B46 Cylinder Head Service by 5150 AutoSport

Price is based on the customer providing a cylinder head core. If you need help sourcing a core, please contact our sales team.

The BMW B46 engine responds exceptionally well to valvetrain and airflow improvements—and 5150 AutoSport's Pro-Xtreme Cylinder Head Service is designed to extract every ounce of potential. Built for high-performance street, track, and race applications, this service includes precision CNC porting, high-performance valvetrain upgrades, and meticulous machining using state-of-the-art 5-axis equipment.

Whether you're pushing more boost or chasing higher RPM, this service provides the consistent flow, improved sealing, and upgraded durability needed to support power reliably. Every head is fully assembled, pressure-tested, cleaned, and delivered ready for installation by your engine builder.

Service Includes:

Disassembly, Cleaning & Inspection

The head is completely disassembled, pressure tested, and inspected for cracks, warping, or other damage. Carbon buildup and oil residue are thoroughly removed to ensure clean surfaces for machining and porting.

CNC-Installed High-Performance Valve Guides

The factory valve guides are removed and replaced with upgraded high-temperature performance guides, then honed to exact specifications. These provide improved thermal stability and reduced wear under high-RPM, high-load conditions.

5-Axis CNC Porting

Intake and exhaust ports are reshaped and enlarged using our Rottler EM69HP 5-axis CNC for maximum airflow and consistency across all cylinders. Porting reduces turbulence, improves throttle response, and supports higher horsepower at every RPM.

Multi-Angle CNC Valve Job (Intake & Exhaust)

The intake seats receive a multi-angle CNC valve job for optimized air-fuel flow. The exhaust seats are finished with a smooth-radius cut to improve gas evacuation. Both sides are machined to exact tolerances for consistent sealing and flow.

Unshrouding of Valves

Material is removed from the combustion chamber walls near the valve seats to reduce restriction around the open valve. This results in improved airflow and more efficient combustion, especially at higher lift.

Preventative Chamfering

Critical edges are chamfered to reduce stress points and prevent future cracking or damage. This detail adds long-term durability and aids in sealing.

Mating Surface Trueness Check & Resurfacing

The cylinder head mating surface is measured for flatness, resurfaced if needed, and re-checked. A flat surface is critical for proper sealing with the head gasket and reliable combustion under high boost or compression.

Final Cleaning & Assembly

After machining, the head is washed again to remove all metal debris. It is then reassembled with:

• One-Piece High-Performance Valves: Blueprinted and weight-matched for smoother operation and reduced wear.
• Balanced Valve Springs & Retainers: Upgraded to handle higher RPM and prevent valve float. Each component is matched for durability, strength, and precision.

Why This Matters for Your Build

• Supports increased airflow for more power and torque
• Improves combustion chamber efficiency and reliability
• Built with race-proven parts and precision CNC machining
• Ensures consistent performance across all cylinders
• Fully assembled and ready for timing setup by your engine builder