SERVICE MANUAL
tightening torque values, have been
used. Ear
l
y models
used
cadmium plated
(bright finish) nuts while later models
use phosphated (dull black finish) nuts.
Do not intermix the different types of
nuts. Connecting rod nuts should be
tightened to the following torque values:
61
N
·
m
(45
ft.-lbs.) for cadmium plated
nuts and
81
N
·
m
(60
ft.lbs.) for
phosphated nuts.
PISTONS, SLEEVES AND RINGS
All Diesel Models
73.
The aluminum alloy, cam ground
pistons a1·e supplied in standard size on
ly and are available in a kit consisting
of piston, pin and rings for one cylinder.
The toroidal combustion chambe1· is ofT
set in piston crown and piston should be
marked "FRONT" or "F" for proper
assembly as shown in Fig.
71.
If
"FRONT" or "F" marking is not present
on piston cmwn, assemble piston to con
necting rod with the cavity ofiset
towards side of rod that is stamped with
cylinder identification number.
Five piston rings (Fig.
72}
are used in
engines with serial number suffix "D"
or "DL." The first (top) nng is chrome
plated, parallel faced and may be in
stalled either side up. The second ring
is cast iron, parallel faced and may also
be installed either side up. The third
compression ring consists of four steel
segments as shown in Fig.
72.
The seg
ments appear practically nat when not
under compression, but when com·
pressed
as
shown in Fig.
73
the ends will
curl up (or down if ring is turned over).
Ring ends should curl down on segment
installed at bottom of groove, up on sec
ond, down on third and up on top seg
ment. Space end gaps of the four
segments
180
degrees apart from
nearest segment. The fourth ring is
Fig. 72-Draw/ng of five-ring piston showing
cross-sect/on of the rings correctly lnstelled. Refer
to text.
Fig. 73-The four-segment
ring lnstelled In the third
groove of five-ring pistons
must be correcl/y assembled
es described In text
chrome plated, laminated, oil control
ring.
1b
install, flrst install the internal
expander, install the two lower rails,
spiral ring, then the top two rails. Stag
ger the gaps
of
the ring segments around
the piston. The fifth (bottom) oil control
ring is nondirectional and may be in·
stalled with either side up. Piston and
ring specifications
are
as follows:
F
i
ve-Ring Pistons
Piston Skirt
Diameter•
.
. .
.
.
. . 91.326-91.351
mm
(3.5955-3.5965
in.)
Ring Side Clearance
in Groove-
Thp
&
Second . .
.
.
.
.
. . 0.05-0.10
mm
(0.002-0.004
in.)
Third
&
Fourth . . . . . Not applicable
Bottom . .
.
.
.
.
. . .
.
. .
. 0.05-0.10
mm
(0.002-0.004
in.)
Ring End Gap-
Thp
.
.
. .
.
. . . .
.
. . . . . . 0.36-0.76
mm
(0.014-0.030
in.)
Second
.
.
. .
.
. .
.
. . . . . 0.28-0.69
mm
(0.01 1-0.027
in.)
Third
(each segment) .
.
.
.
.
0.25-0.38
mm
(0.010-0.015
in.)
Fourth (each rail) .
.
. .
0.46-0.94
mm
(0.018·0.037
in.)
Fig. 74-Draw/ng of four-ring pltton 1how/ng
cross-section of rings correctly lnstelled. Refer to
text.
Paragraph
73
Bottom
. .
.
.
.
.
.
.
.
. .
.
. 0.28-0.69
mm
(0.011·0.027
in.)
• Skirt diameter meabured at bottom of
piston,
90°
from piston pin bore.
Fou1· piston rings (Fig.
74)
are used in
engines with serial number suffix "DS"
or "DLS." The first (top) ring is chrome
plated and may be installed either side
up.
The second and third rings
are
alike
and are internally stepped. The
groove
cut into the inner diameter should be
toward top
as
shown in F
i
g.
74.
The bot·
tom (fourth) ring
1s
nondirectional with
a coil spring expander. Install the ex
pander groove first being sure the latch
pin engages both ends of spring
as
shown
in Fig.
75,
then install the ring over the
expander. Piston and ring specifications
are as follows:
Four-Ring
Pistons
Piston Skirt
Diameter• . .
.
. . . .
91.336-91.361
mm
(3.5959-3.5969
in.)
Ring Side Clearance
in Groove-
'Ibp
.
.
.
. . .
.
.
.
. . . . . . . 0.05-0.10
mm
(0.002-0.004
in.)
Second
&
Third
.
. .
. . . 0.05-0.10
mm
(0.002-0.004
in.)
Bottom
.
.
. .
.
.
. . . .
.
. . 0.05-0.11
mm
(0.002-0.0045
in.)
Fig. 75-The expander for
o/1
control ring of four
ring piston must heve the latch pin connecting
ends of expender spring
33
