Chevrolet 10 Series 1970, Service Manual

Page: 339 / 671

ENGINE 6-17
the plunger back up to w orking position. P robable
causes are:
a. E x c essive varn ish o r carbon deposit causing ab­
norm al stickiness.
b. G alling o r “ pickup” between plunger and b o re of
lift e r body, usually caused by an a b rasive piece
of d irt o r m etal wedging between plunger and
lift e r body.
2. M oderate Rapping N oise - P robable causes are:
a. E x c e s s iv e ly high leakdown rate.
b. Leaky check va lve seat.
c. Im p rop er adjustment.
3. G en eral N o ise Throughout the V a lve T ra in - This
w ill, in alm ost a ll cases, be a definite indication of
in su fficient o il supply, o r im p ro p er adjustment.
4. Interm ittent C lickin g - Prob ab le causes are:
a. A m ic ro sco p ic p iece of d irt m om entarily caught
between b all seat and check va lve ball.
b. In ra re cases, the b all its e lf may be out-of-round
o r have a fla t spot.
c. Im p rop er adjustment.
In m ost cases, w here noise exists in one o r m ore
lift e r s , a ll lift e r units should be rem oved, disassem bled,
cleaned in a solvent, reassem bled, and rein sta lled in the
engine. If dirt, varnish, carbon, etc. is shown to exist in
one unit, it m ore than lik e ly exists in a ll the units, thus
it would only be a m atter of tim e b e fo re all lifte r s caused
trouble.
Removal
1. R em ove v a lv e m echanism as outlined.
2. M ark distribu tor housing, with chalk, at number one
and number six cylin d er position (plug w ir e ) then
disconnect plug w ire s at spark plugs and c o il and
rem ove d istrib u tor cap and plug w ire assem bly.
3. Crank engine until d istrib u tor ro to r points to number
one position, then disconnect distribu tor p rim a ry
lead at c o il and rem o ve distributor.
4. R em ove push rod c o v e rs (d isca rd gaskets).
5. R em ove va lve lifte r s .
NOTE: P la c e v a lv e lift e r s in a rack so they
m ay be rein sta lled in the sam e location.
Installation
1. In sta ll v a lv e lifte r s .
NOTE: W henever new va lve lifte r s are being
in stalled, polish lift e r fe e t with #600 wet/dry
e m ery paper and coat foot of v a lv e lift e r s with
"M o ly k o te ” o r its equivalent.
2. In stall push rod co vers, using new gaskets, and
torque to specification s.
3. In stall distribu tor, positioning ro to r to number one
cylin d er position, then connect p rim a ry lead at coil.
4. In stall and adjust va lve m echanism as outlined.
5. Adjust ignition tim ing and carb u retor id le speed and
m ixture.
V a lv e Stem O il Seal a n d /o r V a lv e Spring
Replacem ent
1. R em ove ro ck er arm co v e r as outlined.
2. R em ove spark plug, ro c k e r arm and push rod on the
cylin d e r(s ) to be s erviced .
3. Apply com pressed a ir to the spark plug hole to hold
the va lv e s in place.
NOTE: A tool to apply a ir to the cylin d er is
available through lo c a l jobbers o r m ay be manu­
factured. In manufacturing this to o l a AC -46N
spark plug o r its equivalent is recom m ended.
This w ill make the tool u n iversal fo r all C h evro­
let engines. C h isel the spark plug as shown, then
d rive the p o rcela in out of the plug by tapping the
center e le ctro d e against a hard block. Using a
3/8" pipe tap, cut threads in the rem aining p o r­
tion of the spark plug and assem ble as shown
(fig . 2L).
4. Using T o o l J-5892 to com press the v a lv e spring,
rem ove the v a lv e locks, va lve cap (o r ro ta to r) va lve
shield and va lv e sp rin g and damper (fig . 3L).
5. R em ove the va lv e stem o il seal.
6. T o rep lace, set the va lve spring and dam per, va lve
sh ield and va lve cap (o r rota tor) in place. The close
co iled end of the spring is in stalled against the c y l­
inder head. C om press the spring with T o o l J-5892
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F ig . 2 L —A i r A d a p te r T ool F ig . 3 L—Compressing V a lv e Spring
CHEVROLET TRUCK SERVICE MANUAL