Aluminum C5R Racing Block


  • Premium “hipped” and X-rayed 356-T6M aluminum-alloy block casting
  • 6-bolt dowel-located steel main bearing caps
  • 4.117″ finished bore; 4.160″ maximum bore
  • For use with any LS or LSX series head


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SKU: 12480030 Categories: , ,

Aluminum C5R Racing Block

The ultimate GM Performance aluminum LS block, the C5R was originally designed for the Chevrolet factory-backed Corvette racing program. It was developed to support more than 440 cubic inches and up to 900 horsepower – and it proved itself by powering the Corvette team to wins at LeMans, Daytona and nearly every track they encountered. This is a non-production, purpose-built cylinder block manufactured with proprietary materials and machined to the highest tolerances – and using premium, racing-spec hardware. If you’re looking for the ultimate aluminum cylinder block to support your horsepower desires, the race-proven C5R is it!

P/N 12480030

  • Premium “hipped” and X-rayed 356-T6M aluminum-alloy block casting
  • 9.240″ deck height
  • Production-style oiling system
  • 6-bolt dowel-located steel main bearing caps
  • 340 premium map cap fasteners
  • For use with any LS or LSX series head
  • Unique cylinder liner material for maximum durability
  • Siamesed cylinders to support larger bores
  • 4.117″ finished bore
  • 4.160″ maximum bore
  • Fully blueprinted and squared
  • Production camshaft location and cam bores
  • Includes premium head studs
  • Anodized aluminum O-ring core plugs
  • No Active Fuel Management provisions
  • Supports more than 900 horsepower

Note: HIP is the acronym for Hot Isostatic Pressure. This process puts the blocks in a sealed vessel where a vacuum is first used to remove room air and any possible contaminants. The vessel is filled with high pressure nitrogen (up to 30,000-psi) and then heated to the required temperature and sustained for a determined amount of time. The cooling process is also a controlled procedure to ensure maximum strength and proper heat treat. This extreme high pressure and heat removes almost 100% of the internal porosities that are generated during the casting process. The material integrity, strength and fatigue life increases significantly.

Weight 109.7 lbs

Aluminum C5R Racing Block

12480030 Chevrolet Cylinder Block

The Chevrolet Performance LS-Series cylinder block is the foundation for the serious performance achievements that are driving a new generation of street and racing enthusiasts. Features include a deep-skirt casting (the block side extends below the crankshaft centerline); 6-bolt cross-bolted main caps, strong and lightweight aluminum alloy casting (most production blocks) and provisions for the latest in engine control management. The cam-in-block configuration brings inherent torque to every LS engine, with production-based blocks capable of supporting combinations of 500 horsepower or more. The Corvette ZR1’s unique 6.2L block, for example, supports the engine’s 638-horsepower rating. Chevrolet Performance’s high-performance iron LSX cylinder block supports more than 2,000 forced-induction horses!

Whether you’re building a mild street engine or an Outlaw racing engine, starting with a strong LS cylinder block brings the assurance that you’ll make the power you need with a durable foundation.

GM Parts and Components carry a 12-month parts-only limited warranty unless otherwise noted.


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Prop65WARNING: These auto parts can expose you to chemicals including phthalates and lead. Installing or using these parts can expose you to other parts containing these chemicals and to engine exhaust, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to