Chevrolet 70 1969 Series, Руководство по ремонту

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ENGINE ELECTRICAL 6Y-14
IN S T A L L A T IO N
N O T E : The service replacement contact set
has the breaker lever spring and the point align­
ment preadjusted. Only the dwell angle requires
adjustment after replacement.
1. Place new contact set assembly on breaker
plate and install attaching screw.
C A U T IO N : Carefully wipe protective film from
contact set prior to installation.
N O T E : Pilot on contact set must engage match­
ing hole in breaker plate.
2. Connect primary lead and condenser lead
to terminals (fig. 4). Lead clips must be assem­
bled "back-to-back." Push clip nearest the contact
lever down between the spring and locator; then
push the remaining clip down between the first
clip and locator. Do not push on the spring.
3. Apply a slight trace of petroleum jelly to
the breaker cam and a few drops of SAE #20 oil
on top of the shaft.
4. Check and adjust points for proper align­
ment and breaker arm spring for proper tension
(fig. 5). Use an alignment tool to bend stationary
contact support if points need alignment.
N O T E : The contact point pressure must fall
within specified limits. Weak tension will cause
chatter resulting in arcing and burning of the points
and an ignition miss at high speed, while excess­
ive tension will cause undue wear of the contact
points, cam and rubbing block. Breaker arm spring
tension should be 19-23 ounces. The contact point
pressure should be checked with a spring gauge.
The scale should be hooked to the breaker lever
and the pull exerted at 90 degrees to the breaiker
lever as shown in figure 5. The reading should be
taken just as the points separate. The pressure
can be adjusted by bending the breaker lever spring.
If pressure is excessive, it can be decreased by
pinching the spring carefully. To increase pres­
sure, the lever must be removed from the dis­
tributor so the spring can be bent away from the
lever. Avoid excessive spring distortion.
5. Set point opening to dimension listed in
"Specifications " at end of this section.
6. Install rotor, then position and secure dis­
tributor cap to housing.
SETTING DWELL ANGLE
The point opening of new points can be checked
with a feeler gauge, but the use of a feeler gauge
on rough or uncleaned used points is not recom­
mended since accurate mechanical gauging cannot
be done on such points.
rapidly. Points with excessive separation tend to
cause a weak spark at high speed. Proper point
setting for these engines are listed in "Specifica­
tions” at end of this section.
New points should be set to the larger opening
as the rubbing block will wear down slightly while
seating to the cam. Contact points should be clean­
ed before adjusting if they have been in service.
C O N T A C T POINT OPEN IN G A D J U S T M E N T
1. Release distributor cap hold-down screws,
remove cap and place it out of work area.
2. Check alignment of contact points. Do not
bend the breaker lever. Do not attempt to align
used points; replace them where serious mis­
alignment is observed.
3. Turn the distributor shaft until the breaker
arm rubbing block is on the high point of the cam
lobe. This will provide maximum point opening.
4. Loosen the contact support lock screw.
5. Use a screwdriver to move point support to
obtain a 0.019" opening for new points (0.016"
opening for used points) (fig. 6).
6. Tighten the contact support lock screw and
recheck the point opening.
7. After checking and adjusting the contact
point opening to specifications, the cam angle or
dwell should be checked with a dwell meter, if
such equipment is available (see "Specifications"
at end of section for proper dwell angle).
N O T E : D IS C O N N E C T A N D PLU G V A C U U M
LIN E W H E N C H E C K IN G . If the cam angle is less
than the specified minimum, check for defective
or misaligned contact points or worn distributor
cam lobes. The variation in cam angle readings
between idle speed and 1750 engine rpm should not
exceed 3°. Excessive variation in this speed range
indicates wear in the distributor.
-f
Contact points must be set to the proper open­
ing. Points set too close may tend to burn and pit
Figure 5— Checking Breaker Arm Spring Tension
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L