Figure 3-56. Hydraulic Tappets.
in larger, low-speed engines. They almost. always pivot
tappet, valve-in-head engines is usually in the form of a
on a common shaft. Aluminum rocker arms generally are
screw on the rocker arm. On overhead valve (or push
used on small high-speed applications. On special
rod engines), there is usually a screw-type adjustment
applications, such as engines used in competition,
where the push rod actuates it. The adjusting screw can
aluminum rocker arms will be pivoted in needle bearings.
either be of the self-locking type, or have a jamnut to lock
it. A few engines are equipped with adjustments on an
d. Adjusting Clearance (Fig. 3-60). The provision for
adjustable mounting pivot. By turning the
Figure -3-57. Tappet-to-Cam Lobe Relationship.