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16
Chapter
I-
G eneral
Eng ine
Repa ir
Fi
g
.
9-Pus
h
Rod
Runouf
Ch
eck
ing
them.
(val-ve
close
d) lind
obser-
v ing
the
Tunau!
.
If any
r
Ullout is
o
b
se
r'ved,
be
Sl.l.r
e
1
.0
check
I.h
e
rod
between
cen
te rs as described above.
(2)REPA
I
RS.
If
the
clearance
between the
shaft
and rocker arms
exceeds
O.004-inch,
replace
the shaft
and
/
or the rocker
arms.
Replace
all
rocker
arms
that
have severely
scored
or scuffed bores and
/
or grooved
pads.
R
eplace
all
severely
scored
or scuffed
rocker
shafts.
Dress
up
minor
nicks
or
scratches.
Repl
ace
all
damaged
rocker afm
lock nuts,
adjusting screws,
and
springs.
Repl
ace
the oil drain tube if it is
cracked or has
a
sharp bend.
If
the total
runout
of
a
push
rod
exceeds
0.020
inch,
at
any
point,
discard
the rod.
Do not
attempt to
straighten push
rods.
h.
Cylinder
Head.
(1) CLEANING
AND
INSP
ECTION
.
Remove
the
cylinder head.
Remove
carbon
deposits
from the
com-
bustion
chamber and valve heads with a
scraper
and
a wire
brush.
Be
careful
not
to scratch the gasket
sur-
face.
Clean
the
gasket
surface
with
solve
nt to
remove
any gasket sealer.
Check
the
head for
cracks.
Check
the
gasket
sur-
faces
for fi atness
(fig.
10). Check
to
see
that
all
water
passages are
open.
Make sure
the
gasket surfaces
of
both
head
and
block
are
free from burrs
or
scratches.
Check
the
intake
port mating surfaces
for
flatness as
shown in fi
g. 11.
Check
the
cylinder head
core
plug for
evidence
of
leakage.
)!li)
CH":K
DIAGONALLY
CHECK
ACROSS
CENTER
6262
Fig
.
IO-Ch ecking
Flafn
ess
of fh
e
Cylind er Head
Ga sket
Surface
6264
Fig.
I I-Ch
ec
king
Flafn
ess
of fh
e
Infak
e
Porf
Mating
Surfaces
(2)
REPA
IRS
.
R
emove a
ll
burrs or
scratches
with
an
oil stone. Rep
lace
the head
if
it is
cracked.
If
the
cy
linder
head
core plug
leaks,
replace
it
as
indicated
for
the
particular engine.
c. Valve
Mech
a
nism.
The
two
types of valve assemblies used
in the
truck
engines
are
the rotating-type
(fig. 12) and the free-
turning-type
(fig.
13
).
Table
1
lists the
valve types
peculiar
to each engine.
Those
engines
incorporating
umbrella-type va lve
stem
seals are also designated in
T
ab le
1.
Valve
guides are made
integra
l
with the
cylinder
heads.
Valves
with oversized
stems
are
available
as
replacements if
it
becomes necessary
to ream
the
valve
guides.
(1) CLEANING AND INSPECT ION.
Before remov-
ing
the
valve assemblies from the cylinder
heads,
per-
form
a
cylinder
head
leak test
to
determine
if the
valves
are
seating properly. Turn
the cylinder
head
on
its
side and
pour solvent
into
the
ports.
If the
solvent
leaks past
the
valve seats,
the
valves are
not seating
properly.
Disassemble the
cylinder
head.
Discard umbrella-type
va lve
stem
seals, and
rep lace
wi~h
new
seals.
Scrape
and
/
or wire
brush
carbon
from
the
head
and stem of
the
valves.
Remove
varnish
from the
valve stems.
Care-
fully clean
all
carbon from the
va lve seat with a wire
brush.
Table I-Valve
Parfs
Peculia
r
fo
Ea ch Eng
i
n
e
Engine
Umbrel
la
Rotating
Free Turning
Seals
V
alves
Valves
(
Cubic
Inch)
Int.
Exh.
Int.
E xh.
Exh.
223
Yes
Yes
Yes
Yes
239
Yes
Yes
Yes
Yes
256
Yes
Yes
Yes
279
Yes
Yes
Yes
317
Yes
Yes
Yes
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