RLP Spark Plug Wire Set 8.5mm Red Silicone Jacket with 90° Boots — Universal Fit, 450°F Heat-Resistant

RLP's Universal 8.5mm spark plug wire set is a red silicone-jacketed ignition wire kit with 90° boots designed to upgrade OE systems for improved spark delivery and durability while replacing part number 4041.

This wire set is built for street-driven cars and trucks that need more reliable high-voltage transfer than stock leads provide. Constructed with a high-dielectric EPDM core, a tightly woven fiberglass braid and a high-gloss 450°F silicone jacket, these wires balance heat resistance, pull strength and radio-frequency interference (RFI) suppression. Stainless steel plug terminals and compatibility with both pre- and post-HEI systems make this a versatile option for universal or custom-fit ignition upgrades.

How do these wires improve ignition performance?

These wires are engineered to deliver more usable ignition energy to the spark plug by limiting internal resistance and shielding electrical noise. The conductive core and controlled resistance allow a stronger, longer-lasting spark, which helps combustion stability and throttle response without altering engine tuning.

• 5000 ohms/ft resistance for controlled energy transfer
• Conductive carbon-black core for RFI suppression
• Stainless steel terminals for consistent conductivity
• Tightly woven fiberglass braid increases tensile strength

Will these wires survive high underhood temperatures?

Yes — the double-layer silicone jacket is rated to 450°F and resists heat, oil, and chemicals commonly found in engine bays. The high-gloss silicone also protects the inner insulation from cracking and aging, extending service life in demanding environments.

• 450°F-rated silicone outer jacket for extreme heat tolerance
• EPDM inner insulation for high dielectric strength
• Moisture- and chemical-resistant construction for longevity

Are these wires compatible with my vehicle and installation needs?

RLP designed this set as a universal solution that can be used in both universal and custom-fit applications for early and late model cars and trucks. They fit pre- and post-HEI ignition systems and are offered as a direct replacement for part number 4041, making them suitable for many retrofit and performance projects.

• Universal and custom-fit applications supported
• Replaces OEM part number 4041 for straightforward swapping
• Compatible with pre-HEI and post-HEI ignition systems

How easy is installation and what warranty is included?

Installation is straightforward for anyone familiar with spark plug routing: remove the old leads, match lengths and attach the 90° boots to the plugs and distributor/coil. The stainless steel terminals and robust braid make the wires resilient during repeated handling, and RLP backs the set with a two-year warranty for added confidence.

• 90° plug boots for tight or angled plug wells
• Stainless steel plug terminals for secure connections
• 2-year warranty for defects and workmanship

Who is this for: This RLP 8.5mm red silicone spark plug wire set is aimed at street drivers, hobbyists and mechanics who want a durable, high-heat-resistant replacement that improves ignition delivery without complicated modifications. It's a good pick for restoration projects, performance tune-ups, and anyone replacing worn or noisy stock leads who needs a universal option that replaces part number 4041.