Wiseco K398X3905 GM LS-Series Forged Piston and Ring Set, 3.905-Inch Bore, Flat Top

The Wiseco K398X3905 piston and ring set is engineered for GM LS-Series engines using a standard-stroke configuration and a 3.905-inch bore. This kit includes forged flat-top pistons designed to provide dependable strength and consistent performance in high-performance street, competition, and engine-build applications. The flat-top crown design delivers a measured minus 3.20 cc volume, helping builders calculate compression ratio accurately during engine assembly.
The forged construction offers excellent durability under demanding operating conditions, while the 1.304-inch compression height supports proper piston positioning within compatible LS-Series combinations. The included ring package uses 1.2 x 1.2 x 3.0 mm grooves, providing a modern, low-friction configuration for efficient sealing and controlled oil management. Verify bore size, compression height, ring specifications, deck height, connecting rod length, and intended engine application before installation.
Designed as a complete piston and ring kit, the Wiseco K398X3905 helps simplify component selection for GM LS-Series builds. Its precision-focused design supports consistent cylinder-to-cylinder performance when paired with properly prepared bores and accurately set clearances. Professional installation is recommended, including measurement of piston-to-wall clearance, ring end gap, valve-to-piston clearance, and final compression ratio according to the engine builder’s specifications. This kit is not air restricted and does not require truck freight handling.

Features:

• Brand: Wiseco

• Part Number: K398X3905

• Application: GM LS-Series engines

• Configuration: Standard stroke

• Construction: Forged piston

• Crown Design: Flat top

• Bore Size: 3.905 inches

• Compression Height: 1.304 inches

• Ring Groove Configuration: 1.2 x 1.2 x 3.0 mm

• Piston Volume: Minus 3.20 cc

• Kit Contents: Pistons and rings

• Shipping Classification: Not air restricted and not truck freight only