Chevrolet Light Duty Truck 1973 Service Manual page 345

Fig. 14—Setting Point Dwell (Typical V8)
ADJUST IDLE SPEED (FIG. 16)
Emission system requirements necessitate the division of
the Series 10-30 trucks into two groups as follows:
a. Light Duty Emission Vehicles - Includes all 10
Series; C-K20 Suburban Models; All G20 Series
and G30 Passenger Models.
b. Heavy Duty Emission Vehicles - Includes all C-K-
P20 Series (Except C-K20 Suburban Models); all
C-P30 Series and all G30 Series (Except Passenger
Models).
NOTE: Idle speed will increase as new
engines loosen up during the first few
hundred miles of operation. Idle speed should
be reset during tune-up as specified in the
following procedures.
With engine running at operating temperature, air
cleaner installed, choke valve in fully open position, air
conditioning "off", parking brake on and drive wheels
blocked - adjust idle speed as follows (See "Tune-up"
Decal Figure 17.):
NOTE: All carburetors are equipped with
idle mixture limiter caps (fig. 16), the idle
mixture is preset and "locked in" by these
caps - no attempt should be made to adjust
mixture. Do not remove mixture screw caps.
• 250 Cu. In. (Single-Barrel Carburetor)
On 250 cu. in. Light-Duty vehicles, disconnect "Fuel
Tank" line from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
Adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain:
700 rpm on all Heavy-Duty Vehicles and all Light-
Duty vehicles equipped with manual transmission
(in neutral).
W INDOW
"H E X " TYPE
W RENCH
SCREW
Fig. 15—Ignition Timing Marks
600 rpm on Light-Duty vehicles equipped with
automatic transmissions (in "Park").
NOTE: Light-Duty vehicles are equipped
with the carburetor mounted CEC solenoid
(fig. 16). DO NOT ADJUST THE CEC
SOLENOID SCREW.
If the CEC solenoid screw ( f i g . 16)
CAUTIO N:
i s used t o s e t engine i d l e or if the solenoid i s
adjusted out of l i m i t s as specified i n Section
6M, a decrease i n engine braking may r e s u l t .
Place transmission in "park" or netural and adjust
carburetor fast idle speed to obtain 1800 rpm with cam
follower on top step of cam.
Reconnect "Fuel Tank" line to vapor canister and
reconnect distributor spark advance hose.
• 292 Cu. In. (Single-Barrel Carburetor)
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
Adjust Idle Stop Solenoid (turn solenoid body, using hex
nut) to obtain:
600 rpm on vehicles equipped with Air Injection
Reactor System (State of California Vehicles).
700 rpm on vehicles not equipped with Air Injection
Reactor System.
Reconnect distributor spark advance hose.
• 307 Cu. In. (Two-Barrel Carburetor)
On Light-Duty vehicles, disconnect "Fuel Tank" line
from Evaporation Emission vapor canister.
Disconnect the distributor spark advance hose and plug
the vacuum source opening.
ENGINE 6-9
LIGHT DUTY TRUCK SERVICE MANUAL