Overview
If 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 inches, 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 in; x 4.750 in). 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 extra strength. (Big M Sportsman = ductile iron caps)
- True priority main oil system lubricates the main bearings before the lifters. Our stepped main oil gallery (9/16; to 1/2 to 7/16) increases the flow of oil to the crank at high rpm, and our front oil crossover eliminates internal oil leaks around the distributor shaft.
- Oil filter pad is drilled and tapped for an external oil pump.
- Lifter valley head stud bosses prevent blown head gaskets.
- Rear main cap uses standard oil pump and two piece seal - no adapter required!
- Mechanical fuel pump boss, clutch linkage mounts, and side and front motor mounts simplify installation in any chassis.
- Dual oil pan bolt patterns fit standard and notched oil pans.
- Small bore 396 version available
- Parts kit included for Big M; cam bearings sold separately
These blocks are available in any level of finish from ready for "as-produced" to fully machined to a complete custom crate engine. Whatever your needs, we can help.
Optional fully prepped block ready for assembly includes:
-Square deck to height and CNC chamfer cylinders on our 4-Axis Rottler CNC
-Deburr entire block & main caps
-Diamond CNC hone
-Align-hone mains, hone lifter bores
-Final clean block and paint with primer in your choice of colors
-Install cam bearings & test fit cam
-Install oil galley and freeze plugs
Our 4-axis CNC boasts precision of 0.0002 in and one thousandth of a degree. Check out this Instagram time-lapse video of a probe cycle. Honing is arguably the most critical machining operation. Check out the video below to see how we would hone your block.
Please call us at 815-725-2727 for questions and pricing on finish machining, short blocks, long blocks or full crate engines.
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