Expert: Vern Bullock - 5/21/2008

Question
Hi I have a 1954 Pontiac straight 8 that I recently had the carburetor rebuilt. I did the whole setting of the butterfly valve as instructed by the mechanic. I can get the car to start but it will only run if you keep the gas pedal pressed. (car ran perfectly before the rebuild except the carb leaked)if i take my foot off the accelerator the car will not idle and dies. Also seems to be flooding. Now I don't know much about carburetors and I seem to recall from auto shop 20 years ago that the 2 screws in front are for fuel air adjustment. Also is it possible the vacuum line is leaking? Perhaps I did not get it all the way tightened down. Would that keep it from idling? Can you help me out?   Thanks

Answer
Hi Ed:
Identifying the correct problem might be a little tricky.

First check to make sure your butterfly valve isn't stuck. Also check to make sure your automatic choke isn't stuck as well. If these things checks out, then check your vacuum.

Usually if you have a vacuum leak, it will run rough, but not cut off. Unless the leak is really bad. So, check the vacuum also. However, it could be the idle needs adjusting. If so, turn the idle screw a 1/2 turn. That's the large screw on the carb with the spring in it. It should rest against the accelerator linkage. This may be all that is needed. Finally, check your air/fuel mixture.

The air/fuel adjustment screws should only be adjusted if you are running too rich or too lean. If it seem to be flooding, you could be running too rich. So, you may want to decrease fuel flow and increase air flow just a bit to see if it runs a little better. Don't over adjust. Only turn these screws 1/4 turn at a time.