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1-88
GROUP 1- ENGINES
STEP 1-
SfT
NO.
I
PI
STON ON T.D.C., AT
END
Of
COMPRESSION
STRO
KE_
ADJUST NO.
I
,
.(
& S EXHAUST
AND
NO.
1,
2
I
I
FIG.
2a-Valve Lash Adjustment
STEP 3-
NO.
2,
3'-'
;
-;""-~-:::'
EXHAUST
AND
NO.3,
6
&
8
IN
TAKE VALVES.
1691.A
•
FIG. 27
-Preliminary Valve
lash
Adjustment
VALVE
LASH ADJUSTMENT
It
is very important
that
the valve
lash be
held
as close as
possible to
the
correct
specifications.
If
the lash
is
set
too close,
the valves
will open
too
early
and
close
too
late
resuhing
in rough engine
idle.
Burning
and
warping
of the valves
will
occur
also,
because
the valves
cannot
make
firm
contact
with
the seats long
enough to
cool
properly.
If
the
lash is
excessive,
it
will
cause
the valves to open
too
late
and
close
too early
causing valve
bounce.
In
additio n,
da mage
10 the
camshaft
lobe is likely
because the
tappet
foo
t
will
not
follow
the
pattern
of the camshaft lobe causing a
shock
contact
between these two
parts.
If
the
valve
rocker arm shaft aS4
sembly
has
been removed and
in4
stalled,
it will
be necessary to make a
preliminary
(cold) valve
lash
adjusl4
ment before
starting
the
engine.
If
the
adjustment is made
fo
r
an
engine
tu
ne-up,
follow
the
final adjustment
procedure.
The cylinders
are numbered
from
front
to
rear-
right
bank,
142 4 3 4
4
;
left bank, 5464748. The valves are
arranged
from front
to
rear on both
banks,
E4I4E4I·
I4E4I·E.
PRELIMINARY
ADJUSTMENT
The
cold
valve
lash
setting for
the
intake
valves
is
0.020 inch
and
0.022
inch
for
the
exhaust
valves.
Use a
step"type fee
ler
gauge
("go"
and
"
no
go") to adjust the
valves.
t
.
Make
th
ree
chalk
marks
on the
crankshaft damper
(Fig. 27). Space
the marks approximately 90
°
apatt
so
that with
the timing
mark,
the
damper is
divided
into
four
equal
parts
(90
0
represents
v..
of the
dis4
tance around
the
damper
circumfcr4
ence) .
2.
Rotate
the
crankshaft
until
No.
1 piston
is
near
T.O.C. at the
end of
the
compression
stro ke,
then adjust
the fo
llowing
valves:
No.
I-
Exhaust
No.
I
- Intake
No.4-
Exhaust
NO.2-
Intake
NO.5-
Exhaust
No.7-
Intake
3.
Rotate
the
crankshaft 180
0
,
or
VI.
turn
(this puts No.4
piston
on
T.O.C.)
,
then
adjust the
following
valves:
No.6-
Exhaust
No.4-
Intake
No.8-
Exhaust
No.5-Intake
4. Rotate
the crankshaft
270
0
,
or
¥.!
turn
fro
m
180
0
(this
puts
No.3
piston
on
T.O.C.),
then adjust
the
following valves:
No.2-
Exhaust
No. 3-Inlake
No.3-
Exhaust
NO.
6-Intake
NO.7-Exhaust
No.8-Intake
fiNAL
ADJUSTMENT
Before
a
final valve lash adjust-
ment is made, operate the engine for
a minimum of 30 minutes at approxi-
mately
1200 rpm
to stabilize
engine
temperatures. With
the
engine
id ling,
check the valve
lash
usi ng
a step-
type
feele
r
gauge only ("go"
and
"
no
go").
Adjust
the
intake
and
exhaust
valve
lash
(Fig. 28),
to
0.0
20
inch.
B
CRANKSHAFT DAMPER, CYLINDER FRONT COVER, AND TIMING
GEARS
CRANKSHAn DAMPER
IUMOYAl
1.
Drain the
cooling
system.
Re4
move
the
fan,
shroud,
and
radiator.
Remove
the
alternator,
air
compres-
sor,
and power
steering belts.
On
a
F4 or T-scries truck, lift tbe
front
of tbe engine approximately
one
inch with
a
Hoor
jack
to all
removal
of
the damper.
2. Remove the
damper
cap sere ..
and
washer.
Install the
removal tool
and remove
the
damper (Fig.
29).
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