5150 AutoSport

N55 Cylinder Head Service by 5150 AutoSport

$1,400.00 USD

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Service Stage 1 Stage 2 Pro-Xtreme

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5150 AutoSport Performance Cylinder Head Services for BMW N55 Engines

Please note that price is based on customer providing core. If you need help sourcing a core, please contact our sales team.

Investing in a performance cylinder head service is crucial for optimizing engine potential in performance builds. We offer three levels of service to meet your budget and build goals, from OEM refresh to full race-level machining:

Stage 1 – OEM Refresh (Rebuild & Reliability Focused)

Ideal for stock or mildly modified engines needing a proper refresh.

The cylinder head is fully disassembled, cleaned, and soda blasted to remove carbon and contaminants. Valve guides are measured and inspected, with new guides installed if needed, then precision reamed and honed for proper clearance. A 5-angle valve job is performed to restore sealing efficiency, followed by resurfacing to ensure a flat, true mating surface. New Viton valve seals are installed, the head is fully reassembled using OEM valves, guides, springs, and retainers, and pressure tested after assembly.
Optional service upgrade: add a high-performance valve spring kit.

Stage 1 at a Glance:

Disassemble and Clean
Soda Blast
Inspect and Measure Valve Guides
- Removal and Installation of new Guides, if necessary
Ream and Hone Valve Guides
5-Angle Valve Job
Resurfacing
Final Wash
Install New Viton Valve Seals
Setting of Seat Pressure
Full Reassembly
Pressure Testing after assembly

Stage 2 – Performance Valvetrain Upgrade

For higher RPM builds and increased durability.

Includes everything from Stage 1, plus upgraded high-performance valves, a high-performance valve spring kit, and new valve locks/keepers. This stage improves valvetrain stability, reduces the risk of valve float, and prepares the head for more aggressive use while retaining OEM-style machining processes.

Stage 2 at a Glance:

Disassemble and Clean
Soda Blast
Removal of OEM Valve Guides
Installation of Performance Valve Guides
Ream and Hone Valve Guides
5-Angle Valve Job
Resurfacing
Final Wash
Install New Viton Valve Seals
Install New High Performance Valve Spring Kit
Install New High Performance Valve Kit
Install New High Performance Valve Keepers
Setting of Seat Pressure
Full Reassembly
Pressure Testing after assembly

Pro-Xtreme – All-Out Performance Cylinder Head Service

Designed for high-horsepower, forced-induction, and competition builds.

The cylinder head undergoes complete disassembly, cleaning, and in-depth inspection, including crack, leak, and pressure testing. Factory valve guides are replaced with high-performance guides, then precision reamed and honed for extreme heat and RPM stability.

CNC multi-angle porting is performed on both intake and exhaust ports to improve airflow consistency across all cylinders. A CNC multi-angle intake valve job and radius exhaust valve job optimize flow into and out of the combustion chamber. Valves are unshrouded to further enhance airflow, and preventative chamfering is applied in critical areas to reduce stress concentrations.

The mating surface is trueness checked, resurfaced, and verified again for perfect sealing. After machining, the head is thoroughly washed and assembled using balanced and blueprint-matched high-performance valves, along with balanced valve springs and retainers for precise valve control and long-term durability.

Pro-Xtreme at a Glance: