Chevrolet Full-size Cars 1968-1978 Repair Guide

Carter YF 1-BBL Carburetor

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ADJUSTMENTS



Automatic Choke
  1. Disconnect the choke rod from the choke lever.
  2.  
  3. Hold the choke valve closed and pull the rod up against the stop in the thermostat housing.
  4.  
  5. The top of the rod should be about one rod diameter above the top of the hole in the choke lever. If not, adjust the length of the rod by bending it at the bend.
  6.  
  7. Connect the choke rod at the lever.
  8.  

Hand Choke
  1. Push in the hand choke knob until the knob is within 1 / 8 " of the dash.
  2.  
  3. Loosen the cable clamp at the carburetor and adjust the cable until the choke is wide open.
  4.  
  5. Tighten the cable clamp and check the operation of the choke.
  6.  

Idle Vent
  1. With the choke open, back out the idle speed screw until it is free to close the throttle valve.
  2.  
  3. Insert a feeler gauge between the air horn and the vent valve. Adjust to get 0.065" clearance.
  4.  

Fast Idle and Choke Valve
  1. Hold the choke valve closed.
  2.  
  3. Close the throttle and mark the position of the throttle lever tang on the fast idle cam.
  4.  
  5. The mark on the fast idle cam should align with the upper edge of the tang on the throttle lever. If not, bend the choke rod as necessary.
  6.  

Choke Unloader
  1. Open the throttle to the wide open position.
  2.  
  3. Using a rubber band, hold the choke valve closed.
  4.  
  5. Bend the unloader tang on the throttle lever to get the proper clearance (0.250") between the lower edge of the choke valve and the air horn wall.
  6.  

Vacuum Break
  1. Hold the vacuum break arm against its stop and hold the choke closed with a rubber band.
  2.  
  3. Bend the vacuum break link to establish a clearance of 0.220" (automatic transmission) of 0.240" (manual transmission) between the lower edge of the choke valve and the air horn wall.
  4.  

Float Level
  1. Turn the bowl cover upside down and measure the float level by measuring the distance between the float (free end) and cover. This distance should be 7 / 32 "; if not, bend the lip of the float, not the float arm.
  2.  
  3. Hold the cover in the proper position (not upside down) and measure the float drop from the cover to the float bottom at the end opposite the hinge. This distance should be 1 3 / 16 ".
  4.  
  5. Make any necessary adjustments with the stop tab on the float arm.
  6.  

Accelerator Pump
  1. Seat the throttle valve by backing off the idle speed screw.
  2.  
  3. Hold the throttle valve closed.
  4.  
  5. Fully depress the diaphragm shaft and check the contact between the lower retainer and the lifter link.
  6.  
  7. This retainer (upper pump spring) should just contact the pump lifter link. Do not compress the spring.
  8.  
  9. Bend the pump connector link at its U-bend to make corrections.
  10.  

Metering Rod
  1. Insert the metering rod through the metering jet and close the throttle valve. Press down on the upper pump spring until the pump bottoms.
  2.  
  3. The metering rod arm must rest on the pump lifter link; the rod eye should just slide over the arm pin.
  4.  
  5. To adjust, bend the metering rod arm.
  6.  

 
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