King Engine Bearings MB5180AM0.25 AM-Series Crankshaft Main Bearing Set Undersize - 0.25mm

The King Engine Bearings MB5180AM0.25 is a complete crankshaft main bearing set built to King's AM-Series specification, featuring a bi-metal aluminum construction engineered for reliable performance in low to medium load engine applications. This set is sized at 0.25mm undersize, making it ideal for engine rebuilds where crankshaft journals have been machined to the first standard undersize.

King Engine Bearings' AM-Series uses a K-783 aluminum-based material equivalent to SAE-783, a proven bi-metal alloy composition designed to deliver a balance of wear resistance, conformability, and embedability. The aluminum lining alloy (Al20Sn1Cu) bonds directly to a steel backing with no overlay required, providing consistent and durable journal support throughout the engine's service life.

Key Features:

• Material: Bi-metal aluminum (K-783) — equivalent to SAE-783 industry standard
• Series: AM-Series, recommended for street and marine engine rebuilding applications
• Construction: Aluminum bearing alloy bonded to steel backing — no overlay
• Size: 0.25mm undersize for use with reground crankshafts
• Tolerance: Precision wall thickness control to ±0.0001" for consistent oil clearance
• Eco-Friendly: Lead-free construction — environmentally safe and user-safe
• Application: Suited for low and medium load gasoline engines

King Engine Bearings has been a specialist in engine bearing manufacturing since 1960, supplying high-quality bearings for automotive, marine, and other internal combustion engine applications. The MB5180AM0.25 is the correct choice for a precision engine rebuild requiring first undersize main bearings with proven aluminum bi-metal durability.