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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.
Its primary task is to transition air between the 45-degree seat angle and the port. The throat angle also reduces the width of the 45-degree seat angle from the bottom. But thereâs much more to this than just angles. The position and width of the 45-degree seat on the valve is also crucial. For the intake valve, most head specialists like to position the seat as high (toward the chamber) on the valve as possible.