How ACCEL's Ceramic Boots Can Cure Spark Plug Wire Woes

10 min read

How ACCEL's Ceramic Boots Can Cure Spark Plug Wire Woes

10 min read

In a world of ported cylinder heads, positive displacement superchargers, and mutli-stage nitrous kits, spark plug wires don’t tend to get the level of attention that they really should. Although they aren’t headline-grabbing horsepower mods like the aforementioned hardware, spark plug wires do play an integral role in the proceedings – after all, without proper spark, you’re not going to get proper combustion. While that’s a pretty straightforward proposition under factory-stock circumstances, the story can quickly start to change when your combination ventures into uncharted territory.

“Exhaust heat tends to take a toll on spark plug boots,” explains Accel’s Graham Fordyce. “That damage can happen gradually over time, but with high performance applications, it tends to set in fairly quickly. It often comes down to a lack of adequate clearance between the header tube and the boot – a silicon boot just won’t last if it’s too close to the exhaust.”

Silicon plug boots are available with a range of temperature ratings, but with 600 degrees Fahrenheit being ostensibly a best-case-scenario ceiling for the material’s heat tolerance, silicon boots just can’t keep up with the four-digit temperatures that the surfaces of headers and exhaust manifolds can see. And when the boot starts to give out, ignition system problems are a near-certainty, with issues like rough idle and hesitation when accelerating serving as early symptoms that can foreshadow more trouble as a misfire condition starts to set in.

Accel ceramic spark plug boot, next to a burned conventional boot.

Clearance issues often start to pop up when exhaust modifications enter the mix. If a plug wire boot isn’t up to the task, the heat from a header tube can cause damage to the boot in a surprisingly short amount of time in a high performance application, and that spells trouble for your ignition system.

To prevent such headaches, you need a material that can stand up to that kind of abuse, and that’s why Accel’s Extreme 9000 Series ceramic boot spark plug wires exist. Here we’ll take a closer at how these purpose-built plug wires are designed to help to keep your ignition system running at its best.

Built For Performance

As the name implies, the Extreme 9000 Series ceramic boot spark plug wires ditch the traditional silicon boot in favor of one made from ceramic, a material that’s far more resistant to thermal damage, which in turn yields a thermal rating of up to 2000 degrees for these plug boots.

Even dedicated race cars won’t surpass those kinds of temperatures, which is one of the reasons they’re particularly popular in motorsport applications. “These make sense anywhere you have a lot of under-hood temperature, any situation where clearance is limited between the boot and the exhaust, and any kind of motorsport where you’re using a lot of front brake,” Fordyce says. “So these make a lot of sense in disciplines like circle track and road racing, where the heat generated by the brake system adds to the temperature under the hood.”

Exposed engine bay of a twin-turbocharged drag racing door car.

The significant amounts of heat created during racing events can noticeably elevate under-hood temperatures. Everything from the exhaust to hot front brakes can influence the conditions your spark plug wires will endure.

But he’s also quick to point out that warmed-over road cars can benefit from ceramic plug boots as well.

“If, for instance, you’ve changed camshafts and the new one’s duration is slightly retarded, that will generate a bunch more exhaust heat. And if your cylinder heads are ported and your headers are a larger diameter to match it, that’s going to limit the clearance you have around a spark plug, too. The other thing that folks often don’t realize with street cars is that when you go out cruising, where you’re at low speeds for extended amount of time, there’s not a lot of air moving through the engine compartment. If you don’t have engine fans on and things like that, you can end up with a lot of under-hood heat very quickly.”

The construction of the Extreme 9000 Series wire from the outside inward consists of a 600-degree-rated silicon jacket (which can be bumped up to about 1000 degrees with an insulating sleeve), a fiberglass braid layer for additional strength, a copper-nickel alloy conductor with a graphite coating to aid with conductivity, a ferrite compound designed to reduce radio frequency and electro-magnetic interference, and a Kevlar inner core. “We use a stainless steel terminal with a spring clamp.” Fordyce notes. “And we also use a large band on the crimp to provide plenty of holding strength on the wire itself.”

Cutaway shot of an Extreme 9000 plug wire.

The Extreme 9000 Series spark plug wires provide 500 ohms of resistance per foot of wire to ensure interference-free operation.

Tailored To The Application

When Accel originally debuted the Extreme 9000 Series ceramic boot spark plug wires, there was a clear intent to make an impression, Fordyce tells us. “When we introduced these, the first ones were black wires with a white boot. We did that so the ceramic boot would stand out a bit – the difference would be obvious.” But Accel also realized that wasn’t necessarily to everyone’s aesthetic tastes, so they recently added a black ceramic boot option for those looking for something a bit more visually low-profile.

Both the white and black plug boots can be had in straight, 90-degree, and 135-degree angle configurations, and direct-fit sets are available for a number of popular platforms like Fox-body Mustangs, big and small-block Chrysler engines, and LS applications, among many others.

“We also have three different universal sets for straight, 90-degree, and 135-degree boot angles,” Fordyce points out. “With those the spark plug end is assembled and the builder would route the wires as they see fit, cut and strip the end of the wire, and assemble the distributor end to fit their particular application.”

That ensures that no matter what engine is being worked on, there’s a set of Extreme 9000 Series ceramic boot spark plug wires that will suit the project. “You can buy these individually, too,” Fordyce adds. “So if you’ve just finished your motor and you find one cylinder that keeps burning a boot, you can get one ceramic boot wire to resolve that.”

It’s a convenient option that’ll quickly get you rolling again with issue addressed. And when it comes time to replace all the wires again, you can just score a full set of these and never have to worry about frying spark plug boots again.


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