GM 5.7L Aluminum LS1/LS6 Blocks (Bare block) are direct replacements for the 2001-04 LS1 and LS6 Corvette 5.7L engines. Manufactured from 319-T5 aluminum, they use cast iron sleeves, the production oiling system, and 6-bolt main bearing caps. The GM Performance 5.7L LS1/LS6 aluminum engine blocks feature a 9.240 in. deck height and accept LS1/LS6-style cylinder heads only. The blocks feature a finished bore of 3.980 in. and do not include a provision for Active Fuel Management.