1955 with 312 & Autolite 4100 secondaries leaking fuel | Ford Thunderbird club group 1955-2005 T-Bird models

1955 with 312 & Autolite 4100 secondaries leaking fuel

  • Thread starter Thread starter Critterpainer
  • Start date Start date
Critterpainer

Critterpainer

Reaction score
110
Thunderbird Year
1955
My Bird has always run rich but smoothly for the 5 years I have owned it. Last year I removed and rebuilt the carburetor. I cleaned passages and jets, replaced the wear parts and re-assembled it. When I was done there was no change except it possibly running a tad richer at idle. Tossed in the towel and took it to a carb specialty shop that came highly recommended. Got it back, installed it and it ran better than ever EXCEPT at idle. I could not get the idle below 675 or so and I could not get a smooth idle. Frustrated I parked the car through the AZ summer. Found time to tinker today after driving it and sealed all potential vacuum leaks with no change in idle speed. I noticed the secondary venturis were wet and fuel was entering the secondaries. I shoved a rag into the secondaries and the idle smoothed and the RPM dropped. The butterflies appear to be closed and I backed off on the adjustment but it still is drawing fuel in through the secondaries. The secondary throttle shaft bushing was changed as part of the rebuild.
what am I missing?

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I had the same issue with the carb on our 56 Bird when it came back from a California rebuilder. I could see light around the secondaries when they were closed ☹️

When I returned the carb to them, they 'couldn't find a problem'. But following return and then reinstalled, the high idle problem was miraculously solved ... and the secondaries now closed tightly!
 
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