TROUBLESHOOTING GM VALVE LIFTERS
LOCATING NOISY LIFTERS
Place a finger on face of valve spring retainer. If lifter is not functioning properly, a distinct shock will be felt when valve returns to its seat. General types of valve lifter noise are:
1. Hard Rapping Noise - Usually caused by plunger becoming tight in bore of lifter body to such an extent that return spring can no longer push plunger back up to working position. Probable causes are --
a. Excessive varnish or carbon deposit which
causes abnormal stickiness.
b. Galling or " pickup" between plunger and bore of lifter body, usually caused by an abrasive piece of dirt or metal wedging between plunger and lifter body.
2. Moderate Rapping Noise - Probable causes are -
a. Excessively high leak down rate.
b. Leaky check valve seat.
c. Improper adjustment.
3. General Noise Throughout Valve Train -This, in most cases, will be a definite indication of insufficient oil supply or improper adjustment.
4. Intermittent Clicking - Probable causes are --
a. A microscopic piece of dirt momentarily caught between ball seat and check valve ball.
b. In rare cases, ball itself may be out-of-round or have a flat spot.
c. Improper adjustment.
In most cases, where noise exists in one or more lifters, all lifter units should be removed, disassembled, cleaned in a solvent, reassembled and reinstalled in engine.
Place valve lifters in a rack so they may be reinstalled in same location.
When installing new rocker arms and/or rocker arm balls, coat bearing surfaces of rocker arms and rocker arm balls with engine oil supplement.
======== VALVE ADJUSTMENT - ENGINE RUNNING
ALL GM ENGINES with Hydraulic lifters
Following procedure should be completed only if "readjustment" is required.
1. Run engine until it reaches normal operating temperature.
2. With engine running at idle, back off 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. Turn nut down 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 turned down 5/8" to 1 turn from zero lash position.
NOTE: This 1 turn pre-load adjustment must be done slowly to allow lifter to adjust itself, thus preventing possible interference between inlet valve head and top of piston which might result in internal damage and/or bent push rods.
=== VALVE ADJUSTMENT -- ENGINE STOPPED
With valve cover removed, adjust valves when lifter is on low part of camshaft lobe, as follows:
a. Use remote starter switch to crank engine until distributor rotor points to No. 1 cylinder position and breaker points are open. Following valves can be adjusted with engine in No. 1 firing position.
No. 1 Cylinder- Exhaust and intake
No. 2 Cylinder -- Intake
No. 3 Cylinder -- Exhaust
No. 4 Cylinder -- Intake
No. 5 Cylinder -- Exhaust (6-cyl. Only)
b. Back out adjusting nut until lash is felt at push rod, then turn in adjusting nut until all lash is removed. This can be determined by checking push rod end play (up and down) while turning adjusting nut. (Figure 4) When play is removed, turn adjusting nut in 1 additional turn.
c. Crank engine until distributor rotor points to No. 6 position for 6-cylinder engine and No. 4 for 4-cylinder engine (and breaker points are open). Following valves can be adjusted with engine in this position:
No. 2 Cylinder -- Exhaust
No. 3 Cylinder -- Intake
No. 4 Cylinder -- Exhaust
No. 5 Cylinder -- Intake (6-Cyl. Only)
No. 6 Cylinder -- Intake and Exhaust (6-Cyl. Only)
a. Crank engine with starter or turn over in normal direction of rotation until mark on damper lines up with center "O" mark on timing tab crankcase front cover, and engine is in No. 1 firing position. This may be determined by placing fingers on No. 1 valve as mark on damper comes near "O" mark on timing mark. If valves move as mark comes up to timing tab, engine is in No. 6 firing position and should be turned over one more time to reach No. 1 position.
b. With engine in No. 1 firing position, the following valves may be adjusted.
left Hand (Standard) Rotation Engines
Exhaust -- 1-3-4-8
Intake -- 1-2-5-7
Right Hand (Opposite) Relation Engines
Exhaust -- 1-2-5-7
Intake -- 1-3-4-8
c. Back out adjusting nut until lash is felt at push rod, then turn in 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.
Hydraulic lifters now can be adjusted by tightening adjustment nut 1 additional turn to place plunger in center of its travel.
d. Crank engine one revolution until pointer "O" mark and torsion damper mark are again in alignment. This is No. 6 firing position. The following valves may be adjusted as previously outlined
Left Hand (Standard) Rotation Engines
Exhaust -- 2-5-6-7
Intake -- 3-4-6-8
Right Hand (Opposite) Rotation Engines
Exhaust -- 3-4-6-8
Intake -- 2-5-6-7