GM Performance Engine Block, Aluminum, 6-Bolt Mains, 4.117- 4.160 in. Bore, 1-Piece Rear Main Seal, Chevy, Small Block, Each (PART #GMP-12480030)

GM Performance Bowtie aluminum C5R Gen III engine blocks are the same blocks that were used in the LeMans 24-hour endurance racing C5R Corvettes and are intended for maximum-effort competition engines. They have the same production external dimensions and bosses; the primary difference of this block to the Gen III production blocks is the siamesed water jacket, which allows engine builders to build engines with larger bore sizes. The GM Performance Bowtie aluminum C5R Gen III engine blocks feature a cylinder deck height of 9.240 in. and use a dry, pressed-in liner similar to other GM Racing aluminum small blocks. Other features include steel billet main bearing caps, wet sump style oiling, and high-strength A356 aluminum that utilizes a modified T7 heat treatment. You are guaranteed durability, reliability, and high performance by using one of these GM Performance Bowtie aluminum C5R Gen III engine blocks.