BYPASS
VALVE
Located
on
the outside of the rear bearing plate, the
bypass valve (Figure
76)
controls
oil
pressure
by
allowingexcessoil toflow directly backtothecrank-
case. Normally the valve begins to open at about
25
psi
(172.5
kPa).
It
is
non-adjustable, and normally
needs no maintenance.
To
determine if high oil pressure is caused by the
plunger sticking closed, or
low
oil pressure by the
plunger sticking open, clean
and
inspect the valve.
To
remove the valve, unscrew the recessed plug
in
the rear bearing plate and lift out the spring and
plunger assembly. Determine proper valve operation
by checking thespring and plunger against thegiven
values:
Plunger Diameter
.
.
. .
.
Spring
0.3365
inch
to
0.3380
inch
(8.5471
to 8.5852
mrn)
2-5/16
inches,
+
1/16
inch
(74.613,
+
1.588 mm)
2.225
Ib.
at
1-3/16
inches (compressed)
(1.01
kg) at
(30.163
rnm)
(compressed)
Free Length
.
.
. .
. .
.
.
FIGURE
76.
BYPASS
VALVE
CYL. HEAD
CY
L.
HEAD
3
AND
4
lAND2
4
CY
LINDER
ONLY
W
FLUSH ROCKER BOXOIL LINE
WITH FUEL
AND
CLEAN HOLES
WITH
FINE
WIRE.
Pjee
Note
2)
OIL FILTER
ADAPTER
I
1
J
ECTlON
PUMP PAD
Note
1
-Usea#70drill bit (.028in. [1.17
mm])
for cleaning being careful not to
enlarge hole.
These
are restricted flow
fittings.
If holes are enlarged, valve deck
will receive excess oil. If
holes
are plug-
ged.valvetrain will rundryand wearout.
Note
2
-
Use a
#56
drill bit for cleaning
being careful not
to
enlarge hole.
It
is
critical that fittings be kept open.
If
restriction is plugged, injection pump
tappet, bottom, and plunger will wear
out.
FIGURE
77.
CLEANING
ROCKER BOX OIL LINE AND RESTRICTION ORIFICES
63
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