GMC 4000 Series Service Manual page 288

1. Drain cooling system .
2. Disconnect exhaust pipe from exhaust mani­
fold, then remove exhaust manifold and gasket.
3. Remove valve cover, rocker arms andpush
rods. Identify push rods so they can be returned to
original positions when installed. Procedures for
replacing valve rocker arms and rocker arm covers
are given previously under respective headings.
4. Disengage spark plug wires from plugs and
from plug wire supports.
5. Remove bolts which attach water outlet
manifold and intake manifold to cylinder head.
NOTE: If only one cylinder head is to be re­
moved, the intake manifold and water outlet mani­
fold may remain in place on opposite head, in
which case carburetor controls and fuel line need
not be disconnected. However, it will be necessary
to loosen the manifold attaching parts to permit
cylinder head to rise off locating dowels.
6. Remove cylinder head bolts.
7. Lift cylinder head off cylinder block, then
remove head gasket, and clean carbon deposits
from cylinder head, pistons, and cylinder block.
If lifters are removed ALWAYS install them in the
bores from which they were removed.
CYLINDER HEAD INSTALLATION
NOTE: If valve lifters have been removed,
lubricate lifters with special break-in compound
and install in respective bores.
1. Place cylinder head gasket on top of cylin­
der block with word "TOP" facing upwards (fig.
34). Dowels will locate gasket.
2. Set cylinder head in place on gasket with
dowels in block engaged with mating holes in cyl­
inder head. Install cylinder head bolts and draw
head down gradually. Finally, tighten cylinder head
bolts in sequence shown in figure 15. Use final
torque of 60 to 65 foot-pounds in tightening cylin­
der head bolts. A crankcase ventilation valve (fig.
31) must be in place in each cylinder head.
3. Install exhaust manifolds using new gaskets
and bolt locks. Tighten exhaust manifold bolts to
15 to 20 foot-pounds torque. Connect exhaust pipes
to manifolds.
4. Use new intake manifold gaskets between
intake manifold and cylinder heads, and bolt intake
manifold and water outlet manifold in place, tight­
ening manifold bolts evenly to seat parts squarely
at gaskets. Correct intake manifold torque is 30 to
35 foot-pounds torque.
5. Lubricate push rods, and position at valve
lifters in original locations. Set valve rocker arm
assembly (fig. 31) on cylinder head and bolt in
place following instructions previously given under
"Valve Rocker Arms, Shaft, and Push Rod Re­
placement."
G M C S E R V I C E M A N U A L
gasket.
readily accessible unless the radiator core is first
removed. The special tool typically illustrated in
figure 35 must be used to start the pulley off the
crankshaft when a retaining cone is used.
REMOVAL
a ccess to crankshaft pulley.
and use conventional wrench to remove pulley re­
taining bolt.
shown in figure 35, then turn puller screw to re­
move pulley from crankshaft.
GASOLINE ENGINES
G u id e Pins
Figure 3 4 — Installing Cylinder Head (Typical)
6. Install valve rocker arm cover, using new
CRANKSHAFT PULLEY
REPLACEMENT
On some models the crankshaft pulley is not
1. Remove radiator if necessary, to provide
2. Use impact wrench, or hold engine flywheel
3. Assem ble puller and center plug in manner
Figure 35— Rem oving Crankshaft Pulley
or Hub with Special Puller
Sec. 6A
Page 277
C ylinder H e a d
m m /
Cylinder Block
G a sk e t
Center Plug