King Engine Bearings MB4060SI0.25 SI-Series Crankshaft Main Bearing Set Undersize - 0.25mm

The King Engine Bearings MB4060SI0.25 is a SI-Series bi-metal silicon aluminum crankshaft main bearing set ground to a 0.25mm (0.010") undersize for use on Chrysler 201ci (3.3L) OHV V6 engines requiring a reground crankshaft. This set is engineered for OE replacement and aftermarket engine rebuilding applications, delivering factory-spec fit and long-term durability.

SI-Series Silicon Aluminum Material Advantages:

• Silicon-strengthened alloy: Bi-metal construction blends aluminum with 2.5–3% silicon, optimized for medium-load engines and nodular cast iron crankshafts
• Improved wear resistance: Silicon particles round off microscopic high spots on crank journal surfaces during break-in, reducing friction and long-term wear
• Enhanced crankshaft finish: Reduces microscopic ferrite peaks on improperly ground or polished nodular cast iron crankshafts
• Tighter oil clearance control: Reduced wear helps maintain OEM oil clearances over the life of the engine, minimizing operating noise, vibration, and excess oil consumption
• Superior temperature threshold: Silicon Alecular material withstands up to 662°F (350°C), significantly higher than traditional tri-metal bearing designs
• Wall thickness tolerance: All bearing shells matched to ±0.0001" for precise, consistent fitment
• Lead-free construction: Environmentally responsible formulation with no lead content
• Corrosion resistant: Defends against corrosion caused by unleaded fuels and moisture

King Engine Bearings' SI-Series is the preferred material for OE engine rebuilding, offering a cost-effective and performance-proven alternative to traditional tri-metal bearings without sacrificing durability or reliability. The MB4060SI0.25 is sold as a complete main bearing set ready for installation.