Chevrolet 70 1969 Series Shop Manual page 661

POWER BRAKE 5-52
NOTE: DO NOT file or lap bearing caps or rods
to take up clearance; always use new bearing
inserts if clearances are excessive.
CRANKSHAFT
C ra n k s h a ft jo u rn a ls should not be out-of-round m ore
than 0.001 inches, ridged or scored. If grinding is neces­
sary, do not grind fillets at ends of journals. C onnecting
rod bearing inserts are available in 0.010 inches, 0.020
inches, and 0.030 inches undersize for reground c ra n k ­
shafts. C heck m ain bearing jo u rn a ls for excessive wear.
D im ensions should be such th a t ball bearing is a press fit
on journal.
CRANKSHAFT BEARING
E xam ine bearing for w ear or flat spots by rotating
races. If any roughness is detected bearing should be re­
placed with new bearing.
COMPRESSOR REPAIR
DISCHARGE VALVES AND SEATS
1. R em ove slight scratches and pits from discharge valve
seats. Use lapping stone, grinding com poun d, lapping
disc, and valve grinding tool.
2. Place discharge valves on valve seats, install discharge
valve springs in cap nuts, an d thread cap nuts firmly
into cylinder head. T o test discharge valves for leak­
age, connect air line to discharge port in cylinder
head. Apply 100 pounds air pressure to valves and
apply soap suds to discharge valve openings in botto m
of cylinder head. L eakage in excess of a one-inch
bubble in one second is not permissible. If leakage is
excessive, leave air pressure applied. U sing a fiber or
a hardw ood dow el and a light ham m er, ta p valves off
seats several tim es. This should im prove fit of valve
on seat. C heck leakage a ro u n d top of discharge valve
cap nuts by applying so ap suds to this area. N o leak­
age is perm issible. Shut off air pressure and discon­
nect line from cylinder head.
3. R em ove discharge valve seats too badly worn for re­
facing. T h re a d new seats into head and tighten firmly.
W ith new valves, discharge valve travel should be
from 0.056 inches to 0.070 inches for 12 cu.-ft. m od-
NOTE: Refer to Figure 15 while assembling air
compressor.
CRANKSHAFT INSTALLATION
BELT-DRIVEN TYPE
1. Install ball bearing on front of cran ksh aft. Press bear-
INLET VALVES A N D SEATS
1. R em ove slight scratches or pits from inlet valve seats.
2. Inlet valves not badly w orn or d a m ag e d can be re­
CONNECTING ROD BUSHINGS
placem ent, press old bushings out of connecting rods.
Press new bushings in, m aking sure the oil holes in the
bushings line up with the oil passages in the connecting
rods. Bushings m ust then be ream ed, honed, or bored to
provide 0,0001 inches to 0.0006 inches clearance on piston
pin.
cloth to rem ove all abrasive m aterial.
ASSEMBLY OF
COMPRESSOR
2. Position th ru st washer on the rear end of cran k sh aft
3. Install rear end cover oil seal in groove of end cover.
4. Install rear end cover and bearing assem bly against
5. Install cap screws and w ashers attaching end cover to
P L A S T IG A G E SC A L E
C O N N E C T IN G H
R O D C A P S
Figure 14— C h e c k in g C le a ra n ce U s in g P la stig a g e
els and .036 inches - .058 inches for 7 - 1 / 4 cu.-ft.
models.
Use lapping stone, grinding co m poun d, lapping disc,
and valve grinding tool. R eplace seats th a t ca n n o t be
repaired. D im ension from the top of the cylinder
block to the inlet valve seat should not exceed 0.145
inches, nor be less than 0.101 inches.
paired by lapping valves on a piece of crocus cloth
held on a flat surface.
If piston pin bushings in connecting rods require re­
W ipe the bushing, which has been honed, with a clean
IMPORTANT
Make sure not to overlook any of the above
"Cleaning, Inspection, and Repair" items be­
fore assembling the air compressor.
ing on cran k sh aft until inner race is seated firmly
against shoulder on cran ksh aft.
with oil grooves tow ard shoulder on shaft.
the crankcase.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M AN UA L
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