Clevite MS-685P-20 Engine Crankshaft Main Bearing Set

The Clevite MS-685P-20 is a high-performance P-Series crankshaft main bearing set designed for demanding racing and performance engine applications. This bearing set features full groove design to maximize oil flow to connecting rod bearings, making it ideal for engines experiencing rod bearing oil starvation issues.

P-Series Performance Features:

• High eccentricity design for narrower bearing contact patterns and increased rod bearing oiling
• High crush construction for maximum bearing retention in the bore
• Reduced overlay thickness to prevent overlay fatigue and hen tracking
• Full groove upper main shells for maximum oil delivery to connecting rods
• Hardened steel backing for added strength and fretting resistance
• TriMetal construction with lead-tin-copper overlay for excellent wear resistance

Best Applications:

• Engines running extremely high RPM where severe rod bore distortion occurs
• Applications showing rod bearing oil starvation (polishing, smearing, or discoloration at bearing center)
• Performance builds requiring maximum oil flow to connecting rod bearings
• Racing engines where narrower main bearing contact patterns are desired

P-Series bearings are Clevite's original high-performance bearing line, featuring unique core part numbers distinct from standard passenger car applications. The .020" oversize designation (MS-685P-20) indicates these bearings are designed for crankshafts machined .020" undersize on the main journals. These bearings do not have flash plating for improved seating characteristics and feature enlarged chamfers for better crankshaft fillet clearance.

Ideal contact patterns with these bearings should cover approximately 2/3 to 3/4 of the bearing surface. The greater eccentricity compared to H-Series bearings makes P-Series main bearings the preferred choice when narrower contact patterns and maximum rod oiling are priorities. For extreme RPM applications where bearing contact extends nearly parting line to parting line, P-Series provides the eccentric geometry needed to maintain proper oil film thickness.