Whether you’re driving a classic car, or a high-output modern muscle car, ignition system upgrades have remained popular with enthusiasts for decades. In that time engine technology has improved dramatically and ignition systems have evolved as well.

One of the more popular ignition upgrades on both modern and classic muscle cars is the ignition coil. Whether it’s replacing the single coil mounted separate to the distributor, the HEI coil, a coil pack, or a coil over plug, we’ve proven on more than one occasion that coil upgrades do provide performance benefits including increased power you can see on the dyno.

We recently took a few minutes to talk to Steve Davis of Performance Distributors regarding some common misconceptions and myths about ignition coil upgrades. Our discussion brought to light several important points about ignition upgrades that the casual enthusiast may not have previously considered.

Higher Voltage Is Always Better -False

In the world of performance, more is almost always better. More boost, more airflow, more fuel, more horsepower, more performance, etc. However, more voltage does not always mean better in the world of ignition coils. Davis says, “The key is to maintain coil voltage under load -the acceleration phase, with little or no drop-off.” This is where Davis says it’s important to understand that a coil needs to perform consistently from idle through the shift point or redline.



The key is to maintain coil voltage under load -the acceleration phase, with little or no drop-off. -Steve Davis, Performance Distributors

The OEM GM HEI coils were an excellent example of this. Davis says that the OEM coils were notorious for drop off above or about 5,000 rpm. That might be ok for a half-ton pickup that never sees more than 4,500 rpm, but on a muscle car, especially one that’s been modified, losing voltage means lost engine performance, and not being able to take advantage of the engine’s potential modified or stock. Developing a better HEI coil was actually where Performance Distributors began in the ignition business many years ago.

Davis says the key to maintaining consistent voltage throughout the RPM range is in the internal construction of the coil. “We build our coils to use heavy gauge windings and more windings per coil than the OEM parts,” Davis says. Doing this allows the coil to more efficiently transfer energy throughout the operating range of the engine.

Bigger Is Better -False

Performance Distributors SOS coils for LS engines and one of its Ford replacement Screamin' Demon coils, both fit into the OEM mounting locations and are similar if not identical to the OEM part size.

This might be an area where consumers, even those with a fundamental understanding of how an ignition coil is constructed could make an improper assumption. More windings and heavier gauge material for those windings typically improves the performance of a coil. Davis points out however that often even with those changes an upgraded coil can fit within an OEM size case or housing, or one that is only slightly larger.

“Stock size casings can often do the trick with the proper windings,” Davis says. “In some instances you may have to go to a bigger mold for the body of the coil, but often that’s not the case.” Davis says the key is to utilize the correct number of windings and the correct gauge (size) material for those windings. Doing so often ensures the coil fits in OEM size packaging, but performs significantly better.


Ballast Resistors Aren’t Needed With Aftermarket Coils -False

This last misconception example is going to exclude modern coil over plug, or coil pack ignition system vehicles, and primarily pertain to the older muscle car crowd, some of you reading this may have no idea what a ballast resistor is.

A ballast resistor restricts current flow in an electrical circuit. In an ignition system equipped with a ballast resistor, the ballast resistor restricts current flow to the coil. It’s not unheard of for enthusiasts upgrading to an aftermarket coil, or making ignition system repairs to discard the ballast resistor or to disregard replacing it.

Davis’s advice is to follow the coil manufacturer’s instructions regarding ballast resistor use with a replacement coil. “Go by the coil manufacturer’s instructions on whether or not to run a resistor. If the coil requires a resistor -and your prior coil did not you may very well burn out your new coil in a short period of time. And conversely, if your new coil manufacturer does not want you to run a ballast resistor -and you did with your prior coil, you may not receive the performance benefit of your new coil.”

Performance Distributors manufactures a wide array of ignition products for many modern and classic vehicles, including trucks and muscle cars. Its web-site is also packed with helpful information for upgrading and even troubleshooting ignition systems. Be sure to check them out for your next ignition upgrade project.