Reconditioning Or Replacing Valve Seats

After installing valve guides, valve seats must be refacedto true them with guides.

Figure 3-4. Compressing Valve Spring

If valves have been reseated several times, valve seats may have become too wide and/or valve may be seating itself too deeply in head. When valve seat becomes wider than 1/16 in. (see Figure 3-5) valve seat relief must be counter-bored or ground to reduce seat to 1 /16 in. Counterbore dimensions are shown. Tools for this purpose are available commercially. To determine if valve is seating itself too deeply in head, measure distance from shoulder of valve guide to end of valve stem. See dimension in Figure 3-5. When valve stem extends through guide excess of maximum shown valve seat inserts must be replaced.

A special gauge is available under Part No. 96490-59A which is used to measure this dimension. The tool consists of gauge valves and gauge which is placed over the valve stem as shown. If top end of gauge valve stem is between steps on gauge, the valve seat location is satisfactory.

Replacement inserts are available from the factory. Installation requires accurate boring equipment to machine correct counterbore in head for installation with .004 to .006 in. interference fit.

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