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TM 9-8000
Integrally with the head, or they may be removable.
Removable valve guides usually are press fit into the
e. Valve Springs, Retainers, and Seals
(Fig. 3-50). The valve assembly is completed
by the spring, retainer, and seal. Before the spring and
the retainer fit into place, a seal is placed over the valve
stem. The seal acts like an umbrella to keep the valve
operating mechanism oil from running down the valve
stem and into the combustion chamber. The spring,
which keeps the valve in a normally closed position, is
held in place by the retainer. The retainer locks onto the
valve stem with two wedged-shaped parts that are called
valve keepers.
f.  Valve  Rotators.  It  Is  common  in  heavy-duty
applications to use mechanisms that make the exhaust
Figure 3-47. Exhaust Valve Configurations.
valves rotate. The purpose is to keep carbon from
building up between the valve face and seat, which could
sucked into the combustion chamber past the intake
hold the valve partially open, causing it to burn. The
valve stem during the intake stroke.
release-type rotator (A, fig. 3-51) releases the spring
(2) It keeps exhaust gases from getting into the
tension from the valve while open. The valve then will
crankcase area past the exhaust valve stems during
rotate from engine vibration. The positive rotator (B, fig.
the exhaust stroke.
3-51) is a two-piece valve retainer with a
(3) It keeps the valve face in perfect alignment with the
valve seat. Valve guides may be cast
Figure 3-48. Valve Seats


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