Dart Big M Iron Block (Big Block Chevy)

OverviewIf you want a BBC block that can handle big horsepower, the Dart Big M block is for you!  With multiple deck heights and bore sizes up to 4.600", the Big M block gives you the versatility to build a wide variety of engine combinations for street, race or marine. Dart's maximum recommended bore and stroke allows displacements up to a massive 638 cubic inches (4.6125" x 4.75"). A true priority main oiling system oils the main bearings before the lifters for extra reliability. Features:-  Standard 9.800" and tall 10.200" deck heights available for stroker engines.-  Standard 4.250", 4.500", 4.560" or 4.600" bore sizes with siamesed extra thick cylinder walls to resist cracking and improve ring seal (minimum .300" thick with 4.625" bore).-  Uses +.300" tall Gen VI style lifters. Modification for Gen IV style available.-  Scalloped outer water jacket walls improve coolant flow around the cylinder barrels to equalize temperatures.-  4 bolt main steel caps have splayed outer bolts for