Keith Black Hypereutectic Piston Set

The Keith Black Hypereutectic pistons (KB379-030) are engineered for demanding high-performance applications, including marine, drag racing, circle track, street use, and towing. Constructed from a low-expansion 390 alloy with 16 percent silicon, these pistons allow for a tighter piston-to-wall running clearance, contributing to increased efficiency and durability. These pistons boast fully machined head and valve reliefs for optimal combustion and clearance. They come equipped with triple spiral lock rings and feature CNC-machined pin bores that ensure straight and accurately sized bores. For enhanced sealing and performance, an accumulator groove is integrated to aid the compression ring seal, and machined-in oil returns manage lubrication effectively. Further enhancing their performance, the KB379-030 pistons have diamond-finished skirts to minimize friction and wear, along with mini grooves designed to reduce scuffing and overheating. Wrist pins and spiral lock rings are included, though piston rings are sold separately (specified as 5/64 x 5/64 x 3/16). The standard bore size is 4.000 inches, with these pistons offered at 4.030 inches. The OE deck height is 9.500 inches. Compression ratios vary based on combustion chamber volume: 10.3:1 with a 55cc chamber, 9.8:1 with a 60cc chamber, 9.4:1 with a 64cc chamber, and 8.9:1 with a 69cc chamber. These pistons are designed for Ford SBF 351W engines and are specifically noted as being designed for Sportsman “N” Heads. A note advises that pre-71 blocks are .020 shorter, which may not provide enough stock to clean up.