Professional Products Hurricane Polished Manifold with Oval Port for Big Block Chevy features a polished finish. It is designed for serious big block performance engines. The Hurricane is optimum for 396, 427 and 454 CI displacement engines producing power in the 600 to 700 horsepower range. This manifold features oval ports that can be opened up to match the gasket and/or larger port cylinder heads. It also includes nitrous bosses, four corner water ports and dual distributor hold downs. Use an 800 CFM or larger 4150 square bore carburetor.