Main Bearing Set.

The King Bearings Main Bearing Set (MB 557SI 001) is engineered for small block Chevy engine rebuilds and high-performance modifications where precision crankshaft support is non-negotiable. This bearing set addresses the critical need for proper load distribution across the crankshaft's main journals, ensuring reliable power delivery during both street and competition use. Whether you're freshening a tired engine or building a stroker, quality main bearings are foundational to longevity and consistent performance.

Manufactured by King Bearings—a trusted OEM and performance bearing supplier—this set features a 0.001 inch undersize specification, which accommodates crankshafts that have been lightly polished or refinished to restore journal diameter after wear or damage. The Alecular SI construction provides excellent embedability and conformability, protecting against micro-seizing while maintaining optimal oil film strength under sustained load and elevated RPM. The compact kit dimensions (3.7 x 1.85 x 5.5 inches) reflect a complete small block set ready for installation.

Mechanics and engine builders working on Chevy small blocks benefit most from this bearing set during full rebuilds where crank journals have been machined to 0.001 inch undersize tolerances. Installation requires careful attention to bearing cap torque specifications and proper oil clearance verification—typically 0.0015–0.0025 inches for small block applications. Pairing this set with quality engine oil, fresh gaskets, and correct assembly procedures ensures maximum bearing life and engine reliability for thousands of miles.