Edelbrock RHS 54903U-904 LS Aluminum Race Block Ready to Hone 9.240" Standard Deck 0.904" Lifter

The Edelbrock RHS 54903U-904 is a high-performance aluminum LS race engine block engineered for demanding race and street performance builds. This standard deck configuration features a 9.240" deck height and is supplied ready-to-hone, allowing engine builders to finish the 4.120" bores to their exact specifications.

Built under the RHS® (Racing Head Service) brand, this block is purpose-designed to overcome the limitations of factory GM LS block designs. A raised cam centerline combined with outboard priority main oiling provides generous rod clearance for strokes up to 4.600", making it an ideal foundation for big-inch LS builds. Each block undergoes a CT scan (similar to a medical CAT scan) for quality assurance, ensuring maximum casting precision and consistency throughout.

Key Features:

• 0.904" lifter bores for oversized lifter compatibility (accepts 1.060" bushing for keyed lifters)
• 55mm roller bearing cam bores — accommodates stock through oversized 60mm roller bearing cams with cast-in lock screw pads
• 9.240" standard deck height with 5.87" cylinder sleeve length
• 4.120" bore — ready to hone, requires final finish hone before assembly
• Supports up to 4.600" stroke with engineered rod clearance as standard
• 6 head bolt design with full water jacket around the cylinders, based on the LS7 layout
• Gen III/Gen IV compliant with race mounts for Gen I, Gen II, Gen III, and Gen IV engines
• ARP main stud kit included; castings have sufficient material to accommodate up to a 1/2" fastener
• Significantly increased windage passage area under bores and around caps versus LS7/LSX engines
• Bay-to-bay breathing improved with increased side window area versus LSX and LS7
• Extra large valley windows for access to the inboard 6th head bolt
• Provisions for Gen III and Gen IV cam and knock sensors and valley covers
• Side oil gallery moved outboard for improved rod clearance and reduced windage
• Extra surface material throughout for custom machining flexibility

The RHS 54903U-904 sets a new benchmark for LS platform horsepower, torque, and durability. Note: This block is not for sale or street use in California or other CARB-regulated states.