Chevrolet 70 Series 1970, Service Manual

Page: 384 / 841

GASOLINE ENGINES 6A-13
5. A fter radiator h ose is connected, and sen d - 6. Rem ove cylinder head b o lts,
ing unit in stalled , f ill cooling sy ste m and inspect 7. Lift cylinder head off cylinder block, then
fo r le a k s. rem ove head gask et, and clean carbon d ep osits
from cylinder head, p isto n s, and cylinder block.
CYLINDER HEAD AND GASKET
REPLACEMENT
To rep la ce either cylinder head an d /o r gasket
on ga so lin e engines follow the in stru ction s a s out­
lined in paragraphs follow ing. On re a r-en g in e
sch o o l b u se s, u n le ss sp e c ia l p ro v isio n s are made
in the v eh icle body d esign , it w ill be n e c e ssa r y
to rem ove engine from c h a s s is to gain su fficien t
working sp ace to rem ove cylin d er heads. The
sh ield attached to re a r of cab support on Tilt-C ab
m odels should be rem oved to provide a c c e s s to
rea r head b olts.
CYLINDER HEAD REMOVAL
NOTE: When left-h an d head is to be rem oved
from tilt cab m odel, the tra n sm issio n control rods
m ust fir s t be rem oved.
1. D rain cooling sy ste m .
2. D isconnect exhaust pipe from exhaust m ani­
fold, then rem ove exhaust manifold and gasket.
3. R em ove valve co v er, rocker arm s and
push rod s. Identify push rods so they can be r e ­
turned to origin al p o sitio n s when in stalled . P r o ­
ced u res for replacing valve rock er arm s and
ro ck er arm c o v ers a re given p reviou sly under
r e sp e c tiv e headings.
4 . D isen gage spark plug w ir e s from plugs
and from plug w ire supports.
5. On V6 en gin es, rem ove water outlet m ani­
fo ld a s p reviou sly in stru cted under "Manifold
R eplacem ent."
NOTE: If only one cylin d er head is to be r e ­
m oved, the intake m anifold (and w ater outlet m ani­
fold on V6 engines) may rem ain in p la ce on oppo­
s it e head, in which c a se carburetor con trols and
fu el lin e need not be disconnected. H owever, it
w ill be n e c e ssa r y to lo o sen the m anifold attaching
p a rts to p erm it cylin d er head to r is e off locating
d ow els.
CYLINDER HEAD INSTALLATION
NOTE: If valve lifte r s have been rem oved,
lubricate lift e r s with sp e c ia l b reak -in compound
and in sta ll in resp e c tiv e b o r e s.
1. Check gasket su rfa ce on cylinder head and
on cylinder block. S urfaces must be clean . P la ce
cylinder head gasket on top of cylinder b lock with
word "TOP" facing upw ards. D ow els w ill lo ca te
gasket. If available, guide pins (fig. 11) may be
tem p orarily in sta lled in two cylinder head bolt
h o les to lo ca te head a s it is low ered into p la ce.
2. Set cylinder head in p la ce on gasket with
dow els in block engaged with mating h oles in c y l­
inder head. Apply S.A .E . #10 engine o il on threads
and heads of cylin d er head b o lts, then in sta ll c y l­
inder head b olts and draw head down gradually.
Finally tighten cylinder head b olts in sequence
shown in figure 19 on V6 engines, or a s shown in
figu re 20 on V8 en gin es. Tighten bolts gradually to
fin al torque of 60 to 65 foot-pounds on V6 engines.
3. In stall one cran k case ventilation valve in
each head on V6 en gin es.
4. Install exhaust m anifolds using new gask ets
and bolt lo ck s. Tighten exhaust m anifold b olts to
15 to 20 foot-pounds torque. Connect exhaust pip es
to m anifolds.
5. U se new intake m anifold gask ets between
intake m anifold and cylinder heads, and bolt intake
m anifold (and w ater outlet manifold on V6 engines)
in p la ce, tightening m anifold b olts evenly to sea t
p arts squarely at g a sk e ts. C orrect intake m anifold
torque is 20 to 25 foot-pounds torque.
6. L ubricate push ro d s, and p osition at valve
lifte r s in origin al lo c a tio n s. Set valve rock er arm
a ssem b ly on cylin d er head and bolt in p la ce follow ­
ing in stru ction s p reviou sly given under "Valve
O perating M echanism R eplacem ent."
7. In sta ll valve rock er arm co v er, u sin g new
gasket.
8. Connect spark plug w ir e s, f ill cooling s y s ­
tem ; then sta rt and run engine until thoroughly
w arm ed up (160°). U se torque w rench and adapter
(fig. 4) to final tighten cylinder head b o lts. Check
intake m anifold bolt torque. "Torque W rench Sp eci­
fication s Chart" is at end of th is sectio n .
9. Adjust valve la sh to sp ecifica tio n s liste d
in appropriate “ Tune-Up Chart” on page 6A -8.
CRANKSHAFT PULLEY AND HUB
REPLACEMENT
Figure 12-C ylin d er Head Bolt Tightening
On so m e m odels the crankshaft pulley is not
Sequence on V6 Engine readily a c c e s s ib le u n le ss the radiator core i s fir s t
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL