Valve Adjustment; Valve Stem Seal And Valve Spring Replacement - GMC G Service Manual

• Rocker arm areas which contact the valve stems, and
the sockets which contact the pushrods. These areas
should be smooth and free of damage and wear.
• Pushrods for bending. Roll the pushrod on a flat sur­
face to determine if it is bent. Replace if necessary.
• Ends of the pushrods for scoring or roughness.
Install or Connect
E
Pushrod. Make sure the pushrod seats properly in the
hydraulic lifter.
Rocker arm with ball.
U Important
• When new rocker arms and/or balls are
installed, coat their bearing surfaces with
"Molykote" (or equivalent).
3. Rocker arm nut.
Adjust
• Valves. Refer to "Valve Adjustment" in this
section.
4. Rocker arm cover. Refer to "Rocker Arm Cover
Replacement" in this section.

VALVE ADJUSTMENT

1. Remove the rocker arm cover. Refer to "Rocker Arm
Cover Replacement" in this section.
2. Crank the engine until the mark on the vibration
damper lines up with the "0" mark on the timing tab,
and the engine is in the number one firing position.
This may be determined by placing fingers on the
number one valve as the mark on the damper comes
near the "0" mark on the timing tab. If the rocker arms
are not moving, the engine is in the number one firing
position. If the rocker arms move as the mark comes
up to the timing tab, the engine is in the number six
firing position and should be turned over one more
time to reach the number one position.
3. With the engine in the number one firing position as
determined above, the following valves may be
adjusted:
• Exhaust: 1, 3, 4, 8
• Intake: 1, 2, 5, 7
(Even-numbered cylinders are in the right bank; odd-
numbered cylinders are in the left bank, when viewed
from the rear of the engine.)
4. Back out the adjusting nut until lash is felt at the
pushrod, then turn in the adjusting nut until all lash is
removed. This can be determined by rotating the
pushrod while turning the adjusting nut (figure 4).
When the play has been removed, turn the adjusting
nut inward one full additional turn (to center the lifter
plunger).
5. Crank the engine one revolution until the timing tab
"0" mark and vibration damper mark are again in
alignment. This is the number six firing position; the
following valves may be adjusted:
SMALL BLOCK 6A4-7
• Exhaust: 2, 5, 6, 7
• Intake: 3, 4, 6, 8
6. Install the rocker arm cover. Refer to "Rocker Arm
Cover Replacement" in this section.
VALVE STEM SEAL AND VALVE
SPRING REPLACEMENT
E
Remove or Disconnect (Figures 5 and 6)
Tools Required:
J 23590 Air Adapter.
J 5892-B Valve Spring Compressor.
1. Rocker arm cover. Refer to "Rocker Arm Cover
Replacement" in this section.
2. Rocker arms. Refer to "Rocker Arm and Pushrod
Replacement" in this section.
3. Spark plugs.
4. Valve keepers (20).
• Install J 23590 into the spark plug hole
(figure 6).
• Apply compressed air to hold the valves in
place.
• Install a rocker arm nut.
• Use J 5892-B to compress the valve spring
(figure 6).
• Remove the valve keepers.
• Carefully release the spring tension. Remove
J 5892-B.
5. Cap (21) or rotator (28), shield (22), and spring (26)
with damper (25).
6. O-ring seal (23).
7. Seal (24) (intake valve only).