Paragraphs 76-80
shaft is .002-003. If clearance exceeds
.008,
renew the rocker arm and bush-
ing unit and/or shaft. Early produc-
tion engines were equipped with
forged rocker arms which have been
discontinued and replaced by built-up,
stamped steel type on all models.
Rocker arm bushings are not available
separately except for the discontinued
forged type rocker arms.
The inlet valve rocker arm can be
identified by a milled notch located on
its upper surface between shaft and
valve stem end. Reinstall rocker arm
shafts with the oiling holes toward
the cylinder head.
On B, C, CA, and RC, the grooved
support stud shown in Fig. AC29
should be installed in rear stud hole.
This stud acts as an oil passage to
lubricate rocker shaft.
On all models be sure to install
copper or composition washers be-
tween cover and cover nuts to insulate
noise.
VALVE TIMING
All Except Model
G
76.
Valves are correctly timed when
marked tooth of crankshaft gear is
meshed with the correct mark on
camshaft gear. If camshaft gear has
two identical marks, the one opposite
the keyway should be meshed with
marked tooth of crankshaft gear, and
the opposite one with the mark on the
magneto gear. All "CE" engines and
"BE"
engines numbered BE12550 and
higher have camshaft gear marked
with a straight line and an "O" or a
dot. On these engines, mesh the
straight line of the camshaft gear with
the similarly marked tooth on the
ALLIS-CHALMERS
Fig, AC29~Models
B, C,
CA,
and
RC rocker
arms, kocker shaft rear support stud
is
grooved
to
provide
oil
passage
to
rocker
arms.
Fig, AC30
-
Timing gear
marks
on all "d"
engines
and
"BE"
engines
num-
bered BiJ25S0
and up. On
"BE" engines prior
to
BB-
12550,
the
camshaft gear
has
two
identical marks;
the
one
opposite
the key-
way should
be
meshed
with
the
crankshaft
gear.
crankshaft gear and the "O" mark
with the **O" mark on the magneto
gear. Refer to Fig. AC30.
Number one cylinder inlet valve
opens at top center and exhaust valve
closes 10 degrees after top center.
To check valve timing when engine
is assembled, adjust number 1 inlet
valve clearance to .014. Insert a .004
feeler gage between rocker arm and
valve stem and rotate crankshaft until
a slight drag is felt while trying to
withdraw the feeler gage. At this time,
the top center mark on fiywheel should
be in register with, or not more than
V4 inch either way from center of in-
spection port. Reset tappet gap to
proper clearance. On flywheels which
do not have a top center mark, the
top center point can be established by
measuring back from the "Fire" or
"F"
mark or by using the starter ring
gear teeth as a basis for calculation.
On the WD, which has a ring gear of
100 teeth, TC would be 8 1/3 teeth
(3yg" on rim) after the "Fire" mark,
as shown in Fig. AC46.
Model
G
77.
To check timing when engine
is assembled, adjust both tappets of
No.
4 cylinder to .020, then crank en-
gine until No. 4 piston is at top center
on the exhaust stroke. This point is
indicated when the notch on crank-
shaft pulley is Vs inch past the center
of the inspection port, located in the
hood support as shown in Fig. ACS3G.
If valves are correctly timed, both
valves will now be closed and it should
be possible to rotate both tappetb
with the fingers.
TIMING GEAR COVER
Models B-C-CA
78.
To remove cover, remove tractor
hood and support tractor under torque
tube.
Remove radiator and axle or
pedestal and front support as a single
unit. Disconnect governor controls,
and remove governor control housing.
Remove crankshaft pulley, fan blades.
and fan belt. On some engines, the
front-center oil pan retaining stud is
welded to the angle iron on timing
gear cover, necessitating removal of
the oil pan assembly. Where the sfud
is not welded, cover can be renewed
without removing the oil pan, but as
a protection against subsequent oil
leaks,
it is advisable to always remove
the oil pan. If oil pan is not removed,
the oil pan gasket must be very care-
fully separated from the timing gear
cover. Screws of three different
lengths are used to retain the cover;
be sure they are installed in the cor-
rect locations.
Model
G
79.
Although it is possible to renew
crankshaft front oil seal without
removing the timing gear cover, our
suggestion is to remove the cover,
which entails little additional work.
To remove the timing gear cover, re-
move the hood, hood support and
crank jaw. Disconnect carburetor link
rod and governor spring. Remove
pulley, using a puller and two % inch
cap screw§ to attach same. Do not
thread screws too far into pulley, as
they may damage the cast timing gear
cover. Remove the cover to cylinder
block cap screws and withdraw the
cover.
The seal which consists of an outer
felt washer and an inner fianged ring
of treated leather, should be installed
with the lip of the inner element fac-
ing the timing gears.
Models RC-WC-WD-WD45-WF
80.
It is possible to renew crank-
shaft front oil seal without removing
the timing gear cover. The oil seal can
be renewed after removing the hood,
radiator, crankshaft pulley and front
seal retainer. Loosen timing gear cover
retaining cap screws to facilitate cen-
tering oil seal. Latest seals are of felt
faced with neoprene.
16
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