Chevrolet Full-size Cars 1968-1978 Repair Guide

Carburetors

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REMOVAL & INSTALLATION





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Fig. Fig. 1 Remove the air cleaner housing by disconnecting the hot air pipe ...



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Fig. Fig. 2 ... and the fresh air inlet hose



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Fig. Fig. 3 Disconnect the fuel line (A) and the heated air-to-choke housing line (B)



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Fig. Fig. 4 Label and remove all vacuum lines connected to the carburetor. Unhook the throttle linkage ...



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Fig. Fig. 5 ... and the transmission detent cable (if equipped with an automatic transmission)



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Fig. Fig. 6 Disconnect the power brake booster vacuum line from the carburetor



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Fig. Fig. 7 Unplug the electrical connector from the idle stop solenoid (if equipped)



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Fig. Fig. 8 Remove the carburetor attaching bolts and lift the carburetor off of the intake. Discard the old gasket



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Fig. Fig. 9 Stuff rags into the intake openings to keep any debris out of the engine

  1. Disconnect the negative battery cable. Remove the air cleaner and its gasket.
  2.  
  3. Disconnect the fuel and vacuum lines from the carburetor. As required, disconnect the PCV line at the base of the carburetor.
  4.  
  5. Disconnect the choke coil rod, heated air line tube, or electrical connector.
  6.  
  7. If equipped, remove the cruise control. Disconnect the throttle linkage.
  8.  
  9. On automatic transmission equipped vehicles, disconnect the throttle valve linkage as required.
  10.  
  11. If CEC equipped, remove the CEC valve vacuum hose and electrical connector. Disconnect the EGR line, if so equipped.
  12.  
  13. Remove the idle stop solenoid, if equipped.
  14.  
  15. Remove the carburetor attaching nuts and/or bolts, gasket or insulator, and remove the carburetor.
  16.  

To install:

  1. Position the carburetor on the intake manifold, using a new base gasket.
  2.  
  3. Install the carburetor retaining bolts. Connect the fuel line.
  4.  
  5. Connect the choke assembly. Connect the required linkage.
  6.  
  7. Connect the idle stop solenoid, the cruise control linkage and the CEC vacuum valve, as required.
  8.  
  9. Install the carburetor air cleaner assembly. Connect the negative battery cable.
  10.  
  11. Start the engine. Adjust the carburetor air/fuel mixture, if possible. Adjust the idle speed, as required. Roadtest the vehicle.
  12.  

IDENTIFICATION





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Fig. Fig. 10 Carburetor identification number location-all models

Carburetor identification numbers will generally be found in the following locations:



MV, ME: Stamped on the vertical portion of the float bowl, adjacent to the fuel inlet nut.
 
GV, GC: Stamped on the flat section of the float bowl next to the fuel inlet nut.
 
E2SE, 2SE: Stamped on the vertical surface of the float bowl adjacent to the vacuum tube.
 
M2MC: Stamped on the vertical surface of the left rear corner of the float bowl.
 
E4ME, 4MV, M4MC, M4ME: Stamped on the vertical section of the float bowl, near the secondary throttle lever.
 

OVERHAUL



All Types

Efficient carburetion depends greatly on careful cleaning and inspection during overhaul, since dirt, gum, water, or varnish in or on the carburetor parts are often responsible for poor performance.

Overhaul your carburetor in a clean, dust free area. Carefully disassemble the carburetor, referring often to the exploded views and directions packaged with the rebuilding kit. Keep similar and look-alike parts segregated during disassembly and cleaning to avoid accidental interchange during assembly. Make a note of all jet sizes.

When the carburetor is disassembled, wash all parts (except diaphragms, electric choke units, pump plunger, and any other plastic, leather, fiber, or rubber parts) in clean carburetor solvent. Do not leave parts in the solvent any longer than is necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving these parts unfit for service. Rinse all parts in clean solvent and blow them dry with compressed air or allow them to air dry. Wipe clean all cork, plastic, leather, and fiber parts with clean, lint-free cloth.

Blow out all passages and jets with compressed air and be sure that there is no restrictions or blockages. Never use wire or similar tools to clean jets, fuel passages, or air bleeds. Clean all jets and valves separately to avoid accidental interchange.

Check all parts for wear or damage. If wear or damage is found, replaced the defective parts. Especially check the following:

  1. Check the float needle and seat for wear. If wear is found, replace the complete assembly.
  2.  
  3. Check the float hinge pin for wear and the float(s) for dents or distortion. Replace the float if fuel has leaked into it.
  4.  
  5. Check the throttle and choke shaft bores for wear or an out-of-round condition. Damage or wear to the throttle arm, shaft, or shaft bore will often require replacement of the throttle body. These parts require a close tolerance of fit; wear may allow air leakage, which could affect starting and idling.
  6.  

Throttle shafts and bushings are not included in overhaul kits. They can be purchased separately.

  1. Inspect the idle mixture adjusting needles for burrs or grooves. Any such condition requires replacement of the needle, since you will not be able to obtain a satisfactory idle.
  2.  
  3. Test the accelerator pump check valves. They should pass air one way but not the other. Test for proper seating by blowing and sucking on the valve. Replace the valve check ball and spring as necessary. If the valve is satisfactory wash the valve parts again to remove breath moisture.
  4.  
  5. Check the bowl cover for warped surfaces with a straightedge.
  6.  
  7. Closely inspect the accelerator pump plunger for wear and damage, replacing as necessary.
  8.  
  9. After the carburetor is assembled, check the choke valve for freedom of operation.
  10.  

Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those which deteriorate most rapidly. Failure to replace all parts supplied with the kit (especially gaskets) can result in poor performance later.

Some carburetor manufacturers supply overhaul kits of three basic types: minor repair; major repair; and gasket kits. Basically, they contain the following:

Minor Repair Kits:

All gaskets

Float needle valve

All diagrams

Spring for the pump diaphragm

Major Repair Kits:

All jets and gaskets

All diaphragms

Float needle valve

Pump ball valve

Float

Complete intermediate rod

Intermediate pump lever

Some cover hold-down screws and washers

Gasket Kits:

All gaskets

After cleaning and checking all components, reassemble the carburetor, using new parts and referring to the exploded view. When reassembling, make sure that all screws and jets are tight in their seats, but do not overtighten as the tips will be distorted. Tighten all screws gradually, in rotation. Do not tighten needle valves into their seats; uneven jetting will result. Always use new gaskets. Be sure to adjust the float level when reassembling.

PRELIMINARY CHECKS



The following should be observed before attempting any adjustments after overhaul.

  1. Thoroughly warm the engine. If the engine is cold, be sure that it reaches operating temperature.
  2.  
  3. Check the torque of all carburetor mounting nuts and assembly screws. Also check the intake manifold-to-cylinder head bolts. If air is leaking at any of these points, any attempts at adjustment will inevitably lead to frustration.
  4.  
  5. Check the manifold heat control valve (if used) to be sure that it is free.
  6.  
  7. Check and adjust the choke as necessary.
  8.  
  9. Adjust the idle speed and mixture. If the mixture screws are capped, don't adjust them unless all other causes of rough idle have been eliminated. If any adjustments are performed that might possibly change the idle speed or mixture, adjust the idle and mixture again when you are finished.
  10.  

Before you make any carburetor adjustments make sure that the engine is in tune. Many problems which are thought to be carburetor related can be traced to an engine which is simply out-of-tune. Any trouble in these areas will have symptoms like those of carburetor problems.

 
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