Clevite MS-2218P-.25MM Performance Main Bearing Set Undersize

The Clevite 77 MS-2218P-.25MM is a high-performance main bearing set featuring P-Series construction designed for demanding racing and performance applications. This undersize bearing set (-.25MM) is engineered for engines requiring precise clearance control and maximum oil delivery to connecting rod bearings.

P-Series Performance Features:

• High crush design for maximum bearing retention in performance engines
• Hardened steel backing for exceptional strength and resistance to fretting
• Reduced overlay thickness prevents overlay fatigue and "hen tracking"
• Full groove upper shell design maximizes oil flow to rod bearings
• High eccentricity rod bearing design accommodates extreme RPM conditions
• TriMetal construction for durability under high loads

Bearing Design Technology:

This main bearing set utilizes optimized 180-degree grooving in the upper main shell to provide the best balance of oil film thickness and connecting rod lubrication. The ungrooved lower shells maintain maximum oil film thickness where loads are highest, significantly improving bearing life and safety margins. This design has been proven through extensive testing to minimize horsepower loss while reducing peak oil film pressure compared to full-grooved or extended-groove designs.

Ideal Applications:

P-Series main bearings are recommended for high-RPM racing engines experiencing severe rod bore distortion and requiring increased oil flow to rod bearings. Signs that P-Series bearings are appropriate include rod bearing oil starvation (polishing, smearing, or discoloration concentrated at the bearing center) or the need for narrower main bearing contact patterns. These bearings work best when maximum eccentricity is desired to concentrate bearing contact and enhance rod bearing lubrication.

The -.25MM undersize accommodates crankshafts that have been ground undersize for journal restoration or performance modifications. Contact patterns should ideally cover 2/3 to 3/4 of the bearing surface for optimal performance.