Locating Noisy Lifters; Valve Lifters; Valve Adjustment; Compressing Valve Spring - Chevrolet 10 1971 Series Chassis Service Manual

are open. The following valves can be adjusted
with engine in number one firing position.
Number one cylinder—Exhaust and Intake
Number two cylinder—Intake
Number three cylinder—Exhaust
Number four cylinder—Intake
Number five cylinder—Exhaust
c. Back out adjusting nut until lash is felt at the push
rod then turn in adjusting nut until all lash is
removed. This can be determined by checking
push rod side play while turning adjusting nut
(fig. 1L). When play has been removed, turn ad­
justing nut in one full additional turn (to center
lifter plunger),
d o Crank engine until distributor rotor points to
number six position and breaker points are open.
The following valves can be adjusted with engine
in number six firing position:
Number two cylinder—Exhaust
Number three cylinder—Intake
Number four cylinder—Exhaust
Number five cylinder—Intake
Number six cylinder—Intake and Exhaust
4. Install distributor cap and spark plug wire assembly.
5. Install rocker arm cover as outlined.
6. Adjust carburetor idle speed (and mixture on 20-30
series only).

Valve Lifters

Hydraulic valve lifters very seldom require attention.
The lifters are extremely simple in design, readjust­
ments are not necessary, and servicing of the lifters
requires only that care and cleanliness be exercised in
the handling of parts.
Fig. 1 L— V a lv e Adjustment

Locating Noisy Lifters

Locate a noisy valve lifter by using a piece of garden
hose approximately four feet in length. Place one end of
the hose near the end of each intake and exhaust valve
with the other end of the hose to the ear. In this manner,
the sound is localized making it easy to determine which
lifter is at fault.
Another method is to place a finger on the face of the
valve spring retainer. If the lifter is not functioning
properly, a distinct shock will be felt when the valve
returns to its seat.
The general types of valve lifter noise are as follows:
1. Hard Rapping Noise - Usually caused by the plunger
becoming tight in the bore of the lifter body to such
an extent that the return spring can no longer push
the plunger back up to working position. Probable
causes are:
a. Excessive varnish or carbon deposit causing ab­
normal 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 leakdown rate.
b. Leaky check valve seat.
c. Improper adjustment.
3. General Noise Throughout the Valve Train - This
will, in almost all cases, 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, the 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 the
Fig. 2 L— Compressing V a lve Spring
ENGINE 6-17
10-30 CHEVROLET TRUCK SERVICE MANUAL