King MB5304XP.026 XP-Series +0.026 mm Main Bearings for Mazda B6/B3/B5 Engines

Engine / Vehicle Fitment

• Mazda 4-cyl engines - B6 / B6-T / ZM / B3 / B5 (typical in 1986-2005 Mazda 323, Miata, Protege, MX-3 and related models)
• Example vehicle-engine use periods: 1986-1994 Mazda 323, 1994-2005 Mazda Miata, 1995-2000 Mazda Protege, 1995-1996 Mazda MX-3 (when equipped with B-series engines)

Features

• XP-Series "pMax Black" tri-metal main bearings - built for high-load, high-RPM, performance-oriented use
• +0.026 mm undersize bearing shells - for crankshafts machined undersize (journal re-grind) or block line-bored to undersize specs
• Precision-machined shells with tight tolerances for consistent oil clearance and reliable performance under stress
• Narrow shell design - optimized for clearance on aggressive crank fillets or modified crank geometry
• ¾-groove lower shells and chamfered oil holes - improved oil flow and lubrication under high engine load or RPM
• Tri-metal overlay with copper-lead-nickel bearing alloy - offers high fatigue resistance and durability under heavy duty or performance use
• Matched bearing set for consistent alignment across all main journals and uniform oil clearance throughout the block
• Ideal for rebuilds, performance builds, turbo / forced-induction conversions, or any build requiring undersize bearings after crankshaft machining

Specifications

• Bearing size: +0.026 mm undersize (undersized journal spec)
• Engine families: Mazda B-series 4-cylinder (B6 / B6-T / ZM / B3 / B5)
• Number of bearings: 5 pairs (complete main bearing set for 4-cylinder block)
• Material: Tri-metal alloy with pMax Black overlay for high durability
• Lower shell: ¾-groove design for enhanced oiling

Included Components

• 5x main bearing half-shell pairs (undersize +0.026 mm)

Product Description

The King MB5304XP.026 is a premium undersize main bearing set from King's XP racing line, engineered for Mazda 4-cylinder engines of the B-series - specifically B6, B6-T, ZM, B3, and B5 blocks. The +0.026 mm undersize shells make this set ideal when the crankshaft journals have been machined down (e.g., after a re-grind, blueprinting, or rebuild), restoring proper oil clearance and fitment. The high-strength tri-metal construction and optimized bearing geometry make them suitable for high-stress, high-RPM, or forced-induction builds.

With narrow-shell design, groove-type lower shells and enlarged oil passages, these bearings ensure consistent lubrication and bearing stability under high load or sustained RPM - increasing longevity and reliability compared to standard bearings. Whether you're rebuilding a stock engine that's been machined or constructing a tuned/race engine, MB5304XP.026 offers the durability and precision needed to handle the demands of performance use.

WARNING: Fitment Note: This bearing set fits engines built with B-series blocks common to 1986-2005 Mazda/B-series-equipped models (e.g., 1986-1994 Mazda 323; 1994-2005 Mazda Miata; 1995-2000 Mazda Protege; 1995-1996 Mazda MX-3). Always verify your engine block code (B6, B3, B5, etc.) and confirm crank journal diameter before installation, especially if the crankshaft was machined or re-ground.