Chevrolet 1977 light duty truck, Руководство по обслуживанию

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N O T E : This o p e ra tio n is done by grin d in g the port
side with a 30 degree stone to lower seat and a 60
degree stone to raise seat.
5. Remove e x p a n d in g pilot and clean cylinder
head carefully to remove all chips and grindings from
above operations.
6. M easure valve seat concentricity (fig. 6A-36V).
N O T E : Valve seats should be concentric to within
.002" total indicator reading.
VALVES
Valves th at are pitted can be refaced to the p roper
angle, insuring correct relation between the h ead and
stem on a valve refacing m echanism . Valve stems which
show excessive wear, or valves
that are w arped
excessively should be replaced. W h e n a valve head which
is w arp ed excessively is refaced, a knife edge will be
g round on p a rt or all o f the valve h ead due to the
a m o u n t o f metal th at must be removed to completely
reface. K n ife edges lead to breakage, b u rn in g or p re ­
ig nition due to heat localizing on this knife edge. If the
edge o f the valve head is less th an 1 /3 2 " thick after
grinding, replace the valve.
Several different types o f e q u ip m e n t are available
for refacin g valves. T he reco m m en d atio n o f the
m a n u fa c tu re r o f the e q u ip m e n t being used should be
carefully followed to attain pro p er results.
Reconditioning
1. If necessary, dress the valve refacing machine
g rin d in g wheel to make sure it is smooth and true. Set
chuck at angle specified for valve. R efer to specifications.
2. C la m p the valve stem in the chuck o f the
m achine.
3. Start the grin d er and move the valve head in
line with the g rin d e r wheel.
4. T u r n the feed screw until the valve head just
contacts wheel. Move valve back and forth across the
wheel and regulate the feed screw to provide light valve
contact.
5. Continue g rin d in g until the valve face is true
and smooth all a round the valve. If this makes the valve
head thin ( 1 /3 2 " min.) the valve must be replaced as the
valve will overheat an d burn.
6. Remove valve from chuck and place stem in
" V " block. Feed valve squarely against g rinding wheel to
grind any pit from rocker arm end o f stem.
N O T E : Only the extreme end o f the valve stem is
h ard en ed to resist wear. Do not grind end o f stem
excessively.
7. A fter cleaning valve face and cylinder head
valve seat o f grin d in g particles, make pencil m arks about
1/4" ap art across the valve face, place the valve in
cylinder h ead and give the valve 1/2 turn in each
direction while exerting firm pressure on h ead o f valve.
8. Remove valve and check face carefully. If all
pencil marks have not been removed at the p oint of
contact with the valve seat, it will be necessary to repeat
the refacing operation and again recheck for p roper
seating.
9. G r in d and check the rem ain in g valves in the
same m anner.
T O R S IO N A L D A M PE R
Removal
1. Remove fa n belt, fa n and pulley.
2. R em ove the r a d ia to r shro u d assem bly as
outlined in Section 6B.
NOTE: If additional operations (such as cam shaft
removal) are not being perform ed, the rad iato r
removal will not be necessary.
3. Remove accessory drive pulley then remove
d a m p e r retaining bolt.
4. Install Tool J-23523 on d a m p e r then, turning
puller screw, remove d a m p e r (fig. 6A-37V).