Copper Exhaust Header Gasket SetBig Block Chevy 454 Square Port These Procomp Electronics exhaust gaskets are made from thick copper, and feature an embossed ridge around the exhaust port for a tight, leakproof seal. The copper gaskets help even out the flow between the head and header flange to minimize warping. Also, theyll conform to rough or irregular surfaces to maintain a positive seal, while keeping the header bolts tight.