ALLIS-CHALMERS
Models WC-WD-WD45-WF
90.
Piston
and
connecting
rod as-
semblies are removed from above after
removing cylinder head
and oil pan.
Tighten
the
castellated connecting
rod nuts
to 70
ft,-lbs. torque
and
self-
locking
(lug
lock) nuts
to 40
ft.-lbs.
torque.
ALUMINUM PISTONS. Pistons
and
rods
are
installed with
the rod
corre-
lation marks facing
the
camshaft
and
the stamped arrow
on top of
each
piston facing front
of
engine.
The
*'T'*
slot
of
pistons should face opposite
to
camshaft side
of
engine. Replacement
rods
are not
marked
and
should
be
installed with piston
pin
clamp screw
facing
the
camshaft. Refer also
to Fig.
AC37.
IRON PISTONS. Piston
pin
bosses
are
of
unequal length. Pistons
1 and 3
have
the
long
pin
boss toward
the tim-
ing gears
and
Numbers
2 and 4
have
the long
pin
boss toward
the
flywheel.
Refer
to Fig.
AC38.
PISTONS, LINERS
AND
RINGS
Some
of
these engines
are
equipped
with iron pistons
and
some with alum-
inum,
alloy pistons. Both types
are
cam
ground.
Iron pistons are equipped
with
a
hushing
in
each
pin
boss; alum-
inum pistons are
not
hushed.
All Except Model
G
91.
Pistons are supplied
in
the stand-
ard size only
and
with variation
in
piston compression length
for
the three
compression ratios.
The recommended piston skirt clear-
ance
is
.002r)-.0045, with
a
maxi-
mum clearance
of ,010 for
service.
When assembling pistons
to
rods,
and rods
and
piston units
to
crank-
shaft,
do so as
outlined
in
paragraphs
88
and 90.
With
the
piston
and
connecting
rod
assembly removed from
the
cylinder
block,
use a
suitable puller
to
remove
the
wet
type liner (sleeve). Before
installing
a new
liner, clean
all
mating
and sealing surfaces.
The top of the
liner should extend .002-,004 above
the
top of the
cylinder block.
If
this
standout
is in
excess
of
,004, check
for
foreign material under liner flange.
Excessive standout will cause water
leakage
at
cylinder head gasket.
To
facilitate installation
of
liners,
use a
lubricant (palm
oil or
vaseline)
on
the
two
neoprene sealing rings.
Some pistons
are
three ring type,
and some
are
fltted with four rings.
Recommended
end gap of all
rings
is
.007-.017. Recoramended side clearance
is .001-.0025,
On four ring pistons,
the
scraper
type compression ring
is
installed
in
the third groove;
on
three ring pistons,
in
the
second groove, always with
the
scraper groove down.
Model
G
92.
Aluminum alloy pistons
are cam
ground,
and are
provided with
a ,002
to
.007
relief adjacent
to
both ends
of
the
piston
pin.
Repair pistons
are
available
in
standard
and in
oversizes
of .003S,
,020, and .040. The
recom-
mended
.002
skirt
to
cylinder clear-
ance,
is
measured with
a ^A
inch
feeler blade
of
.0015 thickness, which
should require
10 to 15 lbs.
pull
to
withdraw. Feeler should
be
inserted
between skirt
and
cylinder block
at
right angles
to the
piston pin, with pis-
ton
in
upside down position
as
shown
in Fig, AC39, Piston sizes
are
stamped
on
top of
each piston.
Cylinders
are
unsleeved
and
accord-
ing
to the
tractor manufacturer,
are
choke bored slightly (.0005) with
the
smaller diameter being near
the top.
Standard size rings
are
used
for
service until cylinders
are
rebored.
Rings
are
also furnished
in
oversizes
of
.020 and ,040.
However,
the
stan-
dard size rings used
in
factory produc-
tion
are not the
same
as the
standard
size rings provided
for
service,
as
will
be seen from
the
table below:
Production
Standard
Size
Compres- 2 tapered
sion Rings face, plain
Service
Standard
Size
Upper—chro-
mium plated.
Lower—ta-
pered face
with
an
ex-
pander
Fig,
AC36—Piston
and cylinder liner assem-
bly
as
used
in
early production
B and C
engines, and
all ftC
engines. Note iron
pis-
tons
are
equipped with piston
pin
bush-
ings. CA engines
are
equipped with alum-
inum pistons which
are not
bushed
for the
piston
pin.
Piston pins
are
locked-in
rod
type
for
both cast iron
and
aluminum
pistons,
1.
Piston pin bushing 4. Ventilated oil
2.
Piston ring ring
3.
Scraper compres- 5, Cylinder liner
Bion ring
6. Seal rings
Paragraphs 90-93
Oil Rings One venti- One ventilat-
lated type ed, with
ex-
pander
Recommended
end gap of all
rings
is .007-,012. Recommended side clear-
ance
is
.0015-,003
for
compression
rings;
.001-,002S
for oil
rings.
PISTON PINS
All Except Model
G
93,
The
piston pins
are
furnished
only
in the
standard siz.;.
Pin is
locked
in connecting
rod.
Bosses
of
iron pistons
are
fltted with
renewable bushings; aluminum
pis-
tons
are not
bushed. Connecting rods
in
B, C, CA, and RC are
offset with
respect
to big end
bearing; rods
in
WC,
WD, WD4S
and WF are
straight.
Iron pistons
for WC, WD, and WF
have
pin
bosses
of
unequal length;
on
aluminum pistons, bosses
are of
equal
length.
As
a
check
for pin fit in
piston
(piston
at
room temperature),
the flt
should
be
such
as to
prevent connect-
ing
rod
from moving when piston
and
rod assembly
is
held
in a
horizontal
position,
yet a
slight sudden movement
of
the
piston will cause
rod to
move.
On B,
C,
CA,
and
RC, assemble pins
to rods
so
that
pin
will
be
centered
between bosses.
ALUMINUM PISTONS—WC-WD-
WD4S-WF. Pistons should
be
assem-
bled
to the
connecting rods
as
follows:
On
all 4
units
the
connecting
rod
piston
pin
clamp screw should face
the camshaft,
and the
arrow stamped
on
top of
piston shoiild point toward
front,
and the
piston slot should face
away from
the
camshaft. Assemble
1-3
2-4
Fig.
AC37-Models WC,
WD,
WD45
and
WF
piston
pin to rod
installation
for
models
equipped with aluminum pistons. Piston
pins
are of the
locked-in
rod
type.
Num-
bers
1 & 3
units
are
assembled
as
shown
at
the
left.
Numbers
2 & 4
units
are as-
sembled
as
shown
at the
right.
19
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