Figure 11B-119. Checking Piston Pin
Retainer for Proper Sealing
tector J 23987-01 (Figure 11B-119 on
Place the suction cup
over the retainer and hand operate the
lever to pull a vacuum of ten inches on
the gauge. A drop in the gauge reading
i n d i c a t e s air leakage at the retainer.
F i g u r e 11B-120. Measuring
Piston-to-Liner Clearance
Fitting Piston
If any bind occurs between the piston
Measure
the
skirt
piston
a n d t h e l i n e r , examine the piston and
diameter
lengthwise and crosswise of the piston
liner for burrs.
Remove burrs with a
p i n b o r e . Measurements should be taken
fine hone (a flat one is preferable) and
at room temperature (70F or 21C).
recheck the clearance.
The piston-to-liner clearance, with new
parts, will vary with the particular pis-
F i t t i n g Piston Rings
ton and cylinder liner.
A maximum
clearance of 0.012" is allowable with used
Each piston is fitted with a fire ring, two
parts.
compression r i n g s a n d t w o o i l c o n t r o l
rings
(see
page
With the cylinder liner installed in the
11B-76).
cylinder block, hold the piston skirt up-
side down in the liner and check the
The top (fire) ring and the upper com-
clearance in four places 90 apart (see
pression
ring
(second
groove)
are
pre-stressed.
Both are identified by a
small indentation mark on the top side.
Use feeler gauge J 5438-01 to check the
A two-piece oil control ring is used in
clearance. The spring scale, attached to
both oil ring grooves in the pistons.
the proper feeler gauge, is used to mea-
sure the force in pounds required to
A l l n e w p i s t o n rings must be installed
withdraw the feeler gauge.
whenever a piston is removed, regard-
less of whether a new or used piston or
Select a feeler gauge with a thickness
cylinder liner is installed. Refer to the
that will require a pull of six pounds to
parts manual to select the current piston
remove.
The clearance will be 0.001"
rings.
greater than the thickness of the feeler
g a u g e u s e d , i . e . , a 0.004" feeler gauge
Insert one ring at a time inside of the
w i l l indicate a clearance of 0.005" when it
cylinder liner and far enough down to be
is withdrawn with a pull of six pounds.
within the normal area of ring travel.
Use a piston skirt to push the ring down
The feeler gauge must be perfectly flat
to be sure it is parallel with the top of
and free of nicks and bends.
the liner.
Then measure the ring gap
E n g i n e (Less Major Assemblies)
