MTG Dynamics B58/S58 Billet Main Caps
When building a high-horsepower BMW B58 engine, the strength of the bottom end becomes just as important as the rotating assembly itself. As cylinder pressure, boost, and RPM increase, the factory cast main caps can begin to flex under extreme loads. Even minimal cap movement can affect main bearing alignment, bearing clearances, and crankshaft stability.
The MTG Dynamics B58/S58 Billet Main Caps are CNC-machined from premium billet steel to provide substantially greater rigidity than the factory main caps. Designed for serious engine builders, these caps help maintain precise main bore geometry, reduce cap walk, and provide the stable crankshaft support required for extreme horsepower applications.
Whether you're building a 900 HP street car or a 1,500+ HP drag or roll racing engine, billet main caps provide one of the strongest foundations for a reliable B58 engine.
Features
CNC-machined from high-strength billet steel
Direct replacement for factory B58/s58 main caps (professional machining required)
Significantly stronger than OEM cast main caps
Helps reduce main cap walk under extreme cylinder pressure
Improves crankshaft stability at high RPM
Maintains consistent main bearing geometry
Promotes improved bearing life and oil clearance consistency
Designed for high-boost and high-horsepower engine builds
Manufactured in the Turkiye
Benefits
Stronger bottom-end foundation
Reduced main cap flex
Improved bearing reliability
Better crankshaft support
Increased durability for extreme horsepower applications
Ideal for race, drag, roll racing, and high-performance street builds
Installation Notes
Professional engine machining is required.
These billet main caps are not a bolt-on upgrade. Installation requires:
Line boring
Align honing
Verification of main bearing housing bore dimensions
Proper main bearing clearance measurement during engine assembly
Failure to perform these machining operations may result in premature bearing failure or engine damage.
Recommended Applications
800+ HP Street Builds
Big Turbo B58 Builds
Drag Racing
Roll Racing
Standing Mile Competition
Road Racing
Dedicated Competition Engines
Engine Fitment
Fits BMW B58 Gen 1 and Gen 2 engines, including:
BMW M140i
BMW M240i
BMW 340i
BMW 440i
BMW 540i
BMW 640i GT
BMW 740i
BMW X3 M40i
BMW X4 M40i
BMW X5 xDrive40i
BMW X6 xDrive40i
BMW X7 xDrive40i
BMW Z4 M40i
Toyota GR Supra (A90/A91)
