Std,.010,.020,.030 Small Block Chevy Main Bearings specify undersize

These Tri-Metal 77 engine bearings combine the strength of a copper-lead alloy layer with steel backing and an electroplated babbitt metal. The steel backing provides strength and durability; the babbitt overlay provides the critical surface characteristics of slipperiness and conformability. This ideal design has properties not even found in many original equipment bearings.

P Series
• Typically the greatest level of eccentricity
• Rods and mains have high crush for maximum retention
• Most are fully grooved to maximize oil flow to rod bearings
• Reduced overlay thickness to prevent overlay fatigue
• Use where extremely high RPMs cause severe rod bore close-in
• Use where higher eccentricity is desired to narrow bearing contact patterns