BMW Machine Shop Services
Precision BMW machining for customer-supplied engine blocks and cylinder heads — performed entirely in-house at VAC Motorsports for strength, sealing, and repeatable performance.
Precision BMW Machining — Performed In-House
VAC Motorsports provides a complete range of stand-alone machine shop services for BMW engine blocks and cylinder heads. Each operation is performed using dedicated fixtures, CNC equipment, and application-specific processes developed through decades of BMW performance engine work.
Our Core Machine Shop Services
Block Sleeving
Restore or reinforce cylinder wall integrity for damaged or high-power applications. Designed for stable ring seal and long-term durability.
Closed Deck Conversion
Reinforce open-deck BMW blocks for high-boost and high-cylinder-pressure environments while maintaining proper coolant flow.
Combustion Chamber CNC Modification
Precision chamber unshrouding and profiling to improve mid-lift airflow and combustion efficiency.
Performance Cylinder Head Services
Three staged options to match your goals — from performance reconditioning to full CNC port development and race-ready valvetrain upgrades.
5-Axis CNC Porting
Available as a stand-alone airflow upgrade for customer-supplied cylinder heads.
Cylinder Head Repair & Reconditioning
Pressure testing, resurfacing, valve service, guide replacement, and full inspection to restore proper operation and sealing.
Customer-Supplied Core Required
All machine shop services are performed on customer-supplied engine components. If you do not have a usable core, contact our team for sourcing options.
Sales@VACMotorsports.comReady to Start Your Machining Project?
Email us your engine type, power goals, and required service — our team will guide the correct machining path for your build.
Contact SalesBlock Sleeving Service
Modern BMW aluminum engine blocks are incredibly efficient — but under extreme cylinder pressure and high boost, factory cylinder wall thickness can become a limiting factor. Block sleeving replaces the original cylinder surface with a precision-machined, high-strength liner designed to maintain bore geometry, improve ring seal, and support significantly higher power levels.
When Should You Sleeve Your Engine?
This short video explains the real-world scenarios where sleeving becomes the correct solution for durability, power goals, and long-term reliability.
Why Builders Choose to Sleeve a Block
High-strength ductile iron sleeves reinforce thin OEM cylinder walls and help reduce distortion under extreme boost and cylinder pressure.
Maintaining round, true cylinders under heat and load improves compression consistency and oil control at high RPM.
A stronger cylinder foundation supports increased boost, higher cylinder pressure, and more aggressive engine combinations.
Wear-resistant cylinder surfaces reduce scuffing, extend ring life, and improve long-term reliability in high-stress builds.
High-quality sleeve materials and proper installation promote consistent thermal behavior under sustained load.
Sleeving provides a path to save damaged or worn cylinders and return the block to a usable, high-performance foundation.
What We Need From You
Supply your bare engine block along with the main bearing caps. VAC performs all machining operations in-house using dedicated BMW-specific processes.
Sales@VACMotorsports.comThis Is Not a General Machine Shop Operation
Cylinder sleeving requires precise machining, correct material selection, and strict control of bore geometry. When executed incorrectly, distortion and sealing issues occur. VAC performs this work in-house using processes developed specifically for BMW performance engines.
Ready to Build a Stronger Foundation?
Email your engine type, power goals, and photos of your block to get started.
Email Sales@VACMotorsports.comClosed Deck Conversion
For open-deck BMW engine blocks, a closed deck conversion reinforces the upper cylinder area to help reduce cylinder movement under extreme boost and cylinder pressure. The goal is improved deck support, more consistent head sealing, and a stronger foundation for high-horsepower builds.
- N54
- N55
A quick visual breakdown of why open-deck blocks benefit from additional deck support in high-boost builds.
What a Closed Deck Conversion Helps Solve
Open-deck architecture leaves the upper cylinder area less supported. Under extreme cylinder pressure, this can allow cylinder movement and deck instability that may contribute to head sealing challenges. A closed deck conversion reinforces the deck around the cylinders to improve support where it matters most.
