Chevy SB, DUROSHIELD Coated .030 over Main Bearing Set Speed-Pro Competition Series 3/4 Groove, Tri Metal

C139M30 are Sold as a Set Fits Chevy 327, 305, 350, Large Journal STD Size

DUROSHIELD Competition Series Coated Bearings provide protection against dry starts and conditions that interrupt oil supply. Speed-Pro’s H-14 Super Duty Alloy has the greatest load-carrying capacity. Speed-Pro's H-24 Alloy is notable for its desirable fatigue resistance and strength.

Speed-Pro Competition Series main bearings were developed in NASCAR and Pro Stock competition. Speed-Pro Competition Series main bearings H-14 Lining material that is bonded to a premium 1020AK steel backing. That's covered with a nickel barrier, followed by a thin lead-tin-copper overplate. However, unlike other performance bearings, there is no flash tin layer on top of that.

Speed-Pro's engineers have determined that such a layer can actually move around under high loads--sometimes with undesirable consequences. The key to reducing fatigue wear in bearings is to keep the overplating thickness to a minimum

Speed-Pro Competition Series main bearings have 3/4 oil grooves for enhanced lubrication, while maintaining a maximum bearing surface area. They also feature Speed-Pro's exclusive contoured-flange thrust bearing technology for higher thrust-loading capacity.