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Features:
- Ductile iron 4-bolt mains caps for ultimate bottom-end strength
- Siamesed extra thick cylinder walls to resist cracking and improve ring seal (minimum .300 in. thick with 4.625 in. bore)
- Uses +.300 in. tall GM Gen VI style lifters
- Crankshaft tunnel has clearance for a 4.500 in. stroke with steel rods without grinding
- Main bearing caps have splayed outer bolts for extra strength
- True priority main oil system lubricates the main bearings before the lifters
- Stepped main oil gallery (9/16 in. to 1/2 in. to 7/16 in.) increases the flow of oil to the crankshaft at high RPM, and front oil crossover eliminates internal oil leaks around the distributor shaft
- Lifter valley head stud bosses prevent blown head gaskets
- Dual oil pan bolt patterns fit standard and notched oil pans
- 220 BHN cast iron block material
- .842 in. lifter bores
- Press-fit freeze plugs
- 2-Piece rear main seal
- Includes block parts kit 301-32000002 - coated cam bearings, freeze plugs and dowel pins
Emissions Note:
This part is only legal for sale and use on Uncontrolled (Non-Emissions Controlled) Vehicles or on vehicles used solely for the purposes of closed competition racing.
CLICK THIS LINK FOR IMPORTANT CARB & EPA EMISSIONS INFORMATION ABOUT THIS PART
The Strongest and Most Reliable Big Block Available!
Dart has reinvented the "Rat Motor" with their cast-iron Big M big blocks. Working with top builders and Dart's own championship-winning Pro Stock engine department, they have designed a no-compromise, user-friendly block that solves the problems that have plagued big-block racers for years. Each unit is in-house machined on precision CNC equipment to ensure the highest quality and to eliminate the need for expensive blueprinting.
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The Dart Big Block Chevy Big M Engine Block is a purpose-built foundation for serious horsepower, engineered for racers and high-performance builders who demand strength beyond OEM limits. Designed specifically for extreme big block applications, the Dart Big Block Chevy Big M Engine Block delivers reinforced construction, expanded displacement capability, and race-ready durability. Whether you’re assembling a high-horsepower street engine or a competition-only drag racing build, this aftermarket engine block provides the structural integrity needed to handle substantial torque capacity and cylinder pressure.
Unlike factory castings, the Big M block is engineered with thicker cylinder walls, priority main oiling, and reinforced main webs to support elevated horsepower levels. For enthusiasts pushing forced induction, nitrous, or large cubic inch combinations, starting with a high-strength performance engine block like the Big M is critical to long-term reliability and consistent results.
Performance Benefits & Key Features
The Dart Big Block Chevy Big M Engine Block is manufactured from premium high-strength cast iron to withstand extreme loads and high RPM use. Key features often include siamese cylinder bores for increased displacement potential, four-bolt or cross-bolted main caps for added bottom-end stability, and priority main oiling to ensure consistent lubrication under racing conditions.
Performance builders value specifications such as bore size flexibility, deck thickness, improved oil control, and compatibility with stroker rotating assemblies. These attributes allow for large cubic inch combinations capable of producing significant horsepower and torque. Enhanced rigidity reduces block flex, supporting improved ring seal and long-term durability in high-output builds.
This block is ideal for drag racing applications, high-performance street builds, marine engines, and competition-oriented projects where power levels exceed stock limitations. It’s particularly well-suited for naturally aspirated big cubic inch engines as well as supercharged or turbocharged combinations requiring a robust bottom-end foundation.
Fitment, Compatibility & Applications
The Big M engine block is designed for Chevrolet big block compatibility, making it a natural fit for custom builds based on GM big block architecture. Popular applications include classic muscle cars such as Chevelle, Camaro, Nova, and full-size Chevrolet models, along with C10 and other GM truck platforms configured for big block installation.
Engine builders appreciate the block’s flexibility for stroker assemblies and high-performance cylinder head combinations, making it adaptable for both street performance and dedicated race vehicles. Its compatibility with standard big block Chevy components allows experienced builders to tailor the engine to specific displacement and performance goals.
When you’re building serious horsepower from the ground up, start with a proven foundation. Explore the Dart Big Block Chevy Big M Engine Block options at JEGS and choose the strength and precision your high-performance build demands.
