GMC 1990 Light Truck Repair Manual page 363

Figure 18—Measuring Ring Clearance
The oil control rings are three piece types,
consisting of two rails and an expander.
Expander.
Lower rail.
Upper rail.
Upper compression ring. Use J 25220 (figure 5).
Lower compression ring. Use J 25220 (figure 5).
Flex all rings to make sure the rings are free. If
binding occurs at any point the cause should be
determined. If binding is caused by the ring groove,
correct by dressing the groove with a fine cut file. If
binding is caused by a distorted ring, check a new
ring.
Measure (Figure 18)
• Ring clearance. Use a feeler gage as shown in
figure 18. Compare with " Specifications" in
the proper section.
Installing the Piston Rings
(6.2 L Engines)
• All compression rings are marked on the upper side
of the ring. When installing the compression rings,
make sure the MARKED SIDE IS TOWARD THE
TOP OF THE PISTON.
GENERAL ENGINE MECHANICAL 6A-11
The top compression ring is a keystone type.
The oil ring is a two-piece type, consisting of an
expander and a scraper ring.
Measure (Figures 7 and 16)
Ring end gap as follows:
1. Select rings comparable in size to the piston
being used.
2. Slip the compression ring in the cylinder bore;
then press the ring down into the cylinder bore
about 7 mm (
sure the ring is square with the cylinder wall.
3. Measure the space or gap between the ends
of the ring with a feeler gage (figure 16).
4. Refer to " S pecification s" in the proper
section.
5. If the gap between the ends of the ring is not
as specified, remove the ring and try another
for fit.
Inspect (Figure 17)
L*
Ring fit as follows:
1
. Fit each compression ring to the piston on
which it is going to be used.
2. Slip the outer surface of the top and second
compression ring into the respective piston
ring groove (figure 17), to make sure that the
ring is free. If binding occurs at any point, the
cause should be determined. If binding is
caused by the ring groove, correct by dressing
the groove with a fine cut file. If the binding is
caused by a distorted ring, check a new ring.
Assemble
*
• Piston rings. Refer to the instructions furnished with
the parts package.
tpji Measure (Figure 18)
• Ring clearance. Use a feeler gage as shown in
figure 18. Compare with " Specifications" in the
proper section.
1 4
/ -inch) above ring travel. Be