KPMI Black Diamond Exhaust Valve - 1.284 Oversized Inconel - Harley Milwaukee-Eight
About KPMI
Kibblewhite Precision Machining supplies valves, valve springs, guides and complete top-end kits used by professional V-twin engine builders. Its black diamond valves and spring kits are a standard specification on high-lift cam builds.
The KPMI Black Diamond exhaust valve is an oversized 1.284 inch Inconel valve designed for Harley-Davidson Milwaukee-Eight (M8) engines. Featuring KPMI's proprietary Black Diamond surface hardening, this one-piece forged valve offers exceptional durability and heat resistance for high-performance applications.
Why riders pick this
- Inconel construction for extreme temperature resistance
- Black Diamond surface hardening for superior wear resistance
- One-piece forging for enhanced durability
- Oversized 1.284 inch diameter for optimal exhaust flow
When you're pushing your Milwaukee-Eight engine, the exhaust valves endure extreme temperatures and pressures. This KPMI Black Diamond valve is constructed from Inconel, a superalloy known for its high-temperature strength, and further enhanced with a deep surface hardening process. This combination ensures superior wear resistance and reduced friction, outperforming standard plated alternatives.
Built for Extreme M8 Conditions
- Inconel construction provides high-temperature durability and strength
- Black Diamond surface hardening penetrates deep for superior wear and corrosion resistance
- One-piece forging design ensures maximum structural integrity
- Oversized 1.284 inch diameter for enhanced exhaust flow in performance applications
Unleash Your Milwaukee-Eight's Potential
This exhaust valve is a crucial upgrade for any high-performance Milwaukee-Eight build, especially those involving increased compression, forced induction, or aggressive cam profiles. Its robust construction and advanced hardening process are designed to withstand the most demanding conditions, ensuring reliable performance and extended valve train life. Always verify that your cylinder heads are prepared to accept oversized valves before installation.
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
Common questions
What is the Black Diamond process?
The Black Diamond process is a proprietary German hardening treatment that impregnates stainless steel to a depth of .002 inches, significantly improving wear resistance and corrosion protection compared to traditional chrome or nickel plating.
Will these oversized valves fit my M8 engine without modifications?
These are 1.284 inch oversized exhaust valves. Stock Milwaukee-Eight cylinder heads may require machine work, such as porting or new valve seats, to properly accept these larger valves. Confirm with your engine builder.
Are these valves used for intake or exhaust?
These KPMI Black Diamond valves are specifically designed and engineered for exhaust applications in Milwaukee-Eight engines.
Ordering from Vtwinbikers
- Brand new, sourced through authorized US distribution — never used, never grey-market.
- Not sure it fits? Use Shop by Bike to filter by your year and model, or email us and we will confirm before you order.
- Harley-Davidson and Indian Motorcycle is all we do, so you are talking to people who ride what you ride.
| BRAND | KPMI |
| TYPE | Engine |
| SKU | 191-17045 |
| WEIGHT | 0.2 lb |
