5150 AutoSport B48 Billet Main Caps

As B48 builds continue to push beyond 900+ WHP, we've seen the limitations of the factory main caps under extreme cylinder pressure and crankshaft loads. Even the slightest main cap movement can affect main bearing alignment, oil clearance, and ultimately the reliability of your engine.

Our CNC-machined billet steel main caps are heat treated for maximum strength and feature a dowel-pinned design that positively locates each cap, virtually eliminating cap movement under extreme horsepower and high-RPM operation.

Benefits of 5150 AutoSport Billet Main Caps

• CNC-machined from high-strength billet steel
• Heat treated for maximum durability and strength
• Dowel-pinned design for precise cap location and reduced cap walk
• Increased rigidity over OEM cast main caps
• Reduced main cap flex under extreme cylinder pressure
• Improved crankshaft stability at high RPM and boost
• More consistent main bearing bore geometry
• Better oil clearance control for increased bearing life
• A stronger foundation for high-performance and race-built B48 engines

When you're building a 900+ WHP B48, every thousandth of an inch matters. Our billet, heat-treated, dowel-pinned main caps keep the crankshaft securely located, providing the bottom-end stability required to withstand extreme boost, high RPM, and the abuse of competitive motorsports.

Important: Billet main caps are not a simple bolt-on upgrade. The engine block and main caps must be precision machined, followed by align boring and align honing, to restore perfect main bearing geometry and ensure proper bearing clearances.

Built for racers. Proven through real-world testing. Engineered by 5150 AutoSport for the next generation of high-horsepower B48 engine builds.

For a detailed look at the engineering, testing, and benefits of our Billet Main Caps, read our full technical article.

https://5150autosport.com/blogs/product-faq/b58-s58-billet-main-caps-cap-walk