ALLIS-CHALMERS
longer than exhaust guides and extend
farther into the ports. Desired clear-
ance of the inlet and exhaust valve
stems in the guides is .002S-.0045.
Model G
71.
Inlet and exhaust guides are
interchangeable. They are presized,
but should be reamed after installation
to .316 which will remove any local-
ized high spots. Guides should be
pressed or driven into the block, using
a piloted drift .002 smaller than bore
of guide, until top of each guide is
25/32 inch below gasket surface of the
cylinder block. Desired clearance of
inlet valve stems in guides is .002—
of exhaust stems .0035. If inlet clear-
ance exceeds .005, or exhaust clear-
ance exceeds .007, renew the guides.
VALVE SPRINGS
72.
Model G, inlet and exhaust valve
springs are interchangeable. Each
spring should require 13-17 lbs. pres-
sure to compress it to a height of 1%
inches from its free length of 1 13/16
inches.
Spring can be removed without re-
moving head by screwing adjusting
screw down against lock and holding
valve up with wire through spark
plug hole.
On other models spring should
require 33-39 lbs. pressure to com-
Paragraphs 71-75
Fig.
AC2a-Models WC, WD, WD45 and WF cylinder head and rocker arm assembly
showing exhaust valve seat inserts. Inlet valve seat inserts are available for service,
1.
Retainer 4. Support 7. Oil tube
2.
Washer 5. Rocker arm 8. Rocker busbinir
3.
Support stud nut 6. Oil collar
press it to a height of 1% inches and
SS-65 lbs. at a height of 1 S/16 inches.
Springs which are rusted, distorted,
or do not meet the foregoing pressure
specifications should be renewed. On
overhead valve models, springs may
be renewed without removing the
cylinder head after removing the
rocker shaft.
CAM FOLLOWERS (Tappets)
All Except Model G
73.
Mushroom type tappets (cam
followers) operate directly in ma-
1.
Pin type lock
2.
Inlet valve
3. Valve suide
4.
Valve spring
6. Spring retainer
6. Tappet screw
7.
Lock nut
8. Valve tappet
9. Camshaft
10.
Thrust plate
11.
Cam gear
16.
Roto cap
18.
Split cone lock
Id. Exhaust valve
IS-
IS-^
Fig.
AC27-Model G camshaft, valves and tappets. Note governor vent (X) in camshaft
and items (16) and (IB) which are used only on the exhaust valves.
chined bores of the cylinder block.
Tappets are furnished only in standard
size and should have a clearance in
block bores of .OOOS to .002 with a
maximum allowable clearance of .007
for service. Any tappet can be re-
moved a^ter removing the oil pan,
rocker arms and shafts assembly, oil
pump, timing gear cover and cam-
shaft. Tappets should be adjusted to
.010 hot for B, C, and RC; .012 hot
for CA, WC, WD, WD4S and WF.
Model G
74.
Barrel type tappets (cam fol-
lowers) operate directly in the bores
machined in the cylinder block. Tap-
pets can be removed by first remov-
ing the valve spring which is accom-
plished by turning the adjusting screw
down against the lock and holding the
valve up with a wire through the
spark plug hole. Now remove the tap-
pet screw and lock element from the
tappet. Tappets should be adjusted
cold to .012 for both inlet and exhaust
valves. Tappets are furnished only in
standard size and should have .001
clearance in block bores.
VALVE ROCKER ARMS
All Except Model G
75.
Rocker arms and shafts unit
can be removed after removing the
hood, valve cover, oil line from cyl-
inder head to rocker arms and four
shaft support retaining nuts and wash-
ers.
To disassemble the rocker arms and
shafts assembly, remove hair pin type
retainer or cotter pin and washer from
ends of shaft. The valve contacting
surface of rocker arms can be refaced,
but the surface must be kept parallel
to rocker arm shaft and original radius
maintained. Desired clearance be-
tween a rocker arm bushing and a new
15
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