The valve located within the cylinder head that control the flow of spent gases from the cylinder. The exhaust valves are precisely actuated (opened and closed) by the camshaft, usually through lifters, pushrods, and rockerarms. Exhaust valves must withstand extremely high temperatures (1500 degrees-F or higher) and are made from special steels, e.g., SAE J775 that has excellent strength at high temperatures and good resistance to corrosion and wear.