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Section 5-Rocker Mechanism
,
Cylinder Head,
Valves,
Valve
lash
Adiustment,
and
Valve
Timing
21
Back off
on
the No. 1
valve adjusting screw
and
push
the
rocke
r
arm to one side, then
install
a dial
indicator as
shown in fig.
28.
Zero
the dial indicator,
t hen
rotate
the
engine
slowly
until
the
desired
lift
is
obtained, as tabulated in
Table
2.
Compare
the
degrees
on the pulley to the
specifications.
If the
va lve
timing is not
within
specifications, make
sure the timing pointer has not been bent. This is done
by bringing No.
1
piston to T.D.C.
a
nd noticing if the
timin
g
pointer is in
alignment
with
the
T .D.C. mark
on the crankshaft pulley.
If
the
pointer
is not at fault,
it
will
be necessary to
check the
followin
g ite
ms in the
order of
accessibility:
timing
chain; camshaft sprocket;
crankshaft sprocket;
camshaft;
crankshaft
pulley;
and
crankshaft.
Engine
223
239
256
279
317
Table 2-Valve Timing Specifications
Camshaft
Intake
Tappet
Lift
( Opens)
A
t
Crankshaft
Degrees
(
B.T.D.C.
EBP-62s0-C
13
°
BTDC With
.013
Cam
Lift
ECE-62 sO-A
8
°
BTDC With .015 Cam
L
ift
ECE-62s0-A
8
0
BTDC With
.015
Cam
Lift
EAM-62s0-D
18
°
BTDC
With
.010
Cam Lift
EAM-62s0-D
18
°
BTDC
With
.010
Cam
Lift
6. CAMSHAFT
SPROCKET,
CAMSHAFT, AND CAMSHAFT BEARINGS
Procedures for the
inspection
a
nd rep
air
of
these
components are
conta
ined in the followin
g
paragraphs.
a. Camshaft Sprocket and Timing Chain.
Before the timing
chain
is removed, measure the
outward deflection from a
straight
line
of
the
slack side
of
the
chain (fig.
29).
If
the outward deflection
exceeds
V2 -inch,
replace the timing
chain.
(1)
INSPECTION.
Remove
the
camshaft sprocket
and
timing
chain.
Inspect the sprocket
for
broken,
chipped,
or worn teeth.
Chec
k the timing
chain
for
loose or worn
link
pins.
(2) REPAIRS.
Replace
a
sp rocket
that
has broken,
chipped, or worn teeth. Replace
a
timing
chain
that
has loose
or
worn link pins.
b. Camshaft and Camshaft Bearings.
The camshaft
must
be
repl aced when the lobes
a re
worn
to
such
an
extent
that
the cam
lobe
li
ft (intake
and
exhaust)
is
less
than
the
minimum
allowable
toler-
ance. Check cam lift with
a
dial
indica
tor
as shown
in
fig.
28.
It
wi
ll
be necessary to fabricate
a
clip to hold
the
push rod. The clip
shown
in
fig.
28 is made from
banding iron.
(1)
INSPECTION.
Before the camshaft
is
removed,
check the end play for conformance to
specifications
using a dial indicator in the following manner:
Push the
camshaft
toward the
rea
r of the engine.
Place a dial indicator against the front
side
of the
camshaft flange. Set the
dia
l
to
zero,
then pull the
camshaft
fo
rward.
Compare the dial indicator reading
with specifications.
Rem
ove
the camshaft. Thoroughly check the cam-
shaft for cracks with a magnifying
glass.
Examine the
lobes
for pitting, scoring, and
signs of ab normal wear.
Check
the lobes
with
a micrometer.
Suspected
worn
lobes
should
be compared
with
a
good
lobe
to be
sure
diagnosis is correct.
Measure
the journal for wear and
out-of-roundness. Measure
the
ca
mshaft front bearing
to journal
cleara
nce for conformance to
specifications.
Check
the
distributor drive
gear
for broken
or worn
teeth.
Chec
k
the
fuel pump
eccentric
for
wear.
(2)
REPAIRS.
R
eplace
a
ll
camshafts
that have
cracks or
seve
rely
sc
uffed
or scored
lobes.
Remove
light
scuffs or
scores
with a
hard Arkansas stone, then
polish
the
lobes
with
c
rocus cloth.
Rem
ove
raised
meta
l
from
sma
ll
nicks
and
abrasions
elsewhere
on the camshaft
in
the
same manner.
If
the front journal to bearing clearance is
excessive,
it
can be
assum
ed
that
a
ll
bearings
are
worn and need
replaceme
nt.
If
any of
the
teeth
on the distributor drive
gear
are
broken
or
worn,
it
will
be necessary to replace the
camshaft.
If the
end
play is
excessive,
replace the thrust plate
and
/
or spacer.
FIRST
TAKE
UP SLACK OF
POSITION
OF
CHAIN SHOWN
IN DOnED
OUnINE.
THEN,
TAKE
UP
SLACK ON
DRIVING SIDE OF
CHAIN
AND MEASURE SLACK
SIDE.
1781
Fig
.
29-Timing Chain Dellection Check
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