Chevrolet 10 Series 1968, Service Manual

Page: 396 / 713

ENGINE FUEL 6M-3
Rochester M
• Float
• Idle Vent
• Unloader
Rochester 2 G
• Float
• Accelerator Pump
• Idle Vent
• Choke Rod (Fast Idle)
F ig . 5 C —Remote Choke Adjustment
5. Install air cleaner.
Float Adjustment (Holley 4 1 5 0 G )
1. Remove air cleaner then remove the fuel level sight
plugs.
2. With parking brake on, and transmission in neutral,
start the engine and allow it to idle.
3. With the car on a level surface, the fuel level should
be on a level with the threads at the bottom of the
sight plug port (plus or minus 1/32 inch).
NOTE:
No float drop adjustment is required
on this carburetor.
4. If necessary to adjust (either or both bowls), loosen
inlet needle lock screw and turn the adjusting nut
clockwise to lower or counter-clockwise to raise
fuel level, then tighten lock screw.
NOTE: 1/6 turn of adjusting nut equals ap­
proximately 1/16" fuel level change.
5. Allow a minute for fuel level to stabilize then re-
check the level at sight plug.
6. Readjust, if necessary, until proper level is obtained,
then install sight plug and air cleaner.
NOTE:
To assure proper secondary float level
setting it is advisable to accelerate primary
throttles slightly and hand operate secondary
throttle. This assures a stabilized secondary
fuel level.
Additional Adjustments
The following adjustments may be made without remov­
ing the carburetor from the engine. For procedure refer
to Section 6M of the Overhaul Manual under the carbure­
tor being serviced.
Rochester 4 M V
•
Float
• Accelerator Pump
• Idle Vent
• A ir Valve
• Choke Rod
• Choke Vacuum Break
• Choke Unloader
• Secondary Throttle Lockout
• Secondary Opening
• Secondary Closing
H o lle y 4 1 5 0 G
•
Float
• Idle Vent
• Choke Rod
• Accelerator Pump
Rem oval
Flooding, stumble on acceleration and other perform­
ance complaints are, in many instances, caused by the
presence of dirt, water, or other foreign matter in the
carburetor. To aid in diagnosing the cause of the com­
plaint, the carburetor should be carefully removed from
the engine without draining the fuel from the bowl. The
contents of the fuel bowl may then be examined for con­
tamination as the carburetor is disassembled.
1. Remove air cleaner and gasket.
2. Disconnect fuel and vacuum lines from carburetor.
3. Disconnect choke cable.
4. Disconnect accelerator linkage.
5. If equipped with Automatic transmission, disconnect
TV linkage.
6 Remove carburetor attaching nuts and remove
carburetor.
Test Before Installation
It is good shop practice to fill the carburetor bowl be­
fore installing the carburetor. This reduces the strain
on the starting motor and battery and reduces the possi­
bility of backfiring while attempting to start the engine.
A fuel pump clamped to the bench, a small supply of fuel
and the necessary fittings enable the carburetor to be
filled and the operation of the float and intake needle and
seat to be checked. Operate the throttle several times
and check the discharge from the pump jets before in­
stalling the carburetor.
Installation
1. Be certain throttle body and intake manifold sealing
surfaces are clean.
2. Install new carburetor to manifold flange gasket (if
required).
3. Install carburetor over manifold studs.
4. Start vacuum and fuel lines at carburetor.
5. Install attaching nuts and tighten securely.
6. Tighten fuel and vacuum lines.
CHEVROLET TRUCK SERVICE MANUAL