M8 +4MM OVERSIZED (Gen. 1)

The ultimate porting package for riders demanding serious race-level performance. Precision 5-axis work, +4mm valves, and a reshaped CNC chamber deliver up to a +24.27% increase in intake airflow and a +44.4% increase in exhaust flow.

A car engine cylinder head showing intake ports and valve seats, with a black gasket around it, set against a black background.

Our M8 +4MM Full Race CNC Porting service is engineered for professional racers and performance enthusiasts who demand serious power from their engines. Leveraging advanced 5-axis CNC technology, this service provides precision-engineered, high-flow ports that unlock your engine’s full potential. The result is one of the most powerful upgrades available, delivering a 24.27% increase in intake airflow and a staggering 44.4% increase in exhaust flow for unmatched power gains and throttle response.

This package is built around massive +4MM oversized stainless steel valves and durable bronze seats, with optional titanium valves available for those seeking the lightest setup for maximum RPM. It also features a fully reshaped CNC combustion chamber for optimized combustion efficiency, a 70mm square intake port modification, and a 2" exhaust flange upgrade to ensure seamless compatibility with other high-performance components.

At Ward Performance, every head undergoes rigorous testing and hand assembly to ensure precise fitment and race-grade reliability. Whether you're chasing records at the track or building the ultimate street machine, our +4MM porting provides a potent, proven upgrade backed by years of expertise in racing and engine development.

Starting at: $3,402.18

    • +4MM Oversized Stainless Steel Valves

      • Engineered for maximum airflow and durability under extreme conditions.

    • +4MM Oversized Titanium Valves (Optional)

      • Ultra-lightweight titanium valves for high RPM performance and reduced valve train mass.

    • Bronze Intake & Exhaust Seats

      • Essential for achieving the +4MM valve size and ensuring long-lasting reliability.

    • Extensive 5-Axis CNC Porting

      • Precision-engineered to optimize intake and exhaust flow for maximum power gains.

    • 70mm Square Intake Port Modification

      • Enhances airflow compatibility with high-performance intake manifolds.

    • 2" Exhaust Flange Modification

      • Ensures optimal exhaust flow to match high-output performance systems.

    • Reshaped CNC Combustion Chamber

      • Optimized for efficient combustion and tailored compression for your build.

    • Multi-Radius Competition Valve Job

      • Delivers smooth airflow through the entire valve lift range for maximum efficiency.

    • Performance Spring Kits (Optional)

      • Choose from Steel .640" High-Performance Springs or Ultra-Light Titanium .640" Springs for precise valve control.

    • Re-Machining of Head Gasket Surface

      • Ensures a perfect seal for peak performance and longevity.

    • Professional Assembly & Testing

      • Each head is thoroughly inspected, assembled, and tested to meet race-grade standards.

    • Typically, this service requires you to send in your existing cylinder heads for modification.

    • For those looking for a quicker option, we offer off-the-shelf core heads that are fully prepared and ready to ship. If you have specific custom needs, we're more than happy to accommodate—just let us know what you're looking for.

    • Still have questions or need help deciding?

    • No worries! We know performance upgrades can be a big decision, and we're here to help.

    • If you're unsure about anything, don't hesitate to reach out to us or visit our FAQ page for more information. We're just a message away and ready to assist!

Start Your Order For +4MM Head Online
  • Close-up of a mechanical engine part with a gold-colored cylindrical pin inside a silver, circular housing, mounted on a black metallic surface.

    Performance Bronze Valve Guides

    High-performance bronze guides are used for durability and precise valve movement.

  • Close-up of an engine cylinder head with two brass valves and threaded holes.

    Multi-radius Competition Valve Job

    Ensures a smooth transition from the valve seat to the inner port, maximizing airflow and enhancing performance.

  • Close-up of a small internal engine component with two silver coil springs and a black metal frame.

    High-lift spring kits (.640" lift)

    Available in steel or titanium, engineered for optimal valve control in high-performance applications.

  • Close-up of an engine cylinder head with visible valve seats and part of the cylinder bore.

    Re-machining of head gasket surface

    Ensures perfect sealing and compatibility with your engine setup.

Close-up of a car engine cylinder head with visible intake and exhaust ports
Close-up of a metallic engine cylinder head with gold-colored circular valves and threaded holes, set on a black surface.
Close-up of a metallic mechanical component with a hollow cylindrical shape, containing brass-colored pins inside.
Close-up of a metallic engine component with two circular chambers and a brass pin inside a black and silver casing.
Close-up of a black and silver motorcycle engine cylinder head with visible intake and exhaust ports.
A sectioned automotive cylinder head with four combustion chambers, metallic surfaces, and black cooling passageways.
Close-up of a KPM piston assembly mounted in an engine cylinder head, with visible head bolts and machined surfaces.
A close-up view of a motorcycle cylinder head with visible intake and exhaust ports.
A detailed view of a motorcycle engine cylinder head with springs and valves.
A close-up view of a car engine cylinder head with valve springs and retaining parts, isolated on a white background.
Automotive engine cylinder head with black cast iron and silver machined metal components.