Buick LeSabre 1965 Service Manual page 66

2 - 4 4 BEARINGS
ENGINE
torque to avoid distortion of bores
in final assembly. Always be sure
the crankshaft is out of the way of
the boring cutter when boring
each cylinder. When taking the
final cut with boring bar leave
.001" on the diameter for finish
honing to give the required clear-
ance specified below.
When honing cylinders use clean
sharp stones of p r o p e r grade
for the amount of metal to be
removed, in accordance with in-
structions of the hone manu-
facturer. Dull or dirty stones cut
unevenly and generate excessive
heat. When using coarse or me-
dium grade stones use care to
leave sufficient metal so that all
stone marks may be removed with
the fine stones used for finishing
to provide proper clearance.
When finish honing, pass the hone
through the entire length of cyl-
inder at the rate of approximately
60 cycles per minute. This should
produce the desired 45 degree
cross hatch pattern on cylinder
walls which will insure maxi-
mum ring life and minimum oil
consumption.
It is of the greatest importance
that refinished cylinder bores are
trued up to have not over .0005"
out-of-round or taper. Each bore
must be final honed to remove all
stone or cutter marks and provide
a smooth surface. During final
honing, each piston must be fitted
individually to the bore in which
it will be installed and should
be marked to i n s u r e correct
installation.
After final honing and before the
piston is checked for fit, each
cylinder bore must be thoroughly
washed to remove all traces of
abrasive and then dried thor-
oughly. The dry bore should then
be brushed clean with a power-
driven fibre brush. If all traces
of abrasive are not removed,
rapid wear of new pistons and
rings will result.
Figure 2-45—Using Telescope Gauge
in Cylinder Bore
Pistons must be fitted with the
use of accurate micrometers ca-
pable of reading to one ten thou-
sandths of an inch.
A satisfactory method of fitting
pistons is as follows:
1. Expand a telescope gauge to
fit the cylinder bore at right
angles to the piston pin and be-
tween 1-1/2" and 2" from the top
of the bore. See Figure 2-45.
2. Measure the telescope gauge.
See Figure 2-46.
3. Measure the piston to be in-
stalled. See Figure 2-44. The
piston must be measured at right
angles to the piston pin below the
oil ring groove.
4. The tolerance of piston clear-
ance is .001" to .0016".
Both block and piston must be at
very nearly the same temperature
when measurements are taken or
e r r o r s due to expansion will
occur. A difference of 10°F be-
tween parts is sufficient to pro-
duce a variation of .0005".
e. Fitting New Piston Rings
When new piston rings are in-
stalled without reboring cylin-
ders, the glazed cylinder walls
should be slightly dulled, but
without increasing the bore diam-
eter, by means of the finest grade
of stones in a cylinder hone.
Figure 2-46—Measuring Telescope
Gauge
New piston rings must be checked
for clearance in piston grooves
and for gap in cylinder bores;
however, the flexible oil rings
are not checked for gap. The cyl-
inder bores and piston grooves
must be clean, dry and free of
carbon and burrs.
With rings installed, check clear-
ance in g r o o v e s by inserting
feeler gauges between each ring
and its lower land because any
wear that occurs forms a step
at inner portion of the lower land.
If the piston grooves have worn
to the extent that relatively high
steps exist on the lower lands,
the piston should be replaced be-
cause the steps will interfere with
the operation of new rings and the
ring clearances will be excessive.
Piston rings are not furnished in
oversize widths to compensate for
ring groove wear.
When fitting new rings to new
pistons the side clearance of the
compression rings should be
.003" to .005" and side clearance
of the oil ring should be .0035"
to .0095".
To check the gap of compression
rings, place the ring in the cyl-
inder in which it will be used,
square it in the bore by tapping
with the lower end of a piston,
then measure the gap with feeler
gauges. Piston rings should not
have less than .015" gap when
placed in cylinder bores. If gap