MSD 31223 8.5mm Super Conductor Universal Spark Plug Wire Set 8-Cylinder 90° Plug/90° Plug

The MSD 31223 is a universal-fit, cut-to-length 8.5mm Super Conductor spark plug wire set for 8-cylinder engines. Designed for use with late-model HEI-style distributor caps — including Ford Duraspark and MSD Cap-A-Dapt systems — this unassembled set gives you the flexibility to route and trim each wire to your exact specifications for a clean, custom installation.

At the core of the Super Conductor's performance is a tightly helically wound copper alloy conductor that delivers only 40–50 ohms of resistance per foot — the lowest of any spiral-wound wire — while simultaneously providing RFI/EMI suppression equivalent to a 1,500-ohm wire. Over 40 feet of conductor is packed into every single foot of finished wire, and the ferro-magnetic impregnated center core creates a highly effective EMI choke that keeps interference contained within the wire and away from sensitive vehicle electronics.

The outer jacket is a proprietary blend of silicone and synthetic materials over an extra-heavy glass braid, providing excellent resistance to high heat, abrasion, and tears. The conductor core also incorporates DuPont Kevlar for added tensile strength. Dual-crimp stainless steel terminals secure both the outer sleeve and the inner conductor independently for a reliable, pull-proof connection under high-demand conditions.

What's Included:

• 8 spark plug wires with 90° boots pre-installed — wire lengths: 2 × 56", 2 × 50", 2 × 42", 2 × 32"
• 1 coil wire — 32"
• Distributor cap boots and terminals (90°)
• Mini-Stripper-Crimper tool for custom length termination

Key Features:

• 8.5mm diameter spiral-core construction
• 40–50 ohms/ft resistance — lowest of any helically wound wire
• Ferro-magnetic impregnated core for effective EMI/RFI suppression
• DuPont Kevlar-reinforced conductor core for tensile strength
• Proprietary silicone/synthetic outer jacket — heat and abrasion resistant
• Dual-crimp stainless steel terminals with snap-lock design
• Silicone 90° spark plug and distributor boots included
• Compatible with late-model HEI-style caps (Ford Duraspark, MSD Cap-A-Dapt)
• Sold as a complete unassembled set — cut to your desired length