4.050" Bore Recessed Head Piston

The Sealed Power 381NP40 is a cast aluminum piston engineered for engine rebuilding and restoration projects. This piston is designed to meet or exceed original equipment manufacturer (OEM) specifications, ensuring reliable performance for applications over 35 years old. It features a precisely controlled casting, heat-treating, and CNC-machining process for durability. Key specifications include a 4.0500-inch (101.6mm) bore diameter and a 1.660-inch compression height. The piston pin diameter measures 0.975 inches, and it is designed for piston ring thickness of 5/64 in. x 3/32 in. x 3/16 in. This particular piston is oversized by 0.040 inches. It features a recessed head type and is not file-fit or gapless.