Pontiac FIREBIRD 1972 Service Manual page 551

SIX CYLINDER ENGINE 6-39
Fig. 6-61 Measuring Cylinder Bore
Fig.
6-63
Measuring Cylinder Gauge
HONING OR BORING
If a piston in excess of .005" oversize is to be installed, the
cylinder should be bored, rather than honed, to effect a
true bore.
When honing to eliminate taper in the cylinder (when
installing .005" oversize piston), full strokes of the hone
in the cylinder should be made in addition to checking
measurement at top, middle and bottom of bore repeat-
edly.
When boring, always be sure the crankshaft is out of the
way of the boring cutter when boring each cylinder.
Crankshaft bearings and other internal parts must be cov-
ered or taped to protect them during boring or honing
operation. When taking the final cut with a boring bar,
leave .001" on the diameter for finish honing to give the
required piston to cylinder clearance specifications. (Hon-
ing or boring operation must be done carefully so that
specified clearance between pistons, rings, and cylinder
bores is maintained).
Fig. 6-62 Normal Cylinder Wear Pattern
By measuring the piston to be installed at the sizing points
(Fig. 6-64) and adding the mean of the clearance specifica-
tion, the finish hone cylinder measurement can be deter-
mined. It is important that both the block and piston be
measured at normal room temperature, 60'
-
90°F.
After final honing and before the piston is checked for fit
each cylinder bore must be thoroughly cleaned. Use soapy
water solution and wipe dry to remove all traces of abra-
sive. If all traces of abrasive are not removed, rapid wear
of new rings and piston will result.
Intermixing different size pistons has no effect on engine
balance as all Pontiac pistons from standard size, up to
.03OU oversize, weigh exactly the same. Pontiac does not
recommend boring beyond .010" during warranty period
so that, if necessary, engine can be serviced at high mileage
without cylinder block replacement.