Single Plane Split-Design Race Intake Manifold- GM LS1/LS2/LS6- Black Carbureted Single Plane Split-Design Race Intake Manifold Fits All GM LS Gen III or IV Engines Equipped with LS1/LS2/LS6 Style Cathedral Port Cylinder Heads Holley? Carburetor Flange Standard 4150 for up to 1 3 4 inch diameter throttle bores The Ls Race single plane intake manifold was designed for hi performance racing engine applications, 5. 3 to 6. 2+ liter displacement, and maximum engine speeds of 6000 7000 rpm, depending on the engine combination. This single plane design provides optimal performance across the RPM spectrum while providing maximum performance up to 7000 rpm. The new Holley Single Plane