Made as a one piece forged valve for higher strength and reliability, Wossner use mostly EV8 (21-4N) for Intake and Exhaust valves but there are other alloys that we use along with different heat treatments to manufacture valves for different applications.
This is a hardening treatment that even though it is not widely used as the chrome coating, it has several benefits and is becoming very popular, mainly for European and Japanese applications.
The microhardness is higher than the stainless steel base material, keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum). Surface finish is smoother than with chromed stems, having less friction between stem and guide.
Valve seat surface is harder with the nitrided layer, lasting longer with lead free fuels, alcohols, nitro or other "explosive" mixes. Matches any kind of seats (nodular iron seats, steel powder metal seats, hard aluminum-copper seats or beryllium copper seat.
This is a box of 8 inlet and 8 exhaust valves...
Renault F4R 2.0 16v
Inlet - 33.5mm (OE)
Exhaust - 29mm (OE)
Both valves have flat faced heads
Inlet - 5.47mm
Exhaust - 5.44mm
Inlet - 110.5mm
Exhaust - 108.9mm
||Black nitrided stainless steel