Chevrolet 1980 Light Duty Truck Service Manual page 432

6A 1-14 IN-LINE 6
CYLINDER HEAD ASSEM BLY
Removal
1. Remove manifold assembly as previosuly outlined.
2. Remove rocker arm cover and valve mechanism as
previously outlined.
3. Drain cooling system.
4. Remove fuel and vacuum line from retaining clips
then disconnect wires from temperature sending units.
5. Disconnect air injection hose at check valve (if so
equipped).
6. Disconnect radiator upper hose at coolant outlet
housing and battery ground strap.
7. Remove cylinder head bolts, cylinder head and
gasket. Place cylinder head on two blocks of wood to
prevent damage.
Disassembly
1. With the cylinder head removed, use tool J-8062 to
compress the valve springs and remove the valve keys.
Release the compressor tool and remove rotators or spring
caps, oil shedders springs and spring damper assemblies,
then remove oil seals and valve spring shims.
2. Remove valves from cylinder head and place them
in a rack in their proper sequence so that they can be
assembled in their original positions.
Cleaning
1. Clean all deposits from combustion chambers and
valve ports using Tool J-8089.
2. Thoroughly clean the valve guides using Tool J-
8101.
3. Clean all carbon and sludge from push rods, rocker
arms and push rod guides.
4. Clean valve stems and heads on a buffing wheel.
5. Clean carbon deposits from head gasket mating
surface.
Inspection
1. Inspect the cylinder head for cracks in the exhaust
ports, combustion chambers, or external cracks to the water
chamber.
2. Inspect the valves for burned heads, cracked faces
or damaged stems.
Excessive valve stem to bore clearance will
NOTICE:
cause excessive oil consumption and may cause valve
breakage. Insufficient clearance will result in noisy and
sticky functioning of the valve and disturb engine
smoothness.
3. Measure valve stem clearance as follows:
a. Clamp a dial indicator on one side of the cylinder
head rocker arm cover sealant rail. Locate the indicator so
that movement of the valve stem from side to side (crosswise
to the head) will cause a direct movement of the indicator
stem.
b. Drop the valve head about 1/16" (1.6mm) off the
valve seat.
of the valve from side to side using light pressure to
obtain a clearance reading.
specifications it will be necessary to ream valve guides for
oversize valves as outlined.
If clearance exceeds
Fig. 6A1-1 6-Checking Valve Spring Tension
4. Check valve spring tension with Tool J-8056 spring
tester (fig. 6A1-16). Springs should be replaced if not within
10 lbs. (44 N) of the specified load (without dampers).
5. Inspect rocker arm studs for wear or damage.
Assembly
1. Insert valves in the proper ports.
2. Set the valve spring shim, valve spring (with
damper), oil shedder and valve cap or rotator in place (fig.
6A1-17).
3. Compress the spring with Tool J-8062.
4. Install new oil seal in the lower groove of the stem,
making sure that the seal is flat and not twisted.
* * ROTATOR OKI EXHAUST VALVE
* NOT USED ON 250 CU. IN. L6
Fig. 6A1-1 7-Valve Spring Installation
LIG H T T R U C K S E R V IC E M AN U A L