Building a project car is a long road paved with research, endless parts catalogs, and a healthy dose of frustration when things don’t fit quite right. One of the most overlooked hurdles is finding spark plug wires that actually keep up with your engine’s needs.
In this guide, we’ll break down some spark plug wire lingo, talk about how spark plug wires work, and discuss why choosing a high-quality set is one of the smartest investments you can make for your hot rod or race car.
Spark Plug Terminology
Spark plug wires may seem simple, but the complexity lies below the surface, and some of the terms used to explain how it all works aren’t familiar to everyone. Here's a quick overview of the jargon:
- Resistance (Ohms): A measure of how much a material holds back electricity. Lower is usually better for performance.
- EMI: Electromagnetic Interference. Electronic noise or static caused by electricity. It can mess up radios and engine computers.
- RFI: Radio Frequency Interference. A specific type of EMI that affects radio signals.
- Arcing: When electricity jumps out of the wire and hits the engine block instead of the spark plug.
- EMC: Electromagnetic Compatibility. The ability of different electronic parts to work near each other without causing interference.
- EFI: Electronic Fuel Injection. This fuel delivery system is the brain of most modern engines and is very sensitive to electronic noise.
What Is A Spark Plug Wire?
Think of a spark plug wire as a high-speed electricity delivery conduit. Its only job is to carry a massive bolt of electricity from the ignition coil to the spark plug.
Most standard spark plug wires share a similar sandwich design:
- The Core: The center path where electricity flows.
- Suppression Layer: Insulation that helps keep the electricity on track.
- Fiberglass Braid: A middle layer for strength.
- Silicone Jacket: The outer skin that protects the internals from heat and prevents the electricity from arcing (leaking out and sparking against the engine block).
The Anatomy of a Scott Performance Spark Plug Wire
- Fiberglass/Aramid (Kevlar®) Blend Ferrite Coated Core
- Stranded Alloy – TPI (Turns P/Inch) Determined by Wire design
- Silicone Inner Core for Strength, EMI/RFI Control and Break-down Voltage
- Silicone Outer Core for Abrasion and Heat Resistance
- Fiberglass Sleeving Rated @ 1000˚F
- Additional Silicone Sleeving on Scott Wires Provides Added Protection Against Heat and Abrasion
- Stainless Steel “Snap-Lock” Tab for Positive Lock to Spark Plug
- Bend Crimp for Ultimate Termination
- High Temp Silicone Boot and Heat Shrinks for Added Protection
Are All Spark Plug Wires The Same?
No, they can differ greatly. The internal core determines how much power reaches your engine and how much noise it creates for your electronics. Sleeve thickness, resistance, and end-forming can all vary as well. Read on to learn more about what makes our wires better!
Solid Core Spark Plug Wires
These were the standard before the 1960s. They use a solid or twisted metal center.
- The Good: They have very low resistance, meaning the electricity flows incredibly easily.
- The Bad: They act like little radio antennas. They create Electromagnetic Interference (EMI), or noise. On a modern car, this noise can mess up your radio, confuse your digital gauges, and even cause your Fuel Injection (EFI) to malfunction.
Carbon Core (Spiral Core) Spark Plug Wires
To fix the noise problem, the industry moved to carbon or spiral cores (refer to #2 in the image above). This is now the standard for most performance applications.
- The Good: Carbon cores use a core wrapped in a wire spiral to suppress that electronic noise. This lets you run a high-output ignition without ruining your radio reception or confusing your engine sensors.
- How We Do It: Most wires we make use a high-end spiral core design. This design ensures a full spark without the electronic static. The material makeup of the spiral-wound component, and the number of turns per inch (tpi) directly correlate to wire quality and performance. We use pure copper and copper alloy conductor, wound at 125 or 200tpi.
Spark Plug Wire Thickness: Does Size Matter?
You’ll see wires sold in different sizes, typically: 7mm, 8mm, 8.8mm, and 10mm.
- Standard Wires: Most factory wires are thin (7mm or 8mm). While they work fine for a grocery getter, they often lack the protection needed for high-performance environments. Interestingly, the internal core is often the same size across all diameters - so a thicker wire doesn't necessarily carry more electricity.
- Scott Performance Wires: If the core is the same, why go thicker? Protection. Thicker wires (like our 8.5mm to 10mm options) offer more insulation. This extra padding protects the wire from extreme engine heat and provides better shielding to keep electronic noise from escaping.
Does The Resistance Of A Spark Plug Wire Matter?
Resistance is a measure of how much a wire 'fights' the electricity flowing through it. We measure this in Ohms.
- Standard Wires: Typical factory (OEM) wires are built for longevity, not speed. They often have high resistance, ranging from 3,500 to 4,000 Ohms per foot.