Key Benefits of a Closed Deck Conversion
Improved Deck Support
Reinforces the deck around the cylinder tops to help reduce movement under high boost and extreme cylinder pressure.
Head Gasket Sealing Stability
A more supported deck can help reduce sealing variability in aggressive build environments.
High-Boost Readiness
Designed for builds where cylinder pressure exceeds what the factory open-deck structure is intended to handle.
Coolant Flow Considered
Reinforcement is designed to maintain cooling function while adding critical deck support.
What’s Included in VAC’s Closed Deck Conversion
- CNC-machined deck inserts designed to reinforce the open-deck void around the cylinders
- Precision coolant passage design to support cooling function while increasing deck rigidity
- Deck preparation and machining operations required for proper insert fitment
- CNC deck-plate boring & honing to support round, true cylinders under simulated clamping conditions
Important: Pricing includes the closed deck conversion service only. Core engine block and short block assembly are not included.
Combustion Chamber Modification Service
VAC’s Combustion Chamber Modification service is a precision CNC machining process designed to unlock additional airflow where it matters most: mid-lift. By carefully unshrouding the chamber area adjacent to the valves, airflow can improve from initial lift through max lift, supporting stronger cylinder filling, cleaner burn characteristics, and improved performance potential.
What Is a Combustion Chamber Modification?
In many BMW cylinder heads, the combustion chamber walls can partially “shroud” the valves as they open — especially at mid-lift. This reduces the effective airflow path during the portion of valve movement where the engine spends a significant amount of time. VAC’s CNC chamber modification precisely reshapes targeted areas of the chamber to reduce shrouding and improve airflow efficiency, while maintaining a controlled, repeatable result.
Key Benefits
More Mid-Lift Flow
Improved airflow where the valves spend much of their time — supporting better cylinder filling and stronger efficiency.
Improved Burn Characteristics
A cleaner, less restricted path around the valve can support a more efficient mixture motion and combustion process.
Supports Power Goals
Better chamber/valve relationship can support performance gains when paired with proper valve work, porting, and calibration.
Repeatable CNC Accuracy
CNC machining provides a consistent result compared to hand-blending alone — critical when matching chambers across cylinders.
When You Should Consider This Service
- You want improved airflow efficiency without jumping straight to a full port program
- Your head is already being serviced and you want to maximize the value of the job
- You are building a higher-output street/track engine where mid-lift flow matters
- You want a repeatable, measured approach rather than “hand-only” guesswork
What We Need From You
A customer-supplied cylinder head core is required. For fastest quoting, include your engine code, intended use (street/track/drag), and your performance goals. If you do not have a core, email our team to discuss sourcing options.
All VAC cylinder head services are performed on existing customer cores. This requires the customer's core to be supplied to VAC for servicing.
Why Chamber Work Needs Precision
Combustion chamber geometry impacts flow, compression behavior, and chamber-to-chamber consistency. VAC uses a controlled CNC process to improve valve unshrouding while maintaining a repeatable result across cylinders. This is how you build performance without sacrificing consistency.
Performance Cylinder Head Service
VAC Motorsports Performance Cylinder Heads are built from customer-supplied cores using precision machining, proven airflow development, and valvetrain upgrades designed for real performance. From stock-class rebuilds to full race programs, each stage is engineered to support your power goals with repeatable results.
All VAC cylinder head services are performed on existing customer cores. This requires the customer's core to be supplied to VAC for servicing.
Available Performance Stages
Stage 1 – Performance Reconditioning
A stock-class legal upgrade that improves sealing, airflow efficiency, and durability while maintaining factory drivability.
- Multi-angle valve job (Serdi)
- New valve guides & seals
- Valve reconditioning & blueprinting
- Resurfaced mating surface
- Valve unshrouding
Stage 2 – High Performance Street / Track
Enhanced torque band and stronger mid-to-top end power with upgraded valvetrain stability.
