Chevrolet 1980 Light Duty Truck Service Manual page 467

Fig. 6A4-1 7--Assembling Hydraulic Lifter
3. Remove exhaust manifolds as previously outlined.
4. Drain cylinder block of coolant.
5. If vehicle is equipped with A/C, remove A/C
compressor and forward mounting bracket. Lay unit aside.
6. Remove valve push rods as previously outlined.
7. Remove cylinder head bolts, cylinder head and
gasket. Place cylinder head on two blocks of wood to
prevent damage.
Disassembly
1. With cylinder head removed, remove valve rocker
arm nuts, balls and rocker arms (if not previously done).
2. Using Tool J-8062, compress the valve springs (fig.
6A4-18) and remove valve keys. Release the compressor
tool and remove rotators or spring caps, oil shedders,
springs and spring damper, then remove oil seals and valve
Fig. 6 A 4 -1 8 - C o m p r e s s in g Va lve Spring
Fig. 6A4-19--Cleaning Combustion Chambers
spring shims.
3. 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 carbon from combustion chambers and
valve ports using Tool J-8089 (fig. 6A4-19).
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
coolant 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 (fig. 6A4-20) as
follows:
a. Clamp a dial indicator on one side of the cylinder
head rocker arm cover gasket rail.
b. 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. The indicator stem
must contact the side of the valve stem just above the valve
guide.
c. Drop the valve head about 1/16" (1.6mm) off the
valve seat.
from side to side using light pressure to obtain a
clearance reading. If clearance exceeds specifications, it will
be necessary to ream valve guides for oversize valves as
outlined.
S M ALL BLOCK 6A 4-15
LIG H T TR U CK SER V IC E M AN UAL