GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Rochester BV 1-BBL Carburetor

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AUTOMATIC CHOKE ADJUSTMENT



  1. Disconnect the choke rod from the choke lever at the carburetor.
  2.  
  3. While holding the choke valve shut, pull the choke rod up against the stop in the thermostat housing.
  4.  
  5. Adjust the length of the choke rod so that the bottom edge of the choke rod is even with the top edge of the hole in the choke lever.
  6.  
  7. Check the linkage for freedom of operation.
  8.  

IDLE VENT ADJUSTMENT



See Figure 1

  1. Position the carburetor lever on the low step of the fast idle cam.
  2.  
  3. The distance between the choke valve and the body casting should be 0.050 in. (1.27mm).
  4.  
  5. If an adjustment is necessary, turn the valve using a screwdriver.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Idle vent adjustment-Rochester BV

FAST IDLE AND CHOKE VALVE ADJUSTMENT



  1. Position the end of the idle adjusting screw on the next to highest step of the fast idle cam.
  2.  
  3. A 0.050 in. (1.27mm) feeler gauge should slide easily between the lower edge of the choke valve and the carburetor bore.
  4.  
  5. If necessary, bend the choke rod until the correct clearance is obtained.
  6.  

UNLOADER ADJUSTMENT



  1. Open the throttle to the wide open position.
  2.  
  3. A 0.230/0.270 in. (5.842/6.858mm) gauge should slide freely between the lower edge of the choke valve and the bore of the carburetor.
  4.  
  5. If necessary, carefully bend the throttle tang to obtain the proper clearance.
  6.  

VACUUM BREAK ADJUSTMENT



  1. Hold the diaphragm lever against the diaphragm body.
  2.  
  3. The clearance between the lower edge of the choke valve and the air horn wall should be 0.136-0.154 in. (3.454-3.912mm) on Powerglide cars and 0.154-0.173 in. (3.912-4.394mm) on manual cars.
  4.  
  5. Bend the diaphragm link, if adjustment is necessary.
  6.  

FLOAT LEVEL ADJUSTMENT



See Figure 2

  1. Remove the air cleaner assembly.
  2.  
  3. Disconnect the fuel line, fast idle rod, cam-to-choke kick lever, vacuum hose at the diaphragm, and the choke rod at the choke lever.
  4.  
  5. Remove the bowl cover screws and careful lift the cover off the carburetor. Use extra caution not to drop and loose the screws in the engine.
  6.  
  7. Install a new gasket on the cover before making any adjustments.
  8.  
  9. Invert the cover assembly and measure the float level with a float gauge.
  10.  

Rebuilding kits include a float level gauge.

  1. Check float centering while holding the cover sideways. Use the same gauge as in Step Five. The floats should not touch the gauge.
  2.  
  3. Hold the cover upright and measure the float drop. If the drop is more or less than 1 3 / 4 in., bend the stop tang until the drop is correct.
  4.  
  5. Install the cover and carefully tighten the retaining screws, then reconnect the lines and linkage
  6.  



Click image to see an enlarged view

Fig. Fig. 2: Adjusting the float drop-Rochester BV

 
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