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Section 5-Rocker
Mechanism, Cylinder Heads,
Valves, Valve
lash Adjustment,
and Valve Timing
21
idling, check
the
valve
lash.
Adjust the lash,
if
necessary
(fig.
24). Install
the rocker
arm cover.
(2) 8-CYLINDER
ENGINES.
Remove
the
rocker
arm covers.
(a) PRELIMINARY
ADJUSTMENT.
Make
three
chalk
ma
rks
on the
crankshaft
damper.
Space
the marks
90
°
apart so
that
with
the timing
mark,
the damper is
divided
into
four equal p
arts (90
0
represents
1
/
4
tum
of the
crankshaft, or
1
/4
of the distance
around
the
damper
circumference).
R
otate the crankshaft
until number 1
piston is near
T.D.C.
at the end
of the compression
stroke.
Adj ust the
lash
on
the following
valves:
No.
I
-
E
xhaust
N
o.
I
-
Intake
No.4-
Exhaust
No.2-Intake
No.5-Exhaust
N
o.
7-
Intake
Rotate
the
crankshaft
180°
or
'/2
turn (this puts
number 4
piston
on
T.D.C.). Adjust the followin
g
valves:
No.6-
Exhaust
No.8-
Exhaust
No.4-Intake
No.
5-
Intake
Rotate
the
e ngine
270
°
or
3;'
turn
from
180
°
(this
puts
number
3
piston
on
T.D.C.)
and adjust
the follow-
ing valves:
No.
2- Exha
ust
No.
3-Intake
No.
3-Exhaust
No.
6-
Intake
No.
7-
Exhaust
No.
8-Intake
(b) FINAL ADJUSTMENT.
Run
the
engine
for
a
min-
imum
of 30
minutes at approximately 1200
T.p.m.
in
order
to stabilize
engine
temperatures.
With the
engine
idling,
check
the valve
lash.
Adjust the
lash,
if n
ecessary
(fig.
24).
Insta
ll
the
rocker
arm
covers.
e.
Valve
Timing.
V alve
timing
ch
~cks
should be made
when poor en-
gine
performance
is
noted,
and all
oth
er checks, such
as
carburetion,
ignition
timing,
etc.
fail to
correct
the
trouble. The followin
g
procedure
can be used to deter-
mine if
the
valve tim ing is correct with the engine
installed
in the
car.
The
procedure
ch
ecks
the
cam
timing
by using the
opening side
of
number
1 intake cam
lobe. At this point
1
0
of crankshaft
rotation
is equal
to
a pproximately
0.004
inch
change
in
ca
m
lift.
Remove
the
rocke
r
ann
cover
on
the 6-cylinder
en-
gine.
On
8-cylinder
engines, remove
the
right
rocker
arm
cover.
BE SURE
TO PLACE
INDICATOR
TIP
IN
CENTER
OF
PUSH
ROD
CUP
fig. 25-Camshalt
Lobe
Lift
Check-Typical
6607
Back
off the
number
1
intake
valve
adjusting
screw,
then
slide
the rock..!r
arm assembly
to
one side
and
secure it in
this position. Make
sure the
push rod is
in the
tappet socket,
then install a dial
indicator
in
such a manner as to
have the
actuating
arm
of the
indicator
in
the push rod
socket and
in the same plane
as the
push rod
movement
(fig. 25). Turn the
engine
slowly
(at either the crankshaft
dampe
r bolt
or
fly-
wheel)
until the tappet
is
on the heel
of
the
cam
lobe.
Zero the
dial
indicator, and
continue
turning the
engine
slowly
until the
desired
lift is obtained (Table 3). Com-
pare
the degrees on the pulley with
specifications.
If the valve
timing is not
within specifications, check
for
a
bent timing pointer. Bring the number 1
piston
to
T.D.C. and
see if the timing pointer is
aligned with
the
T.D.C.
mark
on the crankshaft pulley
or'
damper.
If
the
pointer
is not
at fault,
check the
timing chain (or
timing
gears), camshaft
sprocket,
crankshaft sprocket, camshaft,
and crankshaft
damper,
in
the
order of
accessibility.
Table 3-Valve Tim;ng Specifications
Intake Tappet Lift
(Opens)
Engine
At Crankshaft D egrees
(B.T.D.C.)
223
24°
BTDC
@
0.016 Cam Lift
272
12
°
BTDC
@ 0.016
Cam
Lift
302
18°
BTDC
@
0.010 Cam Lift
332
18°
BTDC
@
0.010 Cam Lift
6. TIMING
CHAIN AND SPROCKETS, TIMING GEARS, AND CAMSHAFf
a. Timing
Chain and
Sprockets.
To measure
timing
ch
ain
deflection
(fig. 26), take
up
t he slack
on
the
left side (as viewed from the front)
of the
chain
by rotating the
crankshaft
in
a
clockwise
direction. Establish
a
reference point
on
the block and
measure from this point to the chain: Rotate the
crank-
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