MSD 31339 Super Conductor Spark Plug Wire Set Ford HEI Red - 8.5mm 351M-400

The MSD 31339 Super Conductor Spark Plug Wire Set is a custom-fit, vehicle-specific 8.5mm performance wire set designed for Ford 351M/400 engines equipped with HEI-style distributors. Built around MSD's legendary Super Conductor technology, this set delivers maximum spark energy to each plug while keeping electromagnetic interference fully suppressed.

At the core of every Super Conductor wire is a copper alloy helical winding so tight that over 40 feet of conductor is packed into a single foot of finished wire. The result is an industry-leading resistance of just 40–50 ohms per foot — the lowest of any helically wound wire — while achieving RFI suppression equivalent to a 1,500-ohm wire. A ferro-magnetic impregnated center core creates an effective EMI choke that keeps interference contained inside the wire and away from sensitive vehicle electronics.

Key Features:

• 8.5mm diameter with a proprietary synthetic/silicone outer jacket over an extra-heavy glass braid and dielectric insulator for superior heat and abrasion resistance
• Copper alloy spiral-wound conductor with only 40–50 ohms resistance per foot for maximum spark energy transfer
• Ferro-magnetic impregnated core produces an effective EMI choke, preventing radio frequency interference with onboard electronics
• Dual crimp stainless steel terminals with snap-lock design under high-temperature silicone HEI boots for a secure, rattle-free connection
• Multi-angle spark plug boots for flexible routing in tight engine bays
• Red jacket finish for a clean, high-performance appearance
• Includes clip-on cylinder number markers for easy wire identification during installation
• Custom fit for Ford 351M/400 engines with HEI distributor

Sold as a complete set, the MSD 31339 is a direct bolt-on upgrade that delivers measurable ignition performance gains with zero compromise on EMI suppression — ideal for street, strip, or high-performance builds.