- Max-performance valve job
- VAC performance valve springs
- Performance retainers
- Valve unshrouding & chamber work
Stage 3 – Maximum Performance
The ultimate cylinder head package with full CNC port development and race-proven airflow.
- 5-Axis CNC porting
- Stainless performance valves
- VAC high-performance springs
- Titanium or steel retainers
- Chamber profiling & CC matching
5-Axis CNC Cylinder Head Porting
VAC’s legendary 5-Axis CNC porting process delivers fully developed airflow with unmatched accuracy and repeatability. This is complete port architecture based on proven flow bench and real-world performance data.
Why 5-Axis CNC Porting Matters
True 5-axis machining allows complete access to the intake port, exhaust port, and chamber from the correct angle, producing a mathematically accurate and fully developed port shape that traditional hand porting cannot replicate with the same consistency.
Key Benefits
Identical Port Geometry
Balanced airflow across every cylinder for smoother, more efficient power delivery.
Flow Bench Developed
Port designs are based on real airflow data and decades of BMW race engine development.
Supports High-RPM & High-Boost Builds
Allows the engine to move the air required for maximum performance.
Repeatable Results
The same proven port program can be reproduced for multiple builds.
Available as a Stand-Alone Service
This service is available separately from complete cylinder head packages and does not include disassembly, cleaning, or valvetrain components.
What We Need From You
A customer-supplied cylinder head core is required. Include engine type, intended use, and power goals for the correct CNC port program.
Airflow Is Geometry — Not Just Size
Larger ports alone do not make more power. Proper cross-section, velocity, and short-side control determine real engine performance across the usable RPM range.
Cylinder Head Repair, Exchange & Custom Services
Not every cylinder head needs a full performance program — sometimes it needs to be saved. VAC’s in-house machine shop provides repair, inspection, and custom cylinder head services to bring damaged BMW heads back to spec (or beyond), based on your build goals and the condition of your core.
Common Issues We Diagnose & Repair
Cracked / Leaking Cylinder Heads
Inspection and testing to identify cracks, porosity, or leak paths and determine whether the head can be salvaged.
Dropped Seats / Seat Damage
Evaluation of valve seat integrity, sealing surfaces, and corrective machining strategies when seat failure occurs.
Bent Valves / Valvetrain Failures
Diagnosis of valvetrain damage and corrective service to restore sealing, stability, and reliability.
Warped Mating Surfaces
Resurfacing and trueness verification to support proper head gasket sealing and long-term stability.
Worn Guides / Poor Sealing
Guide wear can destroy sealing and stability. We inspect guide condition and service as needed to restore proper valve control.
Damaged Cores / Unknown History
If the head came from a failed build or unknown source, we assess it properly before any performance work is recommended.
Services Available (Based on Core Condition)
- Complete disassembly, cleaning & inspection
- Leak, crack & pressure testing (as required)
- Valve guide service (labor included; new guides additional as needed)
- Valve seals
- Multi-angle valve job using Serdi equipment
- Valve reconditioning & blueprinting (as applicable)
- Resurface & verify mating surface trueness
- Chamber cleanup / unshrouding (when appropriate)
- Complete reassembly (when quoted as a package)
- Custom valvetrain upgrades (springs, retainers, valves) based on intended RPM / boost / cam profile
Because damage varies widely, repair services are quoted based on your specific core.
Exchange / Replacement Options
If your core is not repairable — or if you don’t have a usable cylinder head — VAC can help guide you on exchange or replacement options depending on current core availability and your engine platform.
A cylinder head core is required for all head work. If you do not have a core, email our team to discuss sourcing options.
Why Proper Diagnosis Matters
Many cylinder head problems look the same from the outside but have very different root causes. Proper testing and measurement is the difference between a repaired head that lasts — and a repeat failure. VAC’s machine shop evaluates the core first, then recommends the correct repair or performance path.