Operator`s manual

valvesthrough
pushrods andvalve
rockers.
Thevalve
rockers are supported
on full floating steel shafts.
The
valve
springs bear
against
hardened steel
seats
and
are
retained
on the valve
stems by means
of split
keys.
A rotator
cap
is employed
on sodium
cooled
exhaust
valves.
NOTE
Hydraulic tappets,
which automatically
keep the valve clearance
at zero,
are used
on all
subject
engines
except the
0-235-C
and O-290-D
series
engines.
These
series
employ solid tappets
and the proper
valve
clearance is obtainedwith
the aid
of an ad-
justing
screw located
in the valve rocker.
SPLASH OIL TO ROCKER
ARMS,VALVE
STEMS,ETC.
DRAIN OIL TO SUMP
THRU OIL DRAIN TUBES
Section 2
General
Description
OVERHAUL
MANUAL-
LYCOMING DIRECT
DRIVE AIRCRAFT
ENGINES
2-7. HYDRAULIC
TAPPETS.
When the valve
is closed,
the face
of the cam
follower
is on the
base circle
or
back
of the cam.
The light
plunger
spring lifts
the hy-
draulic plunger
so that
its outer
end contacts
the push
rod, exerting a light
pressure against it,
thus elim-
inating any
clearance in the valve
linkage. As the
Figure
2-2.
Hydraulic
Tappet
Assembly
plunger
moves
outward,
the
ball
checkvalve
moves
off
its
seat.
Oil from
the
supply
chamber,
which
is di-
rectly
connected
to
the engine
lubrication
system,
flows
in
and fills
the
pressure
chamber.
As the
camshaft
rotates,
the cam
pushes
the cam
follower
and
the hy-
- GRAVITY
OIL THRU
SHROUD TUBES
TAPPETS
LEFT BANK
CRANKCASE OIL HEADER-LEFT
PRESSURE
OIL RELIEF
VALVE
DRAIN
OIL TO
SUMP
OIL SUMP
Figure 2-3.
Lubrication
Diagram
- 4 Cylinder
Engines
2-2
Revised
January,
1970