Smeding Performance is now offering the all-new aftermarket Aluminum 6-Bolt LS Engine Block, engineered for racers who demand a stronger, more capable foundation for today’s high-performance LS builds. Designed to withstand the extreme cylinder pressures and RPM levels common in modern race applications, this aftermarket block delivers the strength and oiling efficiency needed when a production block simply isn’t enough.

Available in Water-Jacketed and Solid — No Water Jackets configurations, the block lets you choose the construction that matches your application. Pick Water-Jacketed for builds that need circulating coolant to manage heat during sustained operation. Choose Solid — No Water Jackets for specialized, short-duration racing combinations that prioritize cylinder support over conventional block cooling. Select your configuration using the Block Construction selector, and review the specifications below for differences in standard head-stud threads and compatible hardware.

Cast from high strength aluminum alloy, the block provides exceptional strength, rigidity, and durability. A set of billet steel main caps comes standard, utilizing a 4-bolt splayed main cap design with 7/16-inch fasteners for increased bottom-end stability and clamping strength.

The cylinder heads are secured with an upgraded 6-bolt head bolt configuration, providing additional clamping force to help maintain head gasket integrity under extreme cylinder pressures. This makes the block an ideal foundation for high-output naturally aspirated, boosted, and other demanding race applications.

The oiling system has also been significantly upgraded with a three-galley oiling design. This configuration provides the crankshaft and connecting rods with a dedicated oil circuit, improving oil distribution and reducing the demands placed on the main oiling system. The result is a more efficient and robust lubrication system designed to support the extreme RPM levels found in today’s high-performance race engines.

Choose Your Block Construction

Solid means no water jackets in the block. Select the casting appropriate for your engine's cooling requirements. For the water-jacketed version, contact Smeding Performance about available 1/2-inch head-bolt machining and matching hardware before ordering.

Shared Specifications

• Rough bore diameter: 4.120 inches
• Maximum bore diameter: 4.185 inches
• Deck height: 9.240 inches
• Cylinder length: 5.750 inches
• Block material: cast aluminum alloy
• Six-bolt head configuration
• Main caps: billet steel, four-bolt splayed design
• Main-cap fasteners: 7/16-inch studs
• Oiling system: priority-main three-galley
• Lifter bore: 0.842 inch
• Thrust plate included
• Block plug kit included

Prep Package

The prep package includes final plateau honing to 4.125 inches, cylinder deburring, hot-tank cleaning, cam-bearing installation, and oil-plug installation.

Compatible Parts

• Head-stud kit: ARP 234-4341 for standard water-jacketed block; Dart 66130128B for solid block
• Cam bearings: Dura-Bond 32210101T
• Main bearings: King MB5777XP
• Rear main seal: GM 12639250

When the goal is to build a serious LS engine capable of handling increased power, cylinder pressure, and RPM, the Smeding Performance Aluminum 6-Bolt LS Engine Block provides the foundation to do it right. Choose your block construction to match your build.