Edelbrock part #7205 Exhaust Gaskets are designed for 1965-90 Big-Block Chevy Mark IV, 396-402-427-454 V8 engines. These Exhaust Gaskets are made of EnCore HTX-900; a high-density non-asbestos fiber/metal core composite material consisting of two graphite coated, heat resistant fiber blended sheets that are mechanically and chemically fused to an expanded steel core. The finished product provides high heat resistance, excellent load retention and unmatched sealing performance on exhaust manifold and header applications. A 50% recovery rate allows for gasket expansion in the event your header loses the proper header bolt torque. Gasket futures a 1.940" (round) port size.