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2-16
ENGINE DESCRIPTION
ENGINE
(38)
of each connecting rod, which registers with
the hole in crankshaft once in each revolution.
Piston pins are lubricated
by
splash.
The timing chain and sprockets are supplied
with oil through a small passage which
con-
nects the main oil gallery with a recess and
drilled hole in the camshaft thrust plate. The
hole
through the thrust plate is blocked by
the
camshaft sprocket hub except when a slot in
hub registers with the hole once in every revo-
lution of the camshaft, at which time oil is
thrown into the inside area of sprocket. Three
holes in the
camshaft
sprocket allow oil to pass
to the timing
chain.
See figure 2-11 or 2-13.
The rocker arms are supplied with oil by
pipes which
connect
the hollow rocker arm
shaft with the main oil gallery in
crankcase.
Oil is piped to a drilled passage in cylinder head
and a short pipe under the rocker arm cover
connects this passage to the top of
No.
1 rocker
arm shaft bracket. Holes in bracket and shaft
conduct oil into the shaft, which is closed at
both ends.
Figure
2-12-Secti onal
View
of Oil
Pipe
Connection to Oil Gallery
In
1948
engines having
adj ustable
valve lash,
a special connector extends into the main oil
gallery
so that oil is drawn from center of gal-
lery
where oil is clean. See figure 2-12. An ex-
ternal pipe jo
ins the connector with the
drilled
pas
sage
in
cyli
nder head. See figure
2-11.
The
special
connect or is
drilled
to a
size which con-
trols the volum
e of
oil
supplied to
the ro
cker
arm shaft.
On
1948
S
erie s 70
engines
equipped with hy-
draulic valve
lifters,
and
all
1949
engines,
the
outlet side of oil filter
is
conn
ected
to the drilled
passage in
cylinder head
so that
a
ll oil supplied
to val
ve
mechanism
passes t
hro ugh the filt
er.
See
figure
2-13.
The upper
pipe
fitting in cylin-
der head has a restricted opening to control the
volume of oil
supplied
to the rocker arm shaft.
Holes in the rocker arm shaft feed oil to each
rocker
arm
bearing.
A small hole in each rocker
arm feeds a slight amount of oil
t
o the contact
point between the arm and valve st em. A baffle
mounted above the
rocker
arms prevents oil
spraying from rocker arms
onto
the valve
stems in excess of the am
ount
required for
proper lubrication of valves and guides.
A passage drilled in each rocker arm con-
ducts oil to the ball stud. On engines having
adjustable valve
lash,
a small hole feeds oil into
the socket on push rod, from which the oil flows
down into the valve
lifter
to
drain
into
crank-
case through a
hole
in t
he
lifter. On engines
equipped with hydraulic valve
lifters,
the small
feed hole is not used; the pa
ssage
in ro
cker
arm
connects with a groove and hol
e
in
the
ball stud
through which oil is fed into the push rod. See
figure
2-10.
The push rod serves as a reservoir
to
maintain
a head of oil abo
ve
the
hydraulic
valve
lifter.
The ignition distributor
gears are gi
ven
posi-
tion lubrication by
mean s
of an oil passage in
the
crankcase running from
the
main
oil
gallery
to a point in the
distributor
housing f
rom
which oil flows over the
gears.
1948
engines having adj
us t able
valve
lash
are equipped with an
AC
oil filter containing
a cotton packed
element, No.
C-115.
The
inlet
side of filt
er
is connected
by a
pipe
to
the
No.
3 tapped port in
the
eng ine main oil
gallery.
On
Series 40-50 eng ine s,
the
filter
outlet
is
piped
to a tapped
hole
in the
crank
case.
On
Se
r ies 70
engines, the
outlet
is
piped
to a special dr illed
push rod cover
bolt through which the
filt
ered
oil r
eturns
to
crankcase.
19
4 8
S
er i e s 70 e
n g ines
eq
uip ped with
hydraulic
valve
lifters and
all
1949
engines are
equipped with an AC oil
filter
cont aining a
folded paper
low-restriction element,
No.
P-127.
•
The
inlet
side of filter is connected by a
pipe
to
t
he
No.3 tapped port in the engine
main
oil
gallery.
The filter outlet is piped
to the
drille d
passage in
cylinder
head
so that t
he valve
mechanism is
supplied
with
filtered oil. The
filter conta ins a valve which
will open at 7-9
pounds pressure t
o by-pass oil to the outlet in
case the filt
er
element becomes plugged or
otherwise
inoperative.
The
filter
elements
described above are
not
interchangeable.
Each filt
er bears a
label which
gives the number of the filter element that
must be used for replacement.
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