KPMI Black Diamond Exhaust Valve - M8 1.284 OS Inconnel — Harley-Davidson Road King, Road King Special, Electra Glide Ultra Classic (2017-2019)

KPMI Black Diamond exhaust valve for Harley Milwaukee-Eight (M8) engines, oversized 1.284 in. with Inconel construction and proprietary Black Diamond surface hardening. One-piece forging delivers superior wear resistance, reduced friction, and corrosion protection compared to plated alternatives.

Features

• Black Diamond® surface hardening to .002 in depth
• Inconel construction for high-temperature durability
• One-piece forging design
• Optimized flow profile
• Light weight at 0.2 lbs

Specifications

• Brand: KPMI
• Manufacturer Part #: 20-21018K
• Material: Inconel
• Valve Size: 1.284 in oversized
• Length: 3.5 in
• Width: 7.12 in
• Height: 1.5 in
• Weight: 0.2 lbs

Frequently Asked Questions

What is the Black Diamond process?

German proprietary hardening that impregnates stainless steel to .002 in depth, improving wear resistance and corrosion protection over chrome or nickel plating.

Will these fit my M8 engine as-is, or do I need porting?

Verify your M8 cylinder head is set up for 1.284 in oversized valves. Stock M8 heads may require machine work to accept these.

Are these valves used for intake or exhaust?

This is an exhaust valve. Intake valves require a separate part number.

What makes Inconel better than stainless steel?

Inconel handles higher temperatures and retains strength better in exhaust applications, making it ideal for high-performance M8 engines.