- Scott Performance Wires: Our wires are designed to keep resistance as low as possible so that more energy actually reaches the spark plug, resulting in a cleaner, stronger combustion.
What Makes Scott Performance Spark Plug Wires Different, and Better?
With decades of experience in NASCAR and NHRA, we’ve learned what it takes to survive in brutal racing environments, resulting in products that stand up to the toughest conditions.
High-Quality Design
While standard wires might melt or crack under pressure, our wires are wrapped in a dual layer of premium silicone sleeving. This allows them to withstand temperatures up to 1,200 degrees Fahrenheit.
Industry-Leading Snap Lock Technology
Ever pushed a spark plug boot on and wondered if it actually clicked? Standard wires often use cheap clips that feel mushy. Our wires feature stainless steel snap lock tabs. You’ll feel a definitive click during installation, ensuring a vibration-proof connection.
Custom Fit for Any Application
You aren't limited to generic kits that are always too long or too short. We offer:
- Custom lengths tailored to your engine bay.
- Specific boot angles (straight, 45°, or 90°) to clear headers.*
- A variety of colors to match your build.
*Boot angles are determined by the clearance between your spark plug and surrounding components like exhaust manifolds or headers. Custom boot angles mean the wire can be connected securely without making direct contact with hot surfaces or being forced into a sharp bend.
USA-Based, Industry-Leading Quality Control
Every wire we make is individually continuity and resistance tested on site by our team, right here in the USA. You can be certain the product you receive will do the job well.
About High-Output Ignition Boxes
High-output ignition boxes are not a problem for Scott Performance Wires. Our wires are designed to handle the high voltage and current delivered by aftermarket ignition systems like MSD, Crane, or Mallory. The low-resistance core ensures that the maximum amount of energy still reaches the spark plug.
How Spark Plug Wires Impact Horsepower
Will upgrading your spark plug wires increase horsepower? Indirectly, yes.
While spark plug wires do not create horsepower, they both:
- Prevent the loss of power caused by weak or inconsistent spark.
- Improve the timing of the combustion spark.
A perfectly timed and full-strength electrical impulse will improve combustion efficiency, as it helps the spark plugs do their job. If your current spark plug wires are limiting performance, a new set will unlock more power as well as improved throttle response and engine efficiency.
How Much Heat Can a Spark Plug Wire Handle?
Scott Performance standard wires are rated for temperatures up to 600 °F. For extreme applications, we offer additional woven fiberglass heat sleeving that can withstand even higher temperatures, up to 1200 °F. High heat resistance is important when wires run adjacent to exhaust headers.
Can I Install Spark Plug Wires Myself?
Yes, but keep in mind that if you purchase a Universal or Fit-Your-Own kit, you will need a high-quality wire crimping tool to attach the terminals to the wires. However, if you purchase a Ready-to-Install set, no special tools are required; they are pre-crimped and ready to snap onto your plugs and distributor/coil.
Choose Scott Performance Spark Plug Wires For Your Vehicle
Since 1990 we've been a front runner in the automotive industry, specializing in top-quality spark plug wires that meet the precise needs of engine builders and automotive enthusiasts alike.
We offer both vehicle-specific sets and universal kits that can be tailored to your exact needs. Our spark plug wires are offered in two distinct categories:
| High Performance Low Ohm - Optimized for power and made for racing. | Street Performance - Optimized for everyday performance and a massive upgrade over stock. |
| • 30 Ohm resistance rating* • Hi-Inductance for racing and high performance applications • .090" diameter core for strength and low impedance • .004" pure copper conductor with our proprietary 200 turns per inch winding |
• 300 Ohm resistance rating* • 9MM diameter woven fiberglass sleeve is standard • Heat resistant to 1200°F • Good balance between inductance and reduced noise/RF interference • .065" diameter core • .006" copper alloy conductor with proprietary 125 turns per inch winding |
*Resistance ratings can vary as much as 10 ohms; we match sets to ensure consistency.
Additionally, you can configure our wires with a 10MM diameter wire silicone coated woven fiberglass sleeve, a 9MM woven fiberglass sleeve, or no sleeve. Our woven fiberglass sleeved wires are heat resistant to 1200°F!
| MAKE | SLEEVE TYPE |
| • Ford • Chevy • Dodge • Marine |
• Fiberglass • Silicone • Non-Sleeved |
You can also find some helpful spark plug wire info, including Cap and Coil Type Identification, LS Wire Tips, and how to order Custom Wire Sets, on our blog.
If you want your engine to run at its peak and your electronics to stay quiet, upgrading to a set of 100% American-made Scott Performance wires is the perfect route to ensure peak reliability and power. Get in touch with us today to order yours.