King Engine Bearings MB5781SI0.75 SI-Series Main Bearing Set Undersize - 0.75mm

The King Engine Bearings MB5781SI0.75 is a SI-Series crankshaft main bearing set machined to a 0.75mm undersize, engineered for engine rebuilds on the Nissan MR18DE, MR20DE, and Renault M4R 700/01/04 engines. Cross-references include interchange part number MS-2301A.

About King SI-Series Bearings:

• Silicon-Aluminum Alloy (K-788): The SI-Series material is strengthened with 2.5–3% silicon content, making it better suited for medium-load engines and nodular cast iron crankshafts than standard aluminum bearings
• Improved Crankshaft Compatibility: The silicon-enhanced alloy reduces microscopic ferrite peaks commonly found on improperly ground or polished nodular cast iron crankshaft journals
• Optimized Oil Clearance: SI-Series bearings feature improved oil clearance tolerances designed to reduce wear, extend engine life, and lower operating noise, vibration, and excess oil flow
• 100% Lead-Free Construction: Bi-metal construction using environmentally friendly, lead-free aluminum silicon — safe for users and compliant with modern environmental standards
• Bull's Eye Tolerance™ Technology: King's proprietary manufacturing process combines high-accuracy machining, overplating, and computerized wall thickness monitoring to deliver consistent, precision fitment
• 0.75mm Undersize: Designed for use with crankshafts that have been reground 0.75mm under standard journal diameter

King SI-Series main bearings are the preferred choice for OE-replacement and aftermarket engine rebuilding applications, including performance engines running factory crankshafts. Cross-reference: MS-2301A / 5M2905-STD.