Round Port header gaskets for Gen III/IV LS engines, built using a high-temperature expanded-steel core to maintain stability and strong torque retention under extreme exhaust conditions. The graphite-impregnated facing conforms to small flange irregularities, resists heat, and helps transfer thermal energy away from the cylinder head for improved durability. The high-recovery material maintains a seal even if the flange loses clamp load, and the gasket can be trimmed for modified port shapes when needed. Suitable for OE replacement as well as performance-oriented street, drag race, and oval-track engines.