Square Port header gaskets for Gen I small block Chevrolet engines, built with a high-temperature expanded-steel core to maintain stability, resist blowout, and hold torque even under extreme exhaust heat. The graphite-impregnated facing conforms to small flange irregularities, transfers heat efficiently away from the cylinder head, and prevents sticking during removal. The high-recovery material helps maintain a seal if the header flange loses clamp load, and the gasket can be trimmed for modified port configurations. Suitable for OE replacement, performance street engines, drag racing, and oval-track use.