I have a stock 351 w with 4brl carburetor is stock I think. Its a 4300 series with a tag that says C9ZF D. I have had trouble with it idling. This is what I have done with the fuel issues starting with the replacement of the gas tank and the sending unit replaced fuel filter at carburetor. I removed the carburetor and bought a rebuild kit from my friends at WCCC. I noted a lot of black gunk build up in the manifold but the carburetor was varnished but not real bad, it cleaned up well. To date I tried to start it and fuel was pushing out the two top port that look like vent hole in corroborator.Took it apart twice with same issue. I was able to stop that issue after I removed the AUX needle seat and gasket and replaced it with the existing one that did not have the needle and seat it appeared to be leaded in. Is that normal somehow? I was able to get it started and it responds to throttle but i cannot seam to control the idol speed from the spring Idle mixture screws. I move them and nothing changes. I am not a carburetor guy but I fill its something I should be able to do myself so I have. I Need some help.If there is something I need to buy the check some setting. I believe I can learn.
BTW its in A 1969 cougar eliminator with a automatic.
The carburator idle circuit only comes into play with the throttle plates closed. Usually a “no” or rough idle is caused by vacuum leaks. One trick we used back in the day was to use needlenose pliers to gently pinch off vacuum hoses to eliminate possible leaks.
I am assuming that you have fixed the flooding conditions that you described.
Yes when I reinstalled the old (Aux) needle and gasket assembly without the needle.
I should say that the old one did not have that needle assembly in it.
The 4300 series carburetor came up in another thread recently with a few defenders and myself among the detractors. Mine was prone to leaks, couldn’t be properly tuned to start cold, and after a rebuild and having it behave exactly like it did before tear down, I junked it and bought a Holley vacuum secondary 4V carb and never looked back.
As noted above, but absolutely worst of the symptoms was a nagging leak from the airhorn around the fuel filter inlet elbow. I found a puddle of gas in between the intake runners more than once which was the final straw. No engine fires, please.
I have had success (after 2 attempts) at rebuilding my 4300. Blocking off the auxiliary valve eliminates the overflowing “toilet” issue on the 4300s. Also making sure that the floats are centered is another area of concern. The following link discusses how I rebuilt my 4300, although mine is for 67 Cougar (the 67 4300s have an air idle bypass screw that was unique to 67 only).
Good luck
Coach Jack