GM Performance Big block 454 CID bare Engine block, Mark IV /Gen VI, Bare Block, bore diameter shipped 4.240 in unfinished, honed finish bore size 4.250 in ”non-Siamesed” cylinder walls, Max bore dimeter 4.310″, 9.800″ reinforced deck height, 4-bolt Mains straight grade 8 bolts, max stroke 4.250″,1-Piece Seal, Iron weight 247 lbs , roller camshaft provision, Mechanical fuel pump boss, Max hp 650, will accept Mark IV, Gen V or Gen VI cylinder heads, requires Gen V or Gen VI oil pan and timing cover, Special order item 5-7 business days. Note cylinders will need to be finished honed and all clearances checked, washed, hardware installed before put into service. Please-email with any questions and availability. (Bank wire transfer or certified check.)