Engines and Components› Pistons and Piston Rings

Diamond Pistons

Forged Piston Kit

$847.65

SKU: 21405

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Description

The Diamond Pistons 21405 is a forged piston kit specifically engineered for Buick 3800 L67 Series II engines. Constructed from a robust 2618 alloy, these pistons are built to withstand the demands of forced induction applications, particularly turbocharging. Key specifications include a 3.800-inch bore, a 3.400-inch crankshaft stroke, and a 5.640-inch rod length. The compression height is 1.205 inches, with the top ring positioned .240″ down from the piston crown. This kit includes premium 8620 wrist pins with a .155 wall and accommodates a standard 1.5x1.5x3mm ring package (rings not included). The calculated compression ratio with 62cc heads is 9.5:1, making it suitable for mild boost applications. Diamond Pistons, founded in 1968, has a long history of innovation in performance and racing piston design. This kit reflects that legacy, offering a reliable component for enthusiasts seeking to enhance their engine's performance.

MIA's Description

The Diamond Pistons piston kit is designed for Buick 3800 L67 Series II engines. It features a 2618 alloy forged piston with a bore size of 3.800 inches, a crankshaft stroke of 3.400 inches, and a rod length of 5.640 inches.

This kit is engineered for turbo applications and includes premium 8620 wrist pins with a .155 wall. It comes with a standard 1.5x1.5x3mm ring package and has the top ring down from the piston crown at .240″. The compression ratio with 62cc heads is 9.5:1.

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Specifications

BrandDiamond Pistons
Part Number21405
CategoryEngines and Components

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Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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