S&S Black Cylinder Head Kit 106-4570 Fits Evolution Big Twin Engines

Description

The S&S Cycle Performance Replacement Cylinder Heads are designed for Evolution Big Twin engines (1984-1999 models), offering enhanced performance for smaller displacement engines. These heads are optimized to work with stock-style flat-top pistons and feature an 82cc combustion chamber that slightly increases compression ratios (8.8:1 in 80″ engines and 9.5:1 in 96″ engines). The precision-engineered port design improves airflow while maintaining velocity for better performance. The kit comes fully assembled with stainless steel valves (1.90″ intake and 1.75″ exhaust) and high-lift (.585″) springs, supporting a maximum lift of .585″. These heads are EFI-compatible and designed to use the stock intake manifold. Intake manifold and gasket kits are sold separately. The gasket kits include head gaskets, base gaskets, and exhaust pipe gaskets but exclude rocker box gaskets, as rocker box styles vary.