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    GM Cadillac 1967-1989 Repair Guide

    Rochester M4ME, E4ME, E4MC 4-BBL Carburetors

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    See Figures 1 through 18FLOAT LEVEL ADJUSTMENT

    1. Remove the air horn.
    2.  
    3. Hold the float retainer in place and lightly push down on the float against the needle.
    4.  
    5. Measure the gap between the casting surface and the top of the float at a point 3 / 16 in. back from the float toe.
    6.  
    7. To adjust, remove the float and bend the float arm.
    8.  
    9. On CCC carburetors, if the float level varies more than 1 / 16 in. either way, adjust as follows:
      1. Level too high: Hold the float retainer firmly in place and push down on the center of the float body until the correct gap is attained.
      2.  
      3. Level too low: Lift out the metering rods. Remove the solenoid connector screw. Turn the lean mixture solenoid screw clockwise counting the number of turns until the screw is lightly seated. Then, remove the screw. Lift the solenoid and connector from the float bowl. Remove the float and bend the arm to adjust. Install the float and check the adjustment. Install the mixture screw to the exact number of turns noted earlier. Install all other parts.

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        Fig. Fig. 1: Common quadrajet float level adjustment



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        Fig. Fig. 2: Common 4-barrel front vacuum break adjustment



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        Fig. Fig. 3: Secondary opening adjustment - M4ME, E4ME



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        Fig. Fig. 4: 4-barrel rear vacuum break adjustment (without adjusting screw) - through 1980

      4.  

    10.  

    1975-80
    1. Place the cam follower lever on the highest step of the fast idle cam.
    2.  
    3. Remove the choke cover and coil assembly from the choke housing.
    4.  
    5. Seat the front vacuum diaphragm using an outside vacuum source.
    6.  
    7. Push up on the inside choke coil lever until the tang on the vacuum break lever contacts the tang on the vacuum break plunger.
    8.  
    9. Place the proper size gauge between the upper edge of the choke plate and the inside of the air horn wall.
    10.  
    11. To adjust, turn the adjustment screw on the vacuum break plunger lever.
    12.  
    13. To adjust the secondary vacuum break, with the choke cover and coil removed, the cam follower on the highest step of the fast idle cam, tape over the bleed hole in the rear vacuum break diaphragm.
    14.  
    15. Seat the rear diaphragm using an outside vacuum source.
    16.  
    17. Close the choke by pushing up on the choke coil lever inside the choke housing. Make sure the choke rod is in the bottom of the slot in the choke lever.
    18.  
    19. Measure between the upper edge of the choke plate and the air horn wall with a wire type gauge.
    20.  
    21. To adjust, bend the vacuum break rod at the first bend near the diaphragm.
    22.  

    1981 and Later

    The carburetors require special tools for adjustment. Service is best left to a professional mechanic.



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    Fig. Fig. 5: Adjusting the air valve rod - M4ME, E4ME



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    Fig. Fig. 6: Secondary lockout adjustment - M4ME, E4ME



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    Fig. Fig. 7: Secondary closing adjustment - M4ME, E4ME



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    Fig. Fig. 8: Adjusting the air valve spring - M4ME, E4ME

    FAST IDLE CAM ADJUSTMENT



    1. Adjust the fast idle and place the cam follower on the second step of the fast idle cam.
    2.  
    3. Close the choke plate by pushing counterclockwise on the external choke lever. On 1975-80 models, remove the coil assembly from the choke housing and push on the choke coil lever.
    4.  
    5. Measure between the upper edge of the choke plate and the air horn wall.
    6.  
    7. To adjust, 1975-80 models, bend the tang on the fast idle cam. Be sure that the tang rests against the cam after bending.
    8.  

    CHOKE COIL LEVER ADJUSTMENT



    1. Remove the choke cover and thermostatic coil from the choke housing.
    2.  
    3. Push the coil tang counterclockwise until the choke plate is fully closed.
    4.  
    5. Insert a 0.120 in. gauge into the hole in the choke housing. The lower edge of the choke coil lever should just contact the side of the gauge.
    6.  
    7. Bend the choke rod to adjust, if necessary.
    8.  



