Chevrolet 1977 light duty truck, Service Manual

Page: 477 / 861

Fig. 6A-66--Checking Ring in Groove
Piston Rings
All compression rings are m arked on the upper side
o f the ring. W h e n installing compression rings, make
sure the m ark ed side is toward the top o f the piston. The
top ring is chrom e faced, o r treated with m olybdenum
for m ax im u m life.
T he oil control rings are o f three piece type,
consisting o f two segments (rails) and spacer.
1. Select rings co m p arab le 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
1 /4 " (above ring travel). Be sure ring is square with
cylinder wall.
3. M easu re the space or gap between the ends o f
the ring with a feeler gauge (fig. 6A-65).
4. If the gap between the ends o f the ring is below
specifications, remove the ring and try another for fit.
5. Fit each compression ring to the cylinder in
which it is going to be used.
6. If the pistons have not been cleaned and
inspected as previously outlined, do so.
7. Slip the outer surface o f the top and second
compression ring into the respective piston ring groove
an d roll the ring entirely a ro u n d the groove (Fig. 6A-66)
to m ake sure that the ring is free. If binding occurs at
any point the cause should be determ ined, and if caused
by ring groove, remove by dressing with a fine cut file. If
the bin d in g is caused by a distorted ring, check a new
ring.
8. Install piston rings as follows (fig. 6A-67).
N O T E : Tools J-8020 (3-9/16"), J-8021 (3-7/8"),
J-8032 (4"), J-22249 (3-15/16"), J-22147 (4-3/32"),
and (J-22250 (4 -1 /4 ") are available for this
purpose.
a. Install oil ring spacer in groove and insert
anti-rotation tang in oil hole.
b. Hold spacer ends butted and install lower
steel oil ring rail with gap properly located.
c. Install upp er steel oil ring rail with gap
properly located.
d. Flex the oil ring assembly to m ake sure ring
is free. If binding occurs at any point, the cause should
be determ ined, and if caused by ring groove, remove by
dressing groove with a fine cut file. If binding is caused
by a distorted ring, check a new ring.
e. Install second compression ring e x p an d er then
ring with gaps properly located.
f. Install top compression ring with gap properly
located.
9. Proper clearance o f the piston ring in its piston
ring groove is very im p o rta n t to provide p roper ring
action and reduce wear. Therefore, when fitting new
rings, the clearances between the surfaces o f the ring
groove should be m e a su re d (fig. 6A-68). (See
Specifications.)