GMC 1976 ZEO 6083 Maintenance Manual page 304

2 . Remove valve keys by compressing valve
spring with a tool J-5892-1 .
3 . Remove valve spring rotators or retainers and
springs.
4. Remove oil seals from valve stems.
5 . Remove valves . Keep valves separated so they
can be installed in their original locations . See Figure
29 .
INSTALLATION
Figure 29-Valve Location
1 . Install valves in their respective guides .
2. Install new oil seals over valve stem, using Tool
J-24725 . See Figure 30 .
Position seals down as far as possible on valve
stem . The seals will correctly position themselves
when the engine is started.
Figure 30-Valve Seal Installation
ENGINE 6A- 39
NOTE : Inspect seal for cracks after installation .
3 . Position valve springs over valve stems.
4. Install valve rotators then compress springs
with a tool J-5892-1 and install valve stem keys .
5. Check valve springs and keys to be sure they
are properly seated .
6. Set spark plug gap. Lubricate plug threads
with one drop of engine oil and re-install plugs.
Torque to 35 ft . lbs. for vehicles equipped with
breaker point ignition systems, and 25 ft . lbs. for high
energy ignition systems.
Reconditioning Valves
When reconditioning valves and valve seats,
clean carbon from cylinder heads and valves using
care not of gouge or scratch machined surfaces . A
soft wire brush is suitable for this purpose. Whenever
valves are replaced or new valves installed, the valve
seats must be reconditioned.
Figure 31 shows the relation of valve angle and
valve seat angle. Arc "A" should be 44° on the intake
valve and 30° on the exhaust valve. Arc "B" should
be 45° on the intake valve seat and 31° on the exhaust
valve seat .
Narrow the valve seats to the specified width.
NOTE : This operation is done by grinding the
portside with a 30° stone to lower the seat and
a 60° stone to raise the seat .
See "Engine Specification" Chart for valve seat
width.
Figure 31-Relation of Valve and Seat Angles