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Valve Jobs Done Right. A close-up of a Honda CB750 SOHC valve seat. Though the upper 30 degree and the lower 60 degree shapes have been rough cut using Neway cutters, the 45 degree cut in the middle, the one that counts because it is the actual sealing surface, has the benefit of a stoned surface, the best possible with hand tools. Ah, valve jobs.
Rebuilding Cylinder Heads: Valve Grinding. Seat Work. In ancient times (about 20 years ago), seat preparation was performed using a series of grinding stones to establish the seat angles. Generally, this involved three stones that were dressed at the specific angle required.