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Section l-Manifold Replacement
25
Before reassembling and installing the
manifolds,
make sure all gasket surfaces are free from old gasket
material and projections that may affect
sealing.
To install the
manifolds,
fasten them together and
tighten the nuts to 30-35 foot-pounds torque.
Place
new
manifold gaskets
(fig.
7) on the block and install the
manifolds. Tighten the manifold retaining nuts
to
25-
30 foot-pounds
torque.
Start at the center
a nd
work
toward the
e
nds to avoid manifold distortion when
tightening the
nuts.
Connect the muffler inlet pipe. Install the manifold
air baffle assembly and secure it to the cylinder head
and
engine
support bracket. Install the
carburetor.
Con-
nect
the
windshield wiper hose, fuel
line,
choke wire,
distributor vacuum line, and air cleaner flexible tube.
Lower the engine compartment front cover and install
the engine
compa
rtment
rea
r
cover.
2. CYLINDER HEAD REPLACEMENT
Cylinder heads are cast from the same high grade
iron as is used for the cylinder block. Expansion and
contraction due to temperature variations
is the
same
for both head and block lessening the possibility of
cylinder head distortion.
NOTE: The lHA-6050 cylinder head i. interchange·
able
with either
the
7HA·6050 or
the
OHA·6050
cylinder head.
Cylinder heads must be repl aced when
cracks
develop
or distortion prevents adequate sealing at the gasket
surface.
Replacement procedures are covered under headings
"a. Conventional
Truck,"
"b.
Cab-Over-Engine." a
nd
"c. P arcel Delivery."
a. Conventional Truck.
Drain the cooling system. Remove the air
clea ner.
Disconnect the upper radiator hose at the cylinder head.
Disconnect the cylinder head temperature unit sending
wire.
Remove the screw from the distributor
vac
uum
line clamp on the forward left corner of the cylinder
head. Disconnect the ignition wires from the spark plugs
and remove the
plugs.
Remove the two screws from
the coil bracket and let the bracket hang from the dis-
tributor. Disconnect the heater hose. Remove the screw
from the manifold air baffle assembly on the right-hand
side of the cylinder
head.
Remove the cylinder head
bolts, then remove the cylinder head.
Before installing a cylinder head, clean the carbon
deposits from the combustion chambers and check to
see that all water passages are open. Gasket surfaces
Fig.
IO-Cylinder Head Gasket 'n.talfatlon
must be free of old gasket material and projections at
bolt holes that may affect
sealing.
Install
a new
cylinder head gasket (fig. 10) with the
cut off corner at the left front corner of the block.
NOTE: If
the
ga.ket i. installed
imprope rly,
water
will leak
exte
rnally at the left rear corner of the
engine
between cylinder head and block. Do not
enlarge
any gasket holes or overheating oj the rear
cylinders m.ay r esult.
Place the cylinder head in position on the block,
being careful not to damage the
gasket.
Before
insta
ll-
ing the cylinder head
bolts,
coat the bolt threads with
a light coat of water resistant
sealer.
Insert the cylinder
head bolts and tighten them to 65-70 foot-pounds
torque in the sequence shown in fig. 11. Fasten the
manifold air baffle assembly to the cylinder head. Con-
nect the heater
hose.
Fasten the distributor vacuum
line clamp to the cylinder
head.
Connect the tempera-
ture unit sending wire. Install the spark plugs. Torque
the plugs to 24-30 foot-pounds. Position the coil bracket
and install the two holding screws. Connect the ignition
secondary wires to the spark plugs. Connect the radiator
hose. Fill the cooling system according to the prevail-
ing temperature. Operate the engine for five minutes,
stop the engine, and check the coolant level in the
radiator.
b. Cab.Over.Engine.
Drain the cooling
system.
Disconnect the upper
radiator hose at the cylinder head. Remove the engine
compartment
cover.
Disconnect the cylinder head tem-
perature sending unit wire. Remove the screw from
1132
Fig
.
II-Cylinder Head Bolt Tightening Sequ.n,.
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