Chevrolet Full-size Cars 1968-1978 Repair Guide

Rochester BV 1-Bbl. Carburetor

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ADJUSTMENTS



Automatic Choke
  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


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Fig. Fig. 1 Idle vent adjustment for the Rochester BV carburetor

  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".
  4.  
  5. If an adjustment is necessary, turn the valve, using the proper tool.
  6.  

Fast Idle and Choke Valve
  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" 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
  1. Open the throttle to the wide open position.
  2.  
  3. A 0.230-0.270" gauge should slide freely between the lower edge of the choke valve and the bore of the carburetor.
  4.  
  5. If necessary, bend the throttle tang to obtain the proper clearance.
  6.  

Vacuum Break
  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" on Powerglide transmission equipped vehicles and 0.154-0.173" on manual transmission equipped vehicles.
  4.  
  5. Bend the diaphragm link, if necessary.
  6.  

Float Level


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Fig. Fig. 2 Adjusting the float drop on the Rochester BV carburetor

  1. Remove the air cleaner.
  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.
  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 float 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 ", bend the stop tang until the drop is correct.
  4.  
  5. Install the cover and reconnect the lines and linkage in the reverse order of removal.
  6.  

 
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