Hydraulic lifters can be adjusted by tightening adjustment nut an additional 3/4-turn.
Engine Not Running
With valve cover removed, adjust valves when lifter is on low part of camshaft lobe, as
follows:
1. Crank engine with starter or turn over in normal direction of rotation until mark on
torsional damper lines up with center “0” mark on timing tab, and engine is in No. 1 firing
position. This may be determined by placing fingers on No. 1 valve as mark. If valves
move as mark comes up to timing tab, engine is in No.4 firing position and should be
turned over one more time to reach No. 1 position.
2. With engine in No. 1 firing position as determined above, the following valves may be
adjusted:
• No. 1 Cylinder - Exhaust and Intake
• No. 2 Cylinder - Intake
• No. 3 Cylinder - Exhaust
• No. 4 Cylinder - Intake
3. Loosen adjusting nut until lash is felt at push rod, then tighten adjusting nut until all lash
is removed. This can be determined by moving push rod up and down while turning
adjusting nut until all play is removed.
72300
4. Hydraulic lifters can be adjusted by tightening adjustment nut an additional 3/4-turn.
Valve lash should be checked after engine has run and reached operating temperature.
5. Crank engine one revolution until pointer “0” mark and torsional damper mark are again
Valve lash should be checked after engine has run and reached operating temperature.
5. Crank engine one revolution until pointer “0” mark and torsional damper mark are again
in alignment. This is No. 4 firing position. With engine in this position, the following valves
may be adjusted:
• No. 2 Cylinder - Exhaust
• No. 3 Cylinder - Intake
• No. 4 Cylinder - Exhaust
6. Repeat steps 3-4 to adjust other valves.
7. Install Distributor cap, spark plug wires and coil lead.
8. Install rocker arm cover; torque to 40 lb-in. (4.5 Nm).
Engine Running
Following procedure should be completed only if readjustment is required.
1. Run engine until it reaches normal operating temperature, then remove valve cover.
2. With engine running at idle, loosen valve rocker arm nut until valve rocker arm starts to
clatter.
3. Turn rocker arm nut down slowly until clatter just stops. This is zero lash position.
4. Tighten nut 1/4 additional turn and pause 10 seconds until engine runs smoothly. Repeat
additional 1/4 turns, pausing 10 seconds each time, until nut has been tightened 3/4 turn
from zero lash position.
181 CID (3.0L) 4 CYLINDER GM ENGINE SERVICE MANUAL NUMBER 26
Page 3A-20 90-861329--1 MARCH 1999
IMPORTANT: The following preload adjustment must be done slowly to allow lifter to
adjust itself, thus preventing possibility of the valve head contacting the top of
piston, which may result in internal damage and/or bent push rods.
5. Repeat Steps 2-4 to adjust other valves.
6. Install rocker arm cover, torque to 40 lb-in. (4.5 Nm).
7. Adjust carburetor idle mixture and idle speed. Check for leaks.
