The Edelbrock Centerbolt Performer 50-State Street Legal Aluminum Cylinder Head was originally equipped with centerbolt valve covers and the 1987 and later intake manifold bolt pattern. The high-velocity intake runner of this head is designed to work with either T. B. I. or Tuned Port Injection systems. It uses the 1987-1995 intake manifold bolt pattern and maintains stock compression ratio when used with the recommended head gasket. It accepts stock or aftermarket valve covers. The 60cc combustion chambers maintain the stock compression ratio when used with the recommended head gasket. They come with 2. 02" intake valves and 1. 60" exhaust valves with intake port which measures 165cc. The ports feature stock location for compatibility with stock intake manifolds and standard headers and the CNC port matched intake and exhaust ports are for optimum flow and maximum power. It accepts stock centerbolt valve covers and comes with a straight plug configuration.