Chevrolet 10 Series 1970 Service Manual page 338

ENGINE 6-16
Rocker Arm Cover
Removal
1. Disconnect crankcase ven tilation h ose(s) at rock er
arm co ver.
2. Rem ove a ir clean er.
3. Disconnect tem perature w ir e fro m ro ck er arm co ve r
clips.
4. On TS 50 and 60 s e r ie s , disconnect o il f il l e r tube at
bracket.
5. R em ove ro ck er arm cover.
Installation
1. Clean gasket su rfaces on cylin d er head and ro ck er
arm c o v e r with d e g re a s e r
gasket, in stall ro c k e r
specification s.
2. Connect tem peratu re
clips.
3. In stall a ir clean er.
4. Connect crankcase ventilation hoses.
V a lv e Mechanism
Removal
1. R em ove ro c k e r arm c o v e r as outlined.
2. Rem ove ro c k e r arm nuts, ro c k e r arm b alls, ro c k er
arm s and push rods.
NOTE: P la c e ro c k e r arm s, ro c k e r arm balls
and push rods in a rack so they may be r e ­
installed in the sam e location.
Installation and Adjustm ent
NOTE: W henever new
ro ck er arm b a lls a re being installed, coat b e a r­
ing surfaces of ro c k e r arm s and ro ck er arm
b alls with " M olykote,, o r its equivalent.
F ig . 1 L—V a lv e A dju stm e n t
then, using a new
arm c o v e r and torque to
w ir e at ro c k e r arm co v er
ro c k e r arm s and/or
1. In stall push rods. Be sure push rods seat in lift e r
socket.
2. Install ro ck er arm s,
arm nuts. Tighten ro ck er arm nuts until a ll lash is
elim inated.
3. Adjust va lve s when lift e r is on base c ir c le of cam ­
shaft lobe as follow s:
a. M ark distribu tor housing, with chalk, at number
one and number s ix cylin d er positions (plug w ire )
then disconnect plug w ire s at spark plugs and c o il
and rem o ve distribu tor cap and plug w ire a ssem ­
b ly (if not p reviou sly done).
b. Crank engine until distribu tor ro to r points to
number one cylin d er position and brea k er points
a re open. The follo w in g v a lve s can be adjusted
with engine in number one fir in g position.
Num ber one cy lin d e r—Exhaust and Intake
Number two cy lin d er—Intake
Num ber three cylin d er—Exhaust
Number fou r cy lin d er—Intake
Num ber fiv e c y lin d e r—Exhaust
c. Back out adjusting nut until lash is fe lt at the push
rod then turn in adjusting nut until a ll lash is
rem oved. This can be determ ined by checking
push rod side play while turning adjusting nut
(fig . 1L). When play has been rem oved, turn ad­
justing nut in one fu ll additional turn (to center
lift e r plunger).
d. Crank engine until distribu tor ro to r points to
number six position and b re a k e r points are open.
The fo llo w in g va lves can be adjusted with engine
in number six fir in g position:
Number two cylin d er—Exhaust
Number three cy lin d er—Intake
Number fou r cy lin d er—Exhaust
Number fiv e cy lin d er—Intake
Number six cylin d er—Intake and Exhaust
4. Install distribu tor cap and spark plug w ire assem bly.
5. Install ro ck er arm c o v er as outlined.
6. Adjust carbu retor idle speed and m ixture.
V a lv e Lifters
Hydraulic va lve lifte r s v e r y seldom req u ire attention.
The lifte r s are e x trem ely sim ple in design, readjust­
ments a re not n ecessary,
req u ires only that care and cleanlin ess be e x e rc is e d in
the handling of parts.
Locating Noisy Lifters
Locate a noisy va lve lift e r by using a p iece o f garden
hose approxim ately four fe e t in length. P la c e one end of
the hose near the end of each intake and exhaust va lve
with the other end of the hose to the ear. In this manner,
the sound is lo c a liz e d making it easy to determ ine which
lift e r is at fault.
Another method is to place a fin g e r on the face of the
va lve spring reta in er. If the lift e r is not functioning
p rop erly, a distinct shock w ill be fe lt when the va lve
returns to its seat.
The gen eral types of va lv e lift e r noise are as follow s:
1. H ard Rapping N oise - U sually caused by the plunger
becom ing tight in the b ore of the lift e r body to such
an extent that the return sprin g can no lon ger push
ro ck er arm b a lls and ro ck er
and s e rv ic in g of the lifte rs
CHEVROLET TRUCK SERVICE MANUAL