part of the wires’ insulating jacket. These wires have all the disadvantages of wires with grounded metal shielding over the entire length of each ignition wire — without being able to properly suppress either RFI or EMI!