King Engine Bearings MB512XP XP Series Tri-Metal Crankshaft Main Bearing Set

The King Engine Bearings MB512XP is a high-performance XP Series crankshaft main bearing set engineered for high-load, long-duration racing applications using forged steel aftermarket crankshafts. Built on an enhanced tri-metal copper lead construction with a nickel barrier and SecureBond adhesion process, the XP Series delivers 15%–30% greater load capacity than traditional bearings — making it the choice for demanding circle track, off-road, and offshore race programs.

At the heart of the XP Series is King's proprietary pMax Black overlay — a 0.0005" metallurgically hardened performance surface that is 24% harder than any conventional tri-metal race bearing overlay. This hardening process creates a fatigue-resistant shield capable of withstanding extreme sustained loads and elevated RPM without surface breakdown.

Key Features:

• pMax Black Overlay: 0.0005" hardened tri-metal overlay — 24% stronger than competing race bearings (14.5 HV vs. 11.5 HV)
• Superior Load Capacity: 17,000 psi intermediate layer capacity and 10,200 psi overlay capacity
• 15%–30% Greater Load Capacity compared to traditional bearing designs
• SecureBond Adhesion: Unique bonding process provides superior stability between the steel backing and intermediate copper layer
• Bull's Eye Tolerance: Wall thickness variation held to ±0.0001" — the tightest in the industry — for consistent clearance and reduced assembly time
• Half-Groove Design: Upper mains are 1/2 grooved to preserve full lower shell load capacity
• Improved Oiling: Enlarged, chamfered oil holes promote consistent oil flow to critical journal surfaces
• Medium Eccentricity: Optimizes load distribution and enhances hydrodynamic lubrication
• Narrowed Design: Shells are narrowed to accommodate large-radius crankshaft fillets

Construction: Enhanced tri-metal — steel backing / copper-lead intermediate layer / nickel barrier / lead-tin-copper Babbitt overlay (pMax Black hardened)

Ideal Applications: High-load, long-duration racing including circle track, off-road, offshore, and any application utilizing a forged steel aftermarket crankshaft.

King offers the widest selection of bearing sizes in the industry, including special clearance options, ensuring you can dial in the exact oil clearance your build demands. The MB512XP is also available in undersizes and extra-clearance variants for precision engine assembly.