Operator`s manual

OVERHAUL MANUAL- LYCOMING DIRECT DRIVE AIRCRAFT ENGINES
Section 6
Cylinders, Pistons,
and Valve Train
SECTION 6.
CYLINDERS,
PISTONS
AND
VALVE TRAIN
6-1.
The piston, being a
reciprocating part, is
nor-
mally grouped with the crankshaft in a theoretical
breakdown of the engine into basic components. How-
ever, from a practical standpoint, it is felt that the
piston should be considered with the cylinder insofar
as overhaul procedures are concerned. For example,
the basic configuration of the engine requires the re-
moval and reassembly of the pistons at the same time
the cylinders are removed or replaced.
6-2. For
the purposes of this
manual, the valve train
will be considered as
all parts of the valve
operating
mechanism
beyond the camshaft,
beginning with
the
hydraulic tappet assembly.
6-6. INTERCYLINDER
BAFFLES.
(Where applicable)
Using the intercylinder
baffle tool
(64885), turn the
baffle
retaining hook
so that it
disengages
the retainer.
Remove
the intercylinder baffle
and hook from between
the cylinders.
6-7. OILDRAINTUBES. Loosen hoseclamps at lower
end of
tube and slide tube out
of hose. Loosen gland
nut at cylinder head fitting and remove drain tube.
6-8. Deleted
6-9. Deleted
6-3. Although subject
engines employ either
parallel
valve cylinders
or angle valve cylinders
with either up
exhaust or down
exhaust, basic overhaul
procedures
are the same
for all cylinders. The
overhaul proce-
dures
described in this
section will be applicable
to
all cylinder assemblies except as noted.
6-4. Either plain
steel, chrome plated,
or nitride
hardened steel cylinders may be employed on the en-
gines discussed
in this overhaul
manual. The color
code for these cylinders is as follows:
a. Plain steel
b. Chrome plated
All grey
Orange paint
on cylinder
fins below spark plug
hole.
6-10.
CYLINDER ASSEMBLY
(All models) Remove
rocker box covers
and gaskets. Rotate
the crankshaft
to place the piston of
No. 1 cylinder at top
center of
the
compression stroke.
(With the piston inthis
posi-
tion both valves
will be closed and the
piston exgended
away from
the crankcase to
avoid damage when the
cylinder is removed. )
6-11.
PARALLEL VALVE
CYLINDERS (Except-
0-235, O-290-D, -D2)
See figure 6-1. Remove
the
valve
rocker shaft (8) and
remove valve rockers
(5)
and valve stem cap from exhaust valve stem. Remove
the push
rod by grasping the end
and pulling through the
shroud tube
(1). Remove the plain
nut (4) lockplate (3)
spring (2) and spacer. Pull the shroud tube (1) through
the cylinder
head and discard
the shroud tube seals.
6-12.
(0-235, O-290-D,
-D2). See figure 6-3.
Re-
move valve adjusting
nuts (19) and screws
(18). Note
that the shroud tubes
on these models cannot
be re-
moved until
the cylinder is removed.
Remove the valve
rocker
shafts (14) and valve
rockers (13 or 17).
Re-
move the push rods (12) from the shroud tubes.
c. Nitride hardened
Blue paint on cylinder
fins
steel
below spark plug
hole.
d. . 010inchoversize
plain cylinders
Green when applied to
customer overhaul en-
gines.
e. . 020inchoversize
plain cylinders
Yellow
when
applied to
customer overhaul en-
gines.
NOTE
A yellow color, on fins ABOVE sparkplug
hole,
indicates that longreach
sparkplugs
are used.
REMOVAL FROM ENGINE
6-5. It
is assumed that the
ignition harness, intake
pipes and primer or fuel injection lines have been pre-
viously removed.
6-13.
ANGLE VALVE CYLINDERS.
See figure
6-5 or
6-6. Remove rocker shaft covers (31) and gaskets.
Pushvalve
rockers shafts
(20) outward to allow
clear-
ance for removal
of valve rockers (22) andthrustwash-
ers (23). Remove valve stem cap (32). Do not attempt
to remove valve rocker shafts until the cylinder is re-
moved. Remove the push rods (13) by pulling through
the shroud tube (18). Using shroud tube wrench (ST- 142)
turn each shroud
tube 90
°
either
way, this releases
the detent on tube from spring. Remove the tubes by
first releasing
them from the
seal seats in cylinder
head and then withdrawing tubes from seal retainers in
crankcase.
Remove shroud
tube
seal sleeves
(19) and
seals
(14) from
end of shroud
tubes;
also remove
seals from
crankcase. Discard
all seals. Place washer
(15),
springs (17)
and sleeves
(19)in
the cleaningbas-
ket.
Revised May, 1972
6-1