The 300-261 intake manifolds are designed for square-bore carburetor applications on 1957-86 262-400cid Small Block Chevrolet engines and SBC engines equipped with 1987-91 L98 aluminum Corvette cylinder heads (non-EGR applications). Also, these manifolds will work with any SBC engine equipped with aftermarket cylinder heads, as long as they have a standard port flange opening and mounting bolt locations. The new single plane intake manifold is designed to provide a broad RPM powerband for high-performance street/strip engine applications to a maximum engine speed of 7500 RPM. The carburetor-mounting pad is designed to accept all stock or aftermarket square-bore carburetors with manual or electric chokes. These intake manifolds are designed to accept most stock hardware and accessory brackets, but offer performance features, like an updated plenum divider area, a 1" shorter height than the 300-25 manifold, and a choice of two distributor clamp locations. The isolated design of the air/fuel passages helps to increase charge air density and performance.