Speed Pro 149M25MM - Competition Series 3/4 Grooved Main Bearing Set 4.6L Aluminum Blocks .010" Undersize

Highly Recommended for all Forced Inductions and High RPM 4.6 Engines.
These Bearings are for the Ford 4.6 Aluminum Blocks ONLY and are NOT interchangeable with the Romeo or Windsor Iron Blocks.

Building a serious competition engine? Then you'll definitely want to check out Speed-Pro Competition Series main bearings. They were developed in NASCAR and Pro Stock competition, so you know they're tough. They're built on premium 1020AK steel backings, and overlaid with Speed-Pro's super-duty H-14 alloy. 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. These 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.