MSD 31803 Super Conductor Spark Plug Wire Set Big Block Chevy HEI - 8.5mm Black

The MSD 31803 is a vehicle-specific 8.5mm Super Conductor spark plug wire set in black, custom-fit for Big Block Chevy and GMC truck applications equipped with factory HEI ignition (internal or external coil) on 366 and 454 (7.4L) engines from 1988 onward.

MSD's Super Conductor wire is engineered from the inside out to deliver the best of both worlds: ultra-low resistance and superior EMI suppression. With only 40–50 ohms of resistance per foot, it is among the lowest-resistance helically wound wires available. Each foot of finished wire contains over 40 feet of tightly wound copper alloy conductor wrapped around a ferro-magnetic impregnated center core.

Key Features:

• Ultra-low resistance: Only 40–50 ohms per foot — the lowest of any helically wound wire — for maximum spark energy delivery to the plug
• EMI suppression: Ferro-magnetic impregnated center core creates an effective EMI choke, keeping electromagnetic interference inside the wire and away from vehicle electronics
• 8.5mm silicone/synthetic jacket: A proprietary blend of silicone and synthetic material over an extra-heavy glass braid provides exceptional resistance to high heat, abrasion, and tearing
• Dual Crimp stainless steel terminals: Two separate crimps — one securing the wire sleeve, a second grasping the conductor — for a reliable, long-lasting connection with snap-lock retention under the high-temperature boots
• Multi-angle spark plug boots: Eight multi-angle boots at the plug end for flexible routing in tight engine bays; gray distributor boots included
• Custom fit: Pre-cut and assembled specifically for Big Block Chevy/GMC truck HEI applications — no cutting or crimping required
• Emissions compliant: Legal for use on emissions-controlled vehicles, non-emissions-controlled vehicles, and racing applications

The MSD 31803 is a direct bolt-on upgrade that ensures maximum ignition performance, improved throttle response, and protection against interference with modern vehicle electronics.