Supertech Black Nitride Valves for EJ WRX/STi

Supertech black nitride exhaust and intake valves for EJ20/EJ25 Subaru WRX and STi. These valves are available in various sizes to match your head diameter. Sold as a set of 8 or individually as needed. Please do all your research and consult your engine builder if necessary! Black nitride valves are made from one piece forged stainless steel then go through a special hardening process to lessen the friction between the valve and guide.

Vehicle Fitment:
2002-2014 Subaru WRX
2004-2021 Subaru STi

The "Black Nitride" is a hardening treatment that is applied to the whole valve whereas 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.
Images are for reference.

Note:
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