Engine - Block Components - Bow Tie Aluminum Block

From GM Performance - This heavy duty aluminum block is 47 pounds lighter than a production rear wheel drive cast iron block. It has extra thick cylinder walls with dry nodular iron sleeves. The head bolt bosses are reinforced to improve head gasket sealing. This block has wider main bearing buldheads than a production cylinder case; four bolt cps are installed on the two intermediate main bearings. These billet steel main caps have splayed outer bolts that provide additional bearing support.