B58/S58 Copper gasket with fire ring (resuable)
 
Copper is the standard for conductors, in head gaskets we don’t care about electricity but we do deal with heat. Superior conductivity benefits performance and racing engine builders in two primary ways: A. block & head temperatures are more even. B. Combustion chamber hot spots are dissipated quickly. Cylinder block/head temperature parity is an aid to tuning, though frankly, it’s a minimal factor until you reach the narrow end of the tuning window. The big advantage of conductivity is in the combustion chamber area. In and around the combustion chamber standard composite head gaskets and MLS head gaskets are somewhat insulated from the cylinder head and block by the facings and coatings respectively. Heat-related failures occur more often with composite and MLS head gaskets than with copper because the heat is trapped within the gasket body allowing hot spots to intensify, whereas the copper being both a better conductor and having direct contact with the block and head (remember metal-to-metal) transfers the heat to the heat exchanger, aka the cooling system, through the head and block.
 
Another interesting feature of copper, this benefit comes into play when you’re out of the tuning window far enough to actually damage the head gasket. Un-alloyed or pure copper has a 25% coefficient of elasticity; cool term, here’s what it means. In a 4 inch section, the copper head gasket will stretch to 5 inches before it ruptures. This gives the user a ‘safety factor’ not available with other head gasket materials. Blown, nitrous or turbocharged engines can develop cylinder pressures high enough to lift the cylinder head or push the gasket.  If this happens with copper the damage is apparent but the head gasket hasn’t yet failed. The safety factor of elasticity allowed the copper gasket to push but still remain intact so you can either back it down & make the next round or back it down & drive home. 
 
Proven and tested over 50psi of boost and 1250HP
 
Thickness 0.043"
83mm bore max on b58
85mm bore max on S58