W124 602 valve & Seat Machining ?

[Chris_]

Hello,

602 valve job in question...
Are the valves & seats hardened with any method that requires a specialized
machining process beyond the normal scope of a standard well equipped machine shop.
In other words will the sealing surfaces be compromised in strength by being machined

( the reason I ask is SAAB uses a stellite hardening process on the exhaust valves which once cut through turns the valve to junk )

thanks