B16 Engine poppet valve information report - Poppet valves control combustion chamber induction and exhaust gas flow in reciprocating combustion engines. Poppet valves are manufactured from iron, nickel, titanium, and cobalt-base metallic alloys that are often welded together in various combinations.
Martensitic and austenitic steels are used for intake valves. Specially designed high temperature martensitic alloys, austenitic alloys, and superalloys are used for exhaust valves.
Titanium alloys have been used for both intake and exhaust valves in some limited production, high performance applications. Special iron, nickel, and cobalt-base alloys are welded to many of the valve head alloys to improve seat face wear and corrosion resistance
The majority of intake valves for all applications are one-piece construction that also has significant usage in spark ignition engine exhaust valves.