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    Fig. Fig. 9: Float adjustment - E4MC



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    Fig. Fig. 10: Air valve return spring adjustment - E4MC



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    Fig. Fig. 11: Choke stat lever adjustment - E4MC



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    Fig. Fig. 12: Choke link/fast idle cam adjustment - E4MC

    AUTOMATIC CHOKE ADJUSTMENT



    1. Loosen the choke housing cover screws.
    2.  
    3. Place the fast idle cam follower on the highest step of the fast idle cam.
    4.  
    5. Rotate the cover and coil assembly counterclockwise until the choke plate just closes.
    6.  
    7. Align the index mark on the cover with the specified index point on the housing.
    8.  
    9. Tighten the retaining screws.
    10.  

    UNLOADER ADJUSTMENT



    Through 1980
    1. With the choke plate completely closed, hold the throttle plates wide open.
    2.  
    3. Measure the distance between the upper edge of the choke plate and the airhorn wall.
    4.  
    5. Bend the tang on the fast idle lever to adjust.
    6.  

    1981 and Later

    The unloader adjustment on these carburetors requires special tools and is quite complicated. Service here is best left to a professional mechanic.



    Click image to see an enlarged view

    Fig. Fig. 13: Choke valve angle gauge - E4MC



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    Fig. Fig. 14: Primary side vacuum break adjustment - E4MC

    VACUUM BREAK ADJUSTMENT AIR VALVE ROD ADJUSTMENT



    1. Using an outside vacuum source, seat the choke vacuum diaphragm. Put a piece of tape over the purge bleed hole if so equipped.
    2.  
    3. Close the air valve completely.
    4.  
    5. Insert the gauge between the rod and the end of the slot in the lever.
    6.  
    7. Bend the rod to adjust the clearance.
    8.  

    SECONDARY LOCKOUT ADJUSTMENT



    1. Pull the choke wide open by pushing out on the choke lever.
    2.  
    3. Open the throttle until the end of the secondary actuating lever is opposite the toe of the lockout lever.
    4.  
    5. Measure the clearance between the lockout lever and the secondary lever.
    6.  
    7. Bend the lockout pin until the clearance is in accordance with the proper specifications.
    8.  

    SECONDARY CLOSING ADJUSTMENT



    1. Make sure that the idle speed is set to the proper specifications.
    2.  
    3. The choke valve should be wide open with the cam follower off of the steps of the fast idle cam.
    4.  
    5. There should be 0.020 in. clearance between the secondary throttle actuating rod and the front of the slot on the secondary throttle lever with the closing tang on the throttle lever resting against the actuating lever.
    6.  
    7. To adjust, bend the secondary closing tang on the primary throttle actuating rod.
    8.  



    Click image to see an enlarged view

    Fig. Fig. 15: Secondary side vacuum break adjustment - E4MC



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    Fig. Fig. 16: Unloader adjustment - E4MC



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    Fig. Fig. 17: Air valve link adjustment (primary side) - E4MC



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    Fig. Fig. 18: Secondary throttle lockout adjustment - E4MC

    SECONDARY OPENING ADJUSTMENT



    1. Open the primary throttle valves until the actuating link contacts the upper tang on the secondary lever.
    2.  
    3. With the two point linkage, the bottom of the link should be in the center of the secondary lever slot.
    4.  
    5. With the three point linkage, there should be 0.070 in. clearance between the link and the middle tang.
    6.  
    7. To adjust, bend the upper tang on the secondary lever.
    8.  

    AIR VALVE SPRING ADJUSTMENT



    To adjust the air valve spring windup, loosen the Allen head lockscrew and then turn the adjusting screw counterclockwise so as to remove all spring tension. With the air valve closed turn the adjusting screw clockwise the specified number of turns after the torsion spring contacts the pin on the shaft. Hold the adjusting screw in this position and tighten the lockscrew.

     
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