5-3
SECTION 5: CYLINDER HEAD AND VALVES
INSPECT AND REPAIR
1. Check cylinder head (Figure 5-7). Be sure all gasket mate-
rial is removed from surfaces before checking. Use a gasket
scraper if necessary.
a. Inspect cylinder head for cracks or damage.
b. Use a surface plate or straightedge and check cylinder head
mounting surface for distortion.
If mounting surfaces are distorted more than 0.1 mm (.004"),
the cylinder head must be replaced.
Note: It is not recommended that cylinder head mount-
ing surfaces be resurfaced.
Figure 5-7. Check Cylinder Head Distortion
2. Clean the valve guides and measure their I.D. using a split
ball bore gauge (Figure 5-8).
a. Replace head if either valve guide measures 7.06 mm
(0.278 in.) or more.
Figure 5-8. Check valve guides
REF
ACE V
ALVES AND SEATS:
1. Valve seats may be reconditioned using a valve seat cutter.
If valve seat is wider than dimension shown in Figure 5-9, a
narrowing cutter should be used to ensure that contact area
of valve seat is centered on face of valve (Figure 5-10).
a. Use a 60° cutter to narrow seat from bottom and a 15°
cutter to narrow seat from top (Figure 5-9).
Note: If valve seat is loose or cracked, replace cylinder
head.
Figure 5-9. Valve Seat Dimensions
2. Valve faces may be resurfaced to 45°. See Figure 5-10 for
dimensions for valves.
3. Lap valves and seats with a valve lapping tool and valve
lapping compound.
Note: In most instances it is more economical to replace
the valves than to reface them.
Figure 5-10. Valve Dimensions
4. Measure valve stem diameter at specified distance from end
of valve, as shown in Figure 5-11.
Replace if less than 6.9 mm (0.272 inches), or if total clear-
ance between valve stem and valve guide exceeds 0.12 mm
(0.0047 in).
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