Chapter 3 Engine Classifi cation, Parts Identifi cation 53
illustrates the use of a rocker arm and push rod setup
to actuate the valves. The rocker arm is mounted on
a rocker shaft. Note how push rod force is trans-
ferred in the opposite direction by the rocker arm.
Figure 3-9 illustrates the use of a rocker arm and
push rod valve train on an actual engine. Figure 3-10
shows a different rocker arm design. Instead of oscil-
lating on a rocker arm shaft, this type uses a ball
pivot arrangement on which the rocker arm pivots.
Valve
Rocker arm
Camshaft
Cam lobe
Figure 3-7.
Transverse cross-section of an I-head (overhead valve)
engine. Both intake and exhaust valves are located in the
head.
Dodge
Rocker arm
Valve
Camshaft
Lifter
Cam lobe
Push rod
Rocker shaft
Figure 3-8.
Schematic shows simplifi ed valve train for one cylinder of
an overhead valve engine.
Goodheart-Willcox Publisher
Push rod
Rocker arm
Valve
spring
Valves
Hydraulic
roller lifter
Camshaft
Figure 3-9.
Cutaway view shows a typical valve train used to operate
overhead valves on a V-6 engine.
Dodge
Rocker arm
Rocker arm
ball pivot
Push rod
Lifter
Camshaft
base circle
Valve
spring
Valve
Figure 3-10.
Ball type rocker arm. Note the shape of the ball pivot.
TRW, Inc.