GM Full-Size Trucks 1970-1979 Repair Guide

Carburetor

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3



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Fig. Fig. 1: Unfasten the carburetor attaching bolts



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Fig. Fig. 2: Remove the carburetor ...



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Fig. Fig. 3: ... then remove the carburetor gasket

  1. Remove the air cleaner and its gasket.
  2.  
  3. Disconnect the fuel and vacuum lines from the carburetor.
  4.  
  5. Disconnect the choke coil rod or heated air line tube.
  6.  
  7. Disconnect the throttle linkage.
  8.  
  9. If equipped with automatic transmission, disconnect the throttle valve linkage.
  10.  
  11. Detach the CEC valve vacuum hose and electrical connector.
  12.  
  13. Remove the idle stop electrical wiring from the idle stop solenoid, if so equipped.
  14.  
  15. Unfasten the carburetor attaching nuts and/or bolts, then remove the carburetor. Remove the gasket or insulator, as applicable.
  16.  
  17. Install the carburetor using a reverse of the removal procedure. Use a new gasket and fill the float bowl with gasoline to ease starting the engine.
  18.  

IDENTIFICATION



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



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 all 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 disassemble, 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 a clean, lint-free cloth.

Blow out all passages and jets with compressed air and be sure that there are 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, replace 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 it; 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 as necessary. If the valve is satisfactory, wash the valve again to remove breath moisture.
  4.  
  5. Check the bowl cover for warped surfaces with a straightedge.
  6.  
  7. Closely inspect the valves and seats 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 supplies 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.

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.

 
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