Chevrolet 70 1969 Series, Shop Manual

Page: 685 / 913

E N G IN E 6-14
cessive wear, new pistons should be installed. Measure
piston pin bores in piston bosses, and compare with diam ­
eter of pins. If excessive clearance exists, obtain oversi/e
pins for use at assembly. Also check fit of piston pins in
connecting rod bushings as directed below under “ C o n ­
necting Rod and Bearing Inspection."
!f equipment is available, employ Zyglo inspection
method to detect cracks in aluminum pistons.
NOTE: New service pistons are fitted with pis­
ton pins.
Connecting Rod and Bearing Inspection
1. Connecting Rod inspection
With bearing halves removed Irom rod and cap. in­
stall cap and tighten rod bolt nuts to 60 foot­
pounds torque. Check bore at lower end for elonga­
tion. If bore is out-of-round, the rod should be
replaced or reconditioned. If bore is round and
within specifications as given at end of this section,
make careful visual inspection of piston pin bushing
for evidence of wear. Test fit of piston pin in bush­
ing by measuring pin 0.1). and bushing 1.1). At 70
degrees I-'., there should be a clearance of 0.0001
to 0.0006 inch. When nccessar\. replace bushing
as directed later under "'Connecting Rod Repair."
2. Connecting Rod Alignment
Connecting rod assembly should be placed ir suitable
aligning fixture to determine il rod is twisted or bent.
Piston pin hole must be parallel with axis of crank-
pin hole in all planes within .002 inch in 7 inches.
Straighten or replace if not within limits.
3. Bearings
Carefully inspect connecting rod bearing halves for
evidence of scoring, chipping, or flaking out of
bearing melai. if a visual inspection reveals any of
these defects, replace with new pair of bearing
halves. Measure each bearing half with accurate
reading tube micrometer. T ake measurement at right
angle to split line (fig. 15). Dimensions for new
bearing halves are given in "Specifications" at end
of this section,
C O N N E C T IN G RO D REPAIR
If inspection indicates that connecting rod piston pin
bushing requires replacement, follow the procedure given
below to install new bushings which are available for serv­
ice. Sectional view of connecting rod at upper end is
shown in Figure 4X.
1. Remove old bushing using driver and arbor press.
2. Inspect bore in upper end of connecting rod. Measure
bore IT), which must be 1.3125 to 1.3135 inches to
assure satisfactory fit of new bushing. Clean oil pas­
sage at top of rod.
3. Support connecting rod and press new bushing into
place, using care to align oil hole in bushing with hole
in top of connecting rod.
4. Diamond bore bushing to provide clearance of 0.0001
to 0.0006 inch clearance when piston pin is inserted in
bushing. Suitable fixture must be used to assure fin­
ished hole alignment. Check pin fit with parts at 70
degrees F.
5. Dress bushing edges to remove any portion of bushing
extending beyond edge of rod. If edges are burred or
sharp, use scraper or large reamer to provide chamfer
at edges of bushing. Be sure oil passage in top of rod
is free from cuttings,
6. With connecting rod alignment fixture, check the con­
necting rod for bent or twisted conditions as instruct­
ed previously under “ Connecting Rod Alignment."
Figure 2 1 — C y lin d e r N u m b e r in g A rr a n g e m e n t a n d Size Selection N u m ­
bers
Figure 2 2 — Checking Piston Ring G a p