Supertech valves are made from one piece of forged stainless steel and go through a special heat treatment process that obtains the right amount of harness for each engine to ensure the ultimate valve for your 4B11 motor.
Black Nitride Features:
The “Black Nitride” is a hardening treatment that is applied to the whole valve while the chrome coating is only applied to the stem.
The microhardness is higher than the stainless steel base material, keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum).
The Black Nitride surface finish is smoother than with chromed stems, having less friction between stem and guide. The higher the engine speed the bigger the power loss due to internal engine friction! The Black Nitride reduces this power loss due to less valve-guide friction.