King Engine Bearings MB 509XPC STDX XPC Series pMaxKote Coated Main Bearing Set for Chevrolet 400 V8

The King Engine Bearings MB 509XPC STDX is a premium XPC Series main bearing set engineered for the Chevrolet 400 small block V8. Designed for circle track, drag racing, offshore, and other high-performance racing applications, this set delivers the advanced metallurgical and geometric technologies demanded by serious engine builders.

At the heart of the XPC Series is the pMaxBlack™ tri-metal overlay, a surface-hardened lead-tin-copper formulation electroplated onto a copper alloy substrate. With 5% copper content and a proprietary nano-scaled hardening process, pMaxBlack™ achieves a 29% increase in overlay hardness (18.1 HV) and an overall 24% increase in load capacity — up to 10,200 psi — compared to conventional tri-metal race bearings.

Applied over the pMaxBlack™ layer, King's factory-applied pMaxKote™ nano-composite polymer coating functions as a fourth protective layer. It contains ceramic nano-composite particles that significantly enhance wear resistance, protect against cavitation erosion, and guard bearing surfaces during periods of oil starvation or minimum oil film thickness — all without adding any wall thickness or altering precision oil clearances.

The STDX designation indicates standard bore size with extra oil clearance, making this set ideal for race engine builds requiring slightly increased oil flow to the main bearing journals.

Key Features:

• XPC Series — King's premium race bearing line combining pMaxBlack™ and pMaxKote™ technologies
• pMaxBlack™ Overlay — 5% copper content with nano-scaled hardening; 24% greater load capacity (10,200 psi) over standard tri-metal overlays
• pMaxKote™ Nano-Composite Polymer Coating — Factory-applied fourth layer; enhances wear and seizure resistance with zero added wall thickness
• SecureBond™ Adhesion Process — Micro-etch surface preparation that strengthens tri-metal layer integrity and reduces risk of delamination under extreme loads
• Standard Size / Extra Oil Clearance (STDX) — Optimized for race applications requiring additional oil flow
• Designed for use with steel crankshafts in high-load, high-RPM applications
• Manufactured entirely in-house by King Engine Bearings for consistent tolerances and quality control

King Engine Bearings has specialized exclusively in engine bearings since 1960, supplying race teams and engine builders worldwide. The MB 509XPC STDX is the top-tier main bearing choice for builders extracting maximum performance from the Chevrolet 400 V8 platform.