Chevrolet 10 Series 1967, Service Manual

Page: 367 / 605

ENGINE-ELECTRICAL 6Y-19
The timer core rotates inside a magnetic pick-up as­
sembly, which replaces the conventional breaker plate,
contact point set, and condenser assembly. The mag­
netic pick-up assembly consists of a ceramic permanent
magnet, a pole piece, and a pick-up coil. The pole piece
is a steel plate having equally spaced internal teeth, one
tooth for each cylinder of the engine.
The magnetic pick-up assembly is mounted on a plate
over the main bearing of the distributor housing. The
tim er core is made to rotate about the shaft by conven­
tional advance weights, thus providing centrifugal
advance.
MAINTENANCE AND ADJUSTMENTS
PERIODIC M A IN TEN A N C E
BREAKER POINT SYSTEM
The distributor breaker points and spark plugs are the
only ignition system components that require periodic
service. The remainder of the ignition system requires
only periodic inspection to check operation of the units,
tightness of the electrical connections, and condition of
the wiring. When checking the coil, test with a reputable
tester.
Breaker type distributors are equipped with cam lubri­
cator and should have the wick replaced at the same time
contact point set is replaced. It is not necessary to
lubricate the breaker cam when using a cam lubricator.
Do not attempt to lubricate the wick - Replace when
necessary. When installing a new wick, adjust its position
so the end of the wick just touches the lobe of the breaker
cam.
Distributor shaft lubrication is accomplished by a
reservoir of lube around the mainshaft in the distributor
body or through a hinged cap oiler on governor type units.
BREAKERLESS SYSTEM
Since there are no moving parts in the ignition pulse
amplifier unit mounted forward of the radiator bulkhead,
and the distributor shaft and bushings have permanent
type lubrication, no periodic maintenance is therefore
required for the breakerless ignition system. The dis­
tributor lower bushing is lubricated by engine oil through
a splash hole in the distributor housing, and a housing
cavity next to the upper bushing contains a supply of
lubricant which will last between overhaul periods. At
time of overhaul, the upper bushing may be lubricated
by removing the plastic seal and then adding SAE 20
oil to the packing in the cavity. A new plastic seal will
be required since the old one will be damaged during
removal.
Tachometer readings for test purposes can be made on
the primary circuit of the breakerless ignition system
in the same manner as on the conventional ignition sys­
tem, however before attempting to connect a test tachom­
eter into the primary circuit check with your instrument
supplier to insure that satisfactory readings can be ob­
tained and the breakerless system will not be damaged by
the tachometer that is to be used.
CAUTION: Never install a condenser of any
rating between the coil positive and ground. The
use of a condenser at this location for radio
suppression can damage the power transistor in
the ignition amplifier unit.
IGNITION COIL CHECK (BREAKERLESS)
The ignition coil primary can be checked for an open
condition by connecting an ohmmeter with car battery
disconnected across the two primary terminals. Primary
resistance at 75°F. should be between .35 and .55 ohm.
An infinite reading indicates the primary is open. For
the engine to run but miss at times, the primary open
may be of the intermittent type.
The coil secondary can be checked for an open by con­
necting an ohmmeter from the high tension center tower
to either primary terminal. To obtain a reliable reading,
a scale on the ohmmeter having the
2 0 , 0 0 0
ohm value
within, or nearly within, the middle third of the scale
should be used. Secondary resistance at 75°F. should be
between 8,000 and 12,500 ohms. If the reading is in­
finite, the coil secondary winding is open.
A number of different types of coil testers are avail­
able from various test equipment manufacturers. When
using these testers, follow the procedure recommended
by the tester manufacturer.
NOTE: Make sure the tester will properly
check this special coil.
SPARK PLUGS
Should be removed, inspected cleaned and regapped at
tune-up. Defective plugs should be replaced, see Servic­
ing of Units Off the Vehicle.
F ig . 3 i—Adjusting Spinner Governor
CHEVROLET TRUCK SERVICE MANUAL