New Sealed Power Nissan 300ZX intake valve coating remove?

[Heptec]

Should I grind the intake valve faces and remove the black coating or just instal them as is. I chucked them in the grinder and they show no runnout with a last word indicator (0 to 0.001&quot and the finish is visually smooth using a 500x surface comparator.

 

[evelrod]

I don't know about your specifics but I have used many sets of suitably modified L-18 exhaust and L-20 intake valves in my Lotus twincams in the past. Any machine work removed the 'black' coating but that's about it. Never bothered to polish the valves after the first set was flowed. The polishing added nothing on the dyno so why bother? I stuck with the Nissan 8mm stems as it was quick and easy to oversize the guides.

Rod