Chevrolet 10 Series 1970, Руководство по обслуживанию

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ENGINE 6-8
W IN D O W
"H E X ” TYPE
ADJUSTING
SCREW
F ig . 14—S e ttin g P oint D w e ll
V8 ENGINES
• With engine running at idle, ra is e the adjustment
s crew window and in sert an A llen wrench in the
socket o f the adjusting screw (fig. 14).
• Turn the adjusting screw as requ ired until a dwell
reading o f 30° is obtained. A 2° variation is a llo w ­
able fo r w ear.
• C lose a cc e s s c o v e r fu lly to preven t the entry of
d irt into the d istribu tor.
NOTE:
If a dw ell m eter is not availab le, turn
adjusting screw clock w ise until engine starts to
m is fir e , then turn screw on e-h alf turn in the
opposite d irection to com plete adjustment.
IN L IN E ENGINES
• Rem ove d istrib u tor cap and rech eck point setting.
If dw ell is s till not within sp ecification s check the
distributor as outlined in Section 6Y.
Check Dwell Variation
Slowly a c c e le ra te engine to 1500 rpm and note dwell
reading. Return engine to idle and note dw ell reading.
If dw ell variation exceeds sp ecification s, check fo r worn
distribu tor shaft, worn distributor shaft bushing o r loose
b rea k er plate.
Check and Adjust Ignition Timing (Fig. 15)
1. Disconnect the distribu tor spark advance hose and
plug the vacuum source opening.
2. Start engine and run at idle speed (See tune up chart
in Specification section.
3. A im tim ing light at tim ing tab.
NOTE:
The m arkings on the tabs a re in 2°
increm ents (the grea test number o f m arkings on
the " A " side o f the “ O” ). The " O ” marking
is TD C and a ll BTD C settings fa ll on the " A "
(advance) side o f
“ O” .
4. Adjust the tim ing by loosening the distribu tor clam p
and rotating the distribu tor body as requ ired, then
tighten the clam p and recheck.tim ing.
5. Stop engine and rem ove tim ing light and reconnect
the spark advance hose.
Adjust Idle Speed and Mixture
NOTE:
On v eh icles equipped with E vaporative
E m ission (R PO NA9) disconnect " F U E L T A N K ’ '
line from vapor can ister. (See Section 8 fo r
E vaporative Em ission System .) A fte r tuning en­
gine, reconnect " F U E L T A N K " line to vapor
can ister.
1. W ith engine running at operating tem perature (choke
v a lve and, i f applicable, a ir clea n er damper door
fully open) a ir conditioning o ff, and parking brake on -
adjust idle speed and m ixture as follow s (See "T u n e -
U p " D ecal F ig. 16):
L6 ENGINES
• 10 S e ries
Disconnect and plug distribu tor vacuum line.
Turn m ixture screw in until ligh tly contacting seat,
then back screw out four turns.
Adjust solenoid screw to obtain 800 rpm with
manual tran sm ission in neutral; 630 rpm with
automatic transm ission in d riv e (fig . 17).
Adjust m ixture screw in to obtain 750 rpm with
manual tran sm ission in neutral; 600 rpm with
F ig . 15— Ig n itio n Tuning M arks
F ig . 16—T u n e -U p D ecal
CHEVROLET TRUCK SERVICE MANUAL