LS Aluminum Block - 4.120 Bore 9.240 D/H

The LS Aluminum Block - 4.120 Bore 9.240 D/H from Racing Head Service is engineered for serious engine builders and performance shops tackling high-displacement LS platform builds. This precision-cast aluminum block serves as the foundation for stroker engines, big-bore applications, and custom LS swaps where stock displacement limits don't meet your horsepower goals. Whether you're building a restomod muscle car, constructing a competition engine, or designing a custom powertrain for a late-model platform swap, this Racing Head Service block delivers the bore diameter and deck height necessary to maximize cubic inches and breathing room for oversized pistons and performance internals.

Manufactured from durable aluminum alloy, the LS Aluminum Block features a 4.120-inch bore and 9.240-inch deck height (D/H), allowing you to pair it with larger displacement rotating assemblies and higher-compression forging combinations than smaller-bore alternatives. The aluminum construction reduces overall engine weight compared to iron blocks, improving power-to-weight ratio and reducing parasitic losses on both naturally aspirated and forced-induction platforms. Racing Head Service maintains tight manufacturing tolerances and superior metallurgy throughout the casting, ensuring concentricity and bore finish that accepts honing and precision piston fitment without compromise. The generous deck height accommodates taller piston assemblies and extended rod ratios, giving builders maximum flexibility in stroke selection and compression ratio tuning.

LS engine builders choosing the 4.120 bore and 9.240 deck height typically target 427+ cubic-inch combinations with oversized performance pistons, forged crankshafts, and high-flowing cylinder heads for race engines, truck builds, and premium restorations. This block integrates seamlessly with standard LS family accessories—oil pans, water pumps, fuel systems, and EFI controllers—making it compatible with both carbureted and fuel-injected engine management. Installation requires precision line-honing and proper machining of the deck surface, bore, and lifter galleries; professional machine shop preparation is strongly recommended. Weighing 140 pounds, the aluminum construction supports extended rev limits and reduces overall vehicle weight, making this block ideal for performance applications where every pound matters.