Valve Mechanism; Removal; Installation And Adjustment; Valve Lifters - Chevrolet 1974 Light Duty Truck Service Manual

4. Connect crankcase ventilation hoses.
5. Install air injection hose.

Valve Mechanism

Removal

1. Remove rocker arm cover as outlined.
2. Remove rocker arm nuts, rocker arm balls, rocker
arms and push rods.
NOTE: Place rocker arms, rocker arm balls
and push rods in a rack so that they may be
reinstalled in the same location.

Installation and Adjustment

NOTE: Whenever new rocker arms and/or
rocker arm balls are being installed, coat
bearing surfaces of rocker arms and rocker
arm balls with "Molykote" or its equivalent.
1. Install push rods. Be sure push rods seat in lifter
socket.
2. Install rocker arms, rocker arm balls and rocker
arm nuts. Tighten rocker arm nuts until all lash is
eliminated.
3. Adjust valves when lifter is on base circle of
camshaft lobe as follows:
a. Mark distributor housing, with chalk, at number
one and number six cylinder positions (plug
wire) then disconnect plug wires at spark plugs
and coil and remove distributor cap and plug
wire assembly (if not previously done).
b. Crank engine until distributor rotor points to
number one cylinder position and breaker
points 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. 6L). When play has been removed, turn
adjusting nut in one full additional turn (to
center lifter plunger).
d. 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
Num ber 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.

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.

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:
Fig. 6L— Valve Adjustment
ENGINE 6-27
LIGHT DUTY TRUCK SERVICE MANUAL