Service manual
Main
Moving
Parts
• Pistons and piston rings
The
['Istons and piston rings are shown in Fig. 26.
If
the
cyl inder
Imers have been bored oversi7e. oversize pistons
anti rings must
be
used. The piston
is
made
of
high silicon
AI·Alloy
and
is
cam ground. The top compression ring
is
a
chrOln£' plated keystone type. the second compression ring
is
discontinuous and undercut and the
oil
control
ring
is
of
the
standilrd expansion type.
s:
End
gap
of
rings
on
poston
in
cylinder
I Diameter
of
piston
skirt
thru
t
of
piston
pin
bore
E:
Diameter
of
piston
skirt
perpendicular
to
piston
pin
I 0.10i'l . .J.2.5mm)
III
r~
I
L~,
.----1
lJ2.0Bl - 0.OB2in.
(2JjliF-
2.070mm)
0.191-
0.19Bin.
(5.010:::
5.030m"'1
0.905
'-
0.906in.
(23.000 -
23.013mm)
0.012-
O.OlB,'!.:..,
(El!
(0.30 - 0,45Ff1m) i
0.10in. (2,49mm) : i
t
--
-.'=CC.".
0.Oj6B_O._t::J!121n·_n I
(1.950-1.962mm)
i !
i...
0,1,957- 0.1965in."J
rt.--
181
I
f4.91B-4.990mm)
i i
~
I
L--<i.\
J
0.010-
O.018i~
.'
(1i.'25-
0.45mm)
Fig.
26. Standard Dimensions
of
Piston
and Piston Rings
~
Standard size
Over size
IA
2.992in.
3.012in.
(76mml
(76.5mml
r----
-
-
---
I
2.986
2.987in.
3.005
-
3.006in.
16
(75839
75.859mml
(76.339-
76.359mml
r---
2.989
.
2.990in.
3.008
-
3.009;n.
24
E
(75.915
75.935mml
06.415
-
76.435mml
Over
Sl7e
Name
of
Part
(O.5mrn)
Piston
05
0.02in.
Piston
ring
05
f--
H.P.
H.P.
• Crankshaft and connecting rod
(1) The crankshaft
is
a heat treated steel
alloy
forging. The
crank pins are
induction
hardened
for
additional
wear
resistance.
Crankshaft endplay
is
0.006
to
0.012
in.
(0.15
to
0.31
mm).
(2) The
crankpin
bearings are
aluminum.
When installing the connecting rods:
a)
Clean
both
surfaces
thoroughly.
b)
Apply
engine oil to the threads
of
the connecting rod
capscrews before installing and tighten each to 27
to
30.4 ft·lbs. (3.7
to
4.2 kg-mi.
The bearing
caps
are matched
to
each connecting rod
and should
not
be
interchanged. Also. since there are
variations in machining
from
side
to
side, each bearing
cap and connecting rod are marked and should be
assembled
so
that the marks line up.
(3)
In the event that the crankpins become
worn
and are
no
longer serviceable, undersized bearings
may
be used.
When installing the undersize bearings observe the
fol·
lowing precautions
a)
Machine the
crankpin
diameter and radii
to
within
a
few
thousandths
of
the correct dimensions and
finish grind
to
the exact dimensions.
b)
After
finish grinding the bearing diameter and the radii,
chamfer the diameter
of
the oil hole
with
an
oilstone.
If
this
IS
not
done
an
oil
film
will
not
form
and the
bearing
will
sieze.
c)
The
crankpin
should always
be
super-finished
to
0000016
in.
(00004
mm)
or
less.
d)
Select the bearing
from
the chart that necessitates
the
removal
of
the least
amount
of
metal
from
the crank-
pin.
Do
not
deviate
from
the
chart dimensions
as
the
bearing
life
will
be
reduced
if
they are machined.
e)
To
determine the running clearance, assemble the con-
necting
rod,
bearing cap and bearing
as
described in
section 2 and measure the diameter anywhere
within
the 120
0
angle indicated in Fig.
28
and subtract
the
crankpin
diameter
from
this figure.
f) . The piston
pin
bushings are
of
lead bronze.
The inside diameter
of
the bushing should
be
finished
to
0906
to
0.907 in. (23.025
to
23.040
mm).
Mark
05
OS
16
H.P.
05
OS
Cylinder
liner
3012
to
3.013in. (76.500
to
76.519mm)
24
H.P.
(12f.1R max.
to
2pR max.)
by
honing
>---------
------
--_
...
_--
--
( 11)