Material Specification
Intake and exhaust valves seal the combustion chamber and regulate the charge exchange process. Valves are thermally and mechanically highly stressed parts which are also exposed to corrosive influences. The mechanical stress is caused by the bending of the valve head under ignition pressure and by heavy impact during closure (shock load). There have been considerable advances in Valve designs as well as material.
Intake valves run cooler and are washed with fuel vapors which tend to rinse away lubrication on the valve stem. So for intake valves, wear resistance may be more important than high temperature strength or corrosion resistance Exhaust valves, on the other hand, run much hotter than intake valves and must withstand the corrosive effects of hot exhaust gases and the weakening effects of high temperatures. Consequently, a premium valve material is an absolute must on the exhaust side.
Materials that may be used for performance valve applications include carbon steel alloys, stainless steels, high-strength nickel-chromium-iron alloys and titanium. The alloys that are most commonly used for performance engines include various high chromium stainless alloys for intake valves and for exhaust valves are shown below.
