Ultra-Seal Header Gaskets Fits 1955-1991 Chevrolet 262-400 Gen I Small Block D-Shaped Ports, 1.55 Inch x 1.71 Inch Mr GasketManufactured from high temperature steel core graphite faced exhaust material. Expanded steel core provides stability and maximum torque retention to eliminate Gasket failure. Graphite facing provides excellent heat resistance and thermal conductivity to transfer heat away from the cylinder head. Conforms to and seals minor surface irregularities. High recovery material allows header or manifold flange to stay sealed if flange loses clamp load. Can be