King Engine Bearings MB5730XP STDX XP-Series Main Bearing Set Standard Size

The King Engine Bearings MB5730XP STDX is a complete XP-Series main bearing set in standard size, engineered for high-performance and racing applications. King Engine Bearings has specialized exclusively in engine bearings since 1960, and the XP-Series represents their pinnacle racing bearing technology — purpose-built for sustained, high-load performance environments including road racing, circle track, and endurance applications.

pMaxBlack™ Tri-Metal Construction:

The XP-Series is built around King's proprietary pMaxBlack™ tri-metal structure, featuring a copper/lead Babbitt overlay, a nickel barrier layer, and a high-strength steel backing. The layers are bonded using King's SecureBond™ adhesion process, delivering superior stability and durability under race conditions. The result is a bearing that is 24% harder than conventional tri-metal race bearings, with 15%–30% greater load capacity compared to standard bearings.

Key Features:

• pMaxBlack™ Tri-Metal Structure — Copper/lead Babbitt layer with nickel barrier over steel backing for exceptional hardness and fatigue resistance
• SecureBond™ Adhesion Process — Superior bonding between overlay and intermediate layers for long-term stability
• Bull's Eye Tolerance™ — Wall thickness tolerances held to ±0.0001 in., the tightest in the industry, with all shells matched
• Enlarged Chamfered Oil Holes — Promote enhanced oiling with full, 3/4, or 1/2 groove configurations for uncompromised lower shell load capacity
• Narrowed Design — Mains are narrowed to accommodate large-radius crankshafts, including aftermarket forged steel units
• Medium Eccentricity — Optimizes load distribution and oil film maintenance across the bearing surface
• 0.0005 in. Hardened Performance Overlay — Metallurgically enhanced overlay withstands greater loads and resists surface fatigue
• Standard Size (STDX) — Direct-fit standard crankshaft sizing for stock-dimension journals

The XP-Series was developed specifically for performance applications using forged steel aftermarket crankshafts that produce high loads for extended periods — making it the ideal upgrade for any serious engine build. Sold as a complete main bearing set.