Chevrolet 70 1969 Series, Shop Manual

Page: 644 / 913

POWER BRAKE 5-35
Figure 6— Alignment of Connecting Rod Journal with Cut-<
Crankcase Bearing Bore
CRANKSHAFT A N D BEARIN G
REMOVAL
1. R otate crankshaft so that connecting rod front bear­
in g j o u r n a l is a l i g n e d w i t h c u t - o u t s e c tio n of
crankcase front bearing bore (fig. 6).
2. T ap front bearing outer race O N L Y with long punch
to remove bearing and crankshaft. Rem ove crankshaft
and front bearing from crankcase through front cut­
out section (fig. 6).
3. R ear insert type bearing (which is not serviced separ­
ately) was removed as part of rear bearing cap.
NOTE: DO NOT remove crankshaft bearing
from crankshaft unless inspection shows neces­
sity for removal.
CLEANING, INSPECTION, A N D REPAIR
After disassembly and before inspection, wash all parts
thoroughly in a suitable cleaning solvent. M ak e sure all
carbon deposits are removed from pistons and cylinder
head. Prod drilled oil passages in crankshaft to m ake sure
passages are open. Scrape all carbon from piston ring
grooves in pistons.
INSPECTION A N D REPAIR
Discard all gaskets and crankshaft front oil seal, and
obtain new parts for assembly. Inspect balance of parts
and m ake necessary repairs or replacem ent as directed
below, referring to Figure 1 for identification of parts.
CYLINDER HEAD AND VALVES
1. Exam ine cylinder head for cracks and dam aged
threads in tapped openings. Replace head if any d a m ­
age is evident. Be sure all water passages are free
from foreign m atter if com pressor is water-cooled
type.
2. Exam ine discharge valves and valve seats. If valves
are deeply grooved on one side where they contact the
seats, they m ay be turned over to use the unworn
side. If valves have been previously turned over so
that both sides are worn, or if otherwise dam aged, re­
place with new parts. If valve seats are pitted or o th ­
erwise dam aged, replace with new parts. If discharge
valves are to be turned over or if new valves or seats
are to be used, valves m ust be lapped to seats, using
lapping com pound. A fter lapping, thoroughly clean
lapping com pound from valves and seats.
NOTE After lapping each valve to a seat, keep
valve and seat together as a matched set; each
valve must be installed on the seat to which it
was lapped.
3. Inspect inlet valves and inlet valve guards for pitting
or corrosion. If corrosion does not readily clean off
without leaving pits, replace with new parts. M ake
sure dowel pin is tight in valve guard.
4. Inspect inlet valve plungers for distortion and for evi­
dence of wear at both ends.
5. Check inlet valve plunger springs and discharge valve
springs for free length and com pression. If not within
limits listed in “ Specifications” at end of this manual,
replace with new parts.
6. Exam ine governor attaching studs for distortion or
dam aged threads. Replace studs if dam aged.
PISTONS, CO N N ECTIN G RODS,
AND BEARINGS
1. Exam ine pistons for scoring, cracks, or dam age of
any kind. M easure outside diam eter of each piston
and com pare this diam eter with inside diam eter of
cylinder bore.
NOTE When measuring the outside diameter of the
piston make sure that the micrometer is at a 90
degree angle to the piston pin bore. This will
enable correct measurement.
If the piston diameter is more than 0.009-
inch smaller than the cylinder bore, piston must
be replaced with a new part. Service pistons
are available in 0.010 inches, 0.020 inches and
0.030 inches oversize.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M A N U A L