Rocker Arm And Pushrod Replacement; Valve Adjustment - GMC G Service Manual

6A3-6 4.3 LITER V6
ROCKER ARM AND PUSHROD
REPLACEMENT
H Remove or Disconnect
1. Rocker arm cover. Refer to "Rocker Arm Cover
Replacement" in this section.
2. Rocker arm nut.
• If only the pushrod is to be replaced, back the
rocker arm nut off until the rocker arm can be
swung away from the pushrod, then pull the
pushrod out.
3. Rocker arm with ball.
4. Pushrod.
] Important
• Store used components in order so they can be reas­
\V\
sembled in the same location.
Inspect
• Rocker arms and balls at their mating surfaces.
These surfaces should be smooth and free from scor­
ing or other damage.
• 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.
H Install or Connect
1. Pushrod. Make sure the pushrod seats properly in the
hydraulic lifter.
2. Rocker arm with ball.
G O
Important
• When new rocker arms and/or balls are
installed, coat their bearing surfaces with
"Molykote" or equivalent.
3. Rocker arm nuts.
[ / | 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 torsional
damper lines up with the "0" mark on the timing tab
and the engine 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 posi­
tion. If the rocker arms move as the mark comes up to
the timing tab, the engine is in the number four 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, 5, 6.
• Intake: 1, 2, 3.
(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 in 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 four firing position. The
following valves may be adjusted:
• Exhaust: 2, 3, 4.
• Intake: 4, 5, 6.
6. Install the rocker arm cover. Refer to "Rocker Arm
Cover Replacement" in this section.
Figure 4 — Adjusting the Valves