Figure 3-47. Exhaust Valve Configurations.

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Section III. 3-12. Valves and Seats.

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TM-9-8000 Principles of Automotive Vehicles Manual

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Figure 3-49. Valve Guides.

TM 9-8000

Integrally with the head, or they may be removable.

Removable valve guides usually are press fit into the

head.

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

REMOVABLE VALVE SEAT

valve seat. Valve guides may be cast

REMOVABLE VALVE SEAT

VALVE TO VALVE SEAT RELATIONSHIP

Figure 3-48. Valve Seats

3-28