Set of 4 Supertech 40mm (OEM) diameter intake valves with 7mm diameter x 91.60mm valve stems to fit 4cyl 8v motor.
The black nitride coating 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. Value 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 seats).
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