D . Move the stem of the valve from side to side using light pressure to obtain a clearance reading. If clearance exceeds specifications, ream the valve guide bores for oversize valves as outlined later. 2 . Valve spring tension. Use J 8056 or equivalent. • Compress the springs, with dampers removed, to the specified height and check against the specifications chart. • Springs should be replaced if not within 44 N (10 lb.) of the specified load. 3 . Valve spring length. Replace the spring if the length is not as specified. Figure 12-50 Cleaning the Combustion Chambers Figure 12-51 Measuring Cylinder Head Surface Measure Tools Required:
J 8001 Dial Indicator (or equivalent) J 8056 Valve Spring Tester 1 . Valve stem to guide bore clearance. NOTICE: Excessive valve stem to guide bore clearance will cause excessive oil consumption and may cause valve breakage. Insufficient clearance will result in noisy and sticky functioning of the valve and disturb the engine's smoothness. A . Clamp a dial indicator (J 8001 or equivalent) on one side of the cylinder head rocker arm cover gasket rail. B . Observe dial indicator movement while moving valve from side to side (crosswise to the head). The dial indicator measurement must be taken just above the valve guide bore. C . Drop the valve head about 1.6 mm (0.063 in.) off the valve seat.
Figure 12-52 Measuring Stem-to-Bore Clearance (Typical) G643 (E) Service Manual Chapter 3. Engine Mechanical System 87