Clevite MS-909H-30 High Performance Main Bearing Set

The Clevite MS-909H-30 is a high-performance main bearing set designed for demanding racing and competition engines. This H-Series bearing features a 180-degree upper half groove configuration that optimizes oil film thickness while providing adequate oil supply to connecting rod bearings.

H-Series Performance Features:

• Medium eccentricity design for optimal load distribution and contact patterns
• High crush for maximum bearing retention in performance applications
• Hardened steel back construction for added strength and durability
• Thin overlay to prevent overlay fatigue under high-stress conditions
• Enlarged chamfers for increased crankshaft fillet clearance
• No flash plating for improved bearing seating
• TriMetal construction for legendary Clevite strength and durability

Why 180-Degree Grooving?

The 180-degree upper shell groove design represents the optimal balance between oil delivery and bearing performance. This configuration maintains a thick oil film on the loaded lower bearing surface while the grooved upper shell supplies oil to the connecting rods. Extending grooves into the lower bearing half breaks up the critical oil film and increases peak oil film pressure, reducing bearing life and increasing horsepower loss.

Application Guidance:

H-Series bearings are ideal for medium to high RPM engines with oversize crankshaft fillets. These bearings were developed primarily for NASCAR-type racing but are suitable for all competition applications. The medium eccentricity provides broader contact patterns than P-Series bearings—ideal when narrower contact patterns prove insufficient. Contact patterns should cover approximately 2/3 to 3/4 of the bearing surface for optimal performance.

H-Series bearings are the recommended starting point for most performance applications where bearing selection is uncertain. They offer an excellent balance of oil flow, load capacity, and durability for serious competition use.