The Performer Vortec is a dual-plane design that is tuned for maximum air flow from idle to 5500 rpm. Designed specifically for use on 1996-present Chevy 4.3L V6 Vortec engines in a marine application. One of the unique features is the brass lined water crossover and inserts to help protect the aluminum from salt-water corrosion and eliminate electrolysis in fresh water applications. It also features a carburetor flange that readily accepts square-bore and spread-bore carburetors. The Performer Vortec V6 Marine intake manifold is engineered to deliver maximum power and a broad torque curve for high-performance marine applications. Similar to the stock intake manifold, it includes a provision for 1/2 pipe water fittings on the front water crossover and 3/8 pipe horizontal vacuum fittings in the rear. Does not have a provision for an exhaust crossover, so an electric choke is required. Intended for marine use only and is not for street applications. Carburetor Recommendations: Edelbrock Marine Series carb 600 cfm and Q-Jets. Installation Notes: Recommended intake gasket: GM 89017866. Manifold Dimensions: A-3.60", B-4.44"; Carb pad height: 4.02", CA-3°. Port exit dimensions: port exit is 2.05" tall with slanted side walls.