Edelbrock RHS LS Block 54901U-904 is a high-performance aluminum LS engine block with a tall-deck configuration for serious custom engine assembly. It is intended as a performance foundation for builders who need more architecture and strength than a production-style block can provide.

Aluminum construction, performance grade type, 9.76 inch deck height, 4.125 inch cylinder bore diameter, .904 inch lifter bore diameter, and a raised cam centerline intended to allow larger stroke. This makes it a strong starting point for LS builds where deck height, rotating assembly planning, and machining precision are central to the final combination. The tall-deck format is best approached as a precision engine-building component, with machining and assembly decisions planned around the final combination.

Edelbrock RHS LS Block 54903U-904 is a high-performance aluminum LS engine block built for serious engine builds that need more strength and capability than a standard production block. It is a foundation component for performance assembly work, not a routine service replacement.

Aluminum construction, performance grade type, 9.240 inch deck height, 4.125 inch cylinder bore diameter, .904 inch lifter bore diameter, and a raised cam centerline intended to allow larger stroke. Those details make this block relevant for builders planning higher-output LS combinations where machining, rotating assembly clearance, and block architecture matter from the start. The block is best approached as a precision engine-building component, with machining and assembly decisions planned around the final combination.