Edelbrock 54901U-904 RHS LS Aluminum Race Block 9.750" Tall Deck 4.120" Bore 0.904" Lifter

The Edelbrock RHS LS Aluminum Race Block (Part #54901U-904) is a competition-grade, tall deck engine block engineered by RHS® (Racing Head Service) for GM LS applications. Constructed from heavy-duty A357-T6 aircraft-quality aluminum, this bare block is machined and ready for final finish honing, making it the ideal foundation for serious race and high-performance street engine builds.

This tall deck variant features a 9.750" deck height and a semi-finished 4.120" bore with siamese cast bore walls (4.125"–4.165") reinforced by press-in spun cast iron liners. The block is specifically machined for 0.904" lifter bores, with additional material available to accommodate 1.060" bushed keyed lifters. A raised cam centerline and outboard priority main oiling system provide the rod clearance necessary for strokes up to 4.600" while minimizing crankcase windage.

Key Features:

• Heavy-duty A357-T6 aluminum construction for maximum strength-to-weight ratio
• 9.750" tall deck height with a beefy .750" deck thickness
• Semi-finished 4.120" bore — requires final finish hone before assembly
• 0.904" lifter bores standard; accepts 1.060" bushing for keyed lifters
• 55mm roller bearing cam bores to accommodate stock through oversized camshafts
• Raised cam centerline engineered for up to 4.600" stroke clearance
• 6.38" tall deck cylinder liner length
• 6-bolt main cap design with full water jacket around cylinders (based on LS7 design)
• 8620 billet steel main caps with maximized mating surface area and large fillets for added strength
• ARP main studs included; P1 MFG main stud kit standard with material for up to 1/2" fasteners
• Outboard side oil gallery for improved rod clearance and lubrication
• Significantly increased windage passage area vs. LS7/LSX blocks
• Bay-to-bay breathing improved with increased side window area vs. LSX and LS7
• Provisions for Gen III and Gen IV cam sensors, knock sensors, and valley covers
• Machined for Gen III and Gen IV front engine mounts; provisions for Gen I mounts spot-drilled
• Provisions for front motor plate race mounts
• Ampco 45 cam thrust plate and aluminum rear cover included
• Freeze plugs included
• Each block undergoes a CT scan (similar to a medical CAT scan) for maximum casting precision and consistency

The RHS LS Race Block sets a new benchmark for LS horsepower, torque, and durability. With extra surface material for custom machining, precision computer-aided design, and unmatched finishing quality, this block is purpose-built for builders who demand the most from their GM LS platform.