Operator`s manual
Figure
6-9
Diagram
of
Hydraulic
Tappet
6-26.
CYLINDER
HEAD
(VISUAL
INSPECTION).
Ex-
amine
the
cylinder
head
thoroughly,
checking
for
the
following
possible
defects.
a. Loose,
scored,
pitted
or
otherwise
damaged
valve
seats.
(Mark for
replacement.
)
b.
Loose
or
damaged
studs.
(Replace
with
0.003,
0. 007
or
0. 012
oversize
studs).
c.
Loose
or
damaged
spark
plug
heli-coil
inserts.
(Mark
for
replacement
with
oversize
insert.
)
d.
Loose,
cracked
or
scored
valve
guides.
(Mark
for
replacement.
)
e.
Nicked,
scored
or
dented
mountingpads.
(Intake
and
exhaust
ports,
rocker
box
covers.
)
f. Cooling
fins.
The
following
standards
shall
pre-
vail
insofar
as
acceptance
or
rejection
of
cylinder
heads
are concerned.
1.
Cracked
fins.
(a)
Fin
adjacent
to
the
exhaust
port
flange.
(1)
Stop
drilling,
a
3/16
inch
diameter
hole
through
the
end
of
the
crack
is permissible
providing
the
end
of
the
crack
is at
least
1/4
inch
from
the
base
of
the
metal.
(2)
Fin removal
to eliminate
crack
and
re-
duce
vibrating
mass
is permitted
provided:
aa.
Maximum
removal
is
no
more
than
one
half
the total
fin
width.
bb.
Maximum
removal
is
in
accordance
with figure
6-10.
cc.
No
burrs
or
sharp
edges
are
per-
mitted.
Section
6
Cylinders,
Pistons,
and
Valve
Train
OVERHAUL
MANUAL
LYCOMING
DIRECT
DRIVE
AIRCRAFT
ENGINES
1.
Shroud
Tube
7.
Camshaft
2.
Push
rod
socket
8.
Tappet
body
3.
Plunger
spring
9.
Cylinder
4.
Oil
pressure
chamber
10.
Ball
check
valve
5.
Oil
hole
11.
Plunger
6.
Oil
supply
chamber
12.
Push
rod
dd.
Minimum
fillet
at
the
root
of the
re-
moved
portion
of
the
fin
is
one
quarter
inch
radius.
Minimum
corner
at
top
of
fin
adjacent
to
the
removed
portion
is
one
half
inch
radius.
(b)
Fins
other
thanthe
above
may
be
accepted
provided
not
more
than
one
crack
per
fin
and
its
depth
is
no
closer
than
1/4
inch
from
the
base
of
the
metal
and
a
fin
stabilizer
is
used
to
reduce
vibration
and
further
deepening
of
the
crack.
2.
Physically
damaged,
broken
or
bent
fins.
(a)
The
blended
area
for
any
one
fin
shall
not
exceed
3/8
square
inches,
nor
3/8
inch
in
depth.
(b)
No
more
thantwoblended
areas
on
anyone
fin.
(c)
No
more
thanfourblendedfins
on
thepush
rod
side
of
the
head.
No
more
than
sixblended
fins
on
the
anti-push
rod
side
of
the
head.
(d)
Inadditionto
the
above,
it is
recommended
that
a
fluorescent
penetrant
inspection
of the
cylinder
be
made.
Pay
particular
attention
to
the
following
areas.
(1)
Between
the
15th
and
20th
cylinder
fin
(counting
from
the
top)
on
exhaust
port
side
of cylinder.
(2)
The
area
around
the
lower
spark
plug
counterbore.
6-27.
CYLINDER
HEAD
(DIMENSIONAL
INSPEC-
TION).
Check
the
ID
of each
intake
valve
guide
(it
is
recommended
that
exhaust
valve
guides
be
replaced
at
overhaul)
with
the
flat
plug
rejection
gage
(ST-81).
Check
the
diameter
and
out-of-roundness
of
the
guide
bore
by
checking
with
the
gage
at
a
minimum
of
two
positions
90
apart.
If the
gage
enters
the
guide
at
any
of
the
positions
tested,
markthe
guide
for
replacement.
Check
the
ID
of
the
rocker
shaft
bushings
in
the
cyl-
inder
head,
using
the
flat
plug
rejection
gage
(64613).
Be
sure
to use
the
end
of
the
gage
marked
"Cyl.
Head".
The
opposite
end,
marked
"Rocker
Bushing"
is
0. 0015
inch
larger
in diameter
by
virtue
of the
greater
wear
limit
allowed
on
the
valve
rocker
bushing.
As
in
the
case
of the
valve
guides,
check
for
out-of-roundness
by
trying
the
gage
at
several
different
points
on each
diameter
being
checked.
-MAX.
FIN
REMOVAL
TO THIS
LINE
ONLY.
NEVER
ENTER-
BASE
METAL.
Figure
6-10.
Maximum
Fin
Removal
6-8