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1-78
FIG. 8
-Crankcase
Ventilation
by-pass.
When
the
clement
is
dirty
and
will
not permit a sufficient How
of
oil,
the pressure
acting
on the
inner
face
of
the valve
drops.
If
tbe
pres-
sure
difference
between
the
valve
faces
is great enough to overcome
spring
pressure,
the valve
will
open.
Oil then
by-passes
the element,
main-
taining an emergency
supply
of
oil
to
the engine.
The
oil from
the
filter
flows
through
a passage in
the
block
to
the
oil
cooler
located
in
the
water
passage
al
the
front
of the
block
adjacent to
the
No.
t
cylinder.
A
spring loaded relief
valve
in
the oil
cooler cover opens at
approximately
15
psi
pressure dif-
ferential.
In
the event of
any obstruc-
lion
andl
or
malfunction
of
the
oil
cooler,
the engine
oil
will
by-pass the
oil
cooler,
maintaining adequate
en-
gine
lubrication.
From
the
oil
cooler,
the
oil flows
into
the main oil
gallery
located
in
the
center
of
the
valve chamber
Hoor.
The
oil gallery supplies
oil to
each
camshaft
bearing through drilled pas-
sages in
the
block.
Passages
are
drilled
fro
m each
camshaft
bearing
to
each
main bearing.
Number I camshaft
bearing feeds No.
I main
bearing.
and No. 2
camsha
h
bearing
feeds
No.
2
main
bearing,
etc.
The
oil
then
flows
through
notches o
r
grooves
in
the
main
bearings
to lubricate
the
crankshaft
journals.
The
crankshaft
is
drilled from the
main
bcarings to the
connecting
rod
bearings.
The
oil
flow
is
as
follows:
GROUP 1-
ENGINES
FIG.
9
-Wate
r
Pump
Main Bearing
No.
I
Serves
No.2
Serves
No.3
Serves
No.4
Serves
No.5
Serves
Conneeting
Rod Bearing
No
.
I
Nos.
2
and
5
Nos.
3
and
6
Nos.
4
and
7
No.8
A
small groove
is located
in
the
connecting
rod at
the
mating
face
where the
cap contacts
the
connect.
ing rod. This
groove
is
used
as an
oil
squirt
hole
for
cylinder
wall
lubrica-
tion. Oil
from
the
connecting
rod
squirt hole
lubricates
the opposite
cylinder
wall.
For example,
the No.
I
connecting
rod lubricates No.
5
cylinder
wall,
etc. As
the
cranks haft
turns, the
hole
in
the
connecting
rod
bearing
aligns
with
the hole
in
the
journal
causing a
direct
squirt
of
oil
onto the
cylinder
wall
.
A
passage
is
drilled
from
the
No.
I
camshaft bearing to lubricate
the
air
brake
compressor.
Oil
fro
m the
com-
pressor
is
returned
directl
y
to the
oil
pan
through
a
return
hole
in
the
side
of
the
block. The No.
I
camshaft
bearing also
lubricates
the
timing
gears.
A
passage
is
drilled
from the
No.
2 camshaft bearing
web to
the
No.
2
valve
rocker
shaft
support
to
lubri-
cate
the righ
t
valve rocker
ar
m shaft
assembly.
The
left
valve rocker
arm
shaft
assembly is
similarly lubricated
from the
No.4 camshaft
bearing
web
and
the
No.4 rocker ar
m
shaft
sup-
port. The
o
il
enters the valve
rocker
arms
through
the
valve
rocker ar
m
shaft
supports.
The
oil
from
the
sup-
porlS
flows
through
drilled
holes
in
each
roc
ker
arm
to
lubricate each
rocke
r
ar
m
bushing
and
the
valve and
ball
joint
ends
of
the rocker
arm.
The
excess oil
spirals
down
the rotat-
ing
push
rods
and
assists
in
lubricat-
ing
the tappets
and push
rods.
A
bame
located under
the
valve rocke
r
shaft assembly
shields
the valve
ste
ms
from
oil
splash.
The
governor, located
at
the
rear
center section
of the
engine,
is
lubri-
cated
from
the rear
of the
main
oil
gaUery.
The oil
pressure
sending
unit
and
the
tachometer
drive are
at-
tached
1
0
the
governor.
The
distri
butor
drive
is
lubricated
fro
m
a drilled passage
from the
No.1
camshaft bearing
web.
CRANKCASE VENTILAnON
A
crankcase
ventilation
tube
is
located
at
the
rear
oC
the
engine.
The
forward
motion
of
the
truck causes
a
partial
vacuum to be formed at the
tube.
This
vacuum action
causes
air
to
be draw
n
through
the
engine from
the
ventilation fi
lter
located
on
each
valve rocker arm
cover
(Fig.
8).
The
filter
contains
a
replaceable pa-
per
element
which
filters
the incom-
ing
air.
COOLING SYSTEM
The cooling
system
has three
stages
of operation.
A
thermostat
is
located
at the
rear
and at
the front
of
tr
intake
manifold.
The rear
thermost
(which
opens
first) allows
coolan.
from
the
cylinder block to
pass
th
rough
the
intake manifold
and into
the
water pump for re-circulation.
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