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18
Chapter I-General Engine Repair
6269
fig. 17-Measuring O .D. of Valve Stem
If the valve face
funOut
exceeds
specifications,
grind
the
valve
face. If the run
cut
still
exceeds
specifications
after
grindin
g,
discard
the
valve.
Grind
a
ll
grooves or score marks
from
the
valve
stem
ends.
H
owever,
do
n
ot
remove more than 0.010-
inch from
the end
of
the stem.
(3)
REF
ACING VALVE
SEATS.
Grind the
valve
seat
with
a grinder
(fig. 22). Remove
only enough stock
to clean up pits
or
grooves
in the seat.
If
th
e va lve
seat
width
exceeds specifications
(figs.
23 or
24),
re-
move just
enough
stock
from the top
and
bottom
edge
of
the
seat
to reduce the width.
U
se a 30
0
angle whee
l
to remove
stock
from the
bottom of the seat and a
60°
angle
wheel to
remove stock
from the top.
K
eep
the seat as
near to the
center
of the valve
face as
possible.
After
refaeing va lves and seats, it
is
good practice
to lightly
lap
in
the valves
with
a
medium
grade
lapping compound,
to match the
seat and
the
va
lve.
(4) VALVE
SEA
T
INSE
RT REPLACEMENT.
To
remove
the exhaust
valve insert
from the 256,
279,
fig
.
18-Reaming Valve Guides
Gauge
~
__
puot fa, Rema,ing and
Installing
Gauge
fig
.
19-Valve Seat Runout Check
6270
a
nd
the
3
17
cubic
inch
engi nes,
invert the
h
ead a
nd
in-
sert a drift through the exhaust valve
port, then drive
the seat out.
Counter bore the insert recess to
specifications in
the
manner
shown in
fig.
25.
Cut
slightly (0.00 1-0.002 inch)
below
the
old
counterbore
depth
to
clean
up
this face.
Clean
out chips and a
ll
oil
from the
recess.
Chill
the oversize insert and t
h
e installation tool
in
dry
ice for
V2-hour.
Position
the insert on
the
tool
with
the
small
radius on
the outer edge
facing
outward.
Pilot
t he
driving
tool
in the
va
lve
guide,
then drive the in-
sert
into the
counterbore
until
it
is
fully
seated. Do
not peen the area around
the
insert.
R
eface
the new
valve seat insert.
CAUTION:
The
inslnllalion
of
Ihe
illSerl
musl be
perjorrned
irnrnelliately on
re
moval
oj
tlte
1
,001
and
insert
from
th
e dry ice. Protect
the
hands
with
gloves
when handlin
g
'h
e chilled
insert
and tool.
d.
Valve Lash Adjustment.
Valve lash
is
adjusted
by means of the
se
t
screw
and lock
nut located
on
the push rod
end
of the
rocker
arm.
If
the
cylinder
head or
the
rocker mechanism
has
been
removed and
installed, it will be
necessary
to
fig. 20-Measuring Valve Seat Width
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