If it were mine , I would replace both needle valves and also check the floats to make sure that don`t have a leak/pinhole in them . The fuel today deteriorates fairly quickly and forms varnish if left sitting for any period of time . I had the front carb on my 427 Galaxie do just that last week . Took the float needle valve out and let it soak in lacquer thinner for several hours , checked it for free action and reinstalled ( they were new as of this spring ). Engine ran fine . Same symptoms you had ... the car started fine , started running rough , cleared up some and then wouldn`t start and plugs showed wet .
I don`t drive the Galaxie that much anymore and the fuel sits in the carb and causes problems over time .
Jegs and Summitt both have aftermarket float needle valves from folks like Barry Grant etc that are good quality ... try not to use something from one of the discount autoparts houses as their quality can be suspect .
I couldn`t tell from your postings if the carbs were Holly or not , but if you had a backfire , you might want to replace the power valves ... if leaking , they can give you a fit . Adjust the float levels with the engine running or you will get a false reading .

Good luck.

Car now starts fine and idles, but now lags when accelerator is initially pushed, and then catches up. Also has some backfire on deceleration, which it never had before. Float level are right at the bottom of the sights, where it laps out due to engine vibration, but is not a constant stream.

Its getting closer, but still needs some fine tuning. Any suggestions on what is causing and how to eliminate these latest issues?

Finally gave up and took the car to a real carb expert. He found multiple problems caused by the initial "expert" that tweaked my carbs, including at least one blown power valve, damaged needle/seats, and incorrect float adjustments. Both carbs were taken off, and new parts installed and adjusted. Car now starts right up, and runs fine. I only lost about four weeks of driving time :CRY: - Never again.

Lesson learned: Never let another touch your car, unless you are absolutely sure he is qualified.

Thanks to all who submitted suggestions. It seems that there were just too many issues to overcome, requiring the carbs to be stripped back down to start at zero again to ensure all was correct.

Great to hear that it's back on the road again!

Ray

I stand by my previous post.:p

I've had a friend in 69 that his original 390 wouldn't resart when leaving a grocery store. I pulled the plug wire and it had spark so I went on to other sources. Someone else figured it out . It had a points distributer. The condenser was giving up. It would work just long enough for me to see it spark once or twice then quit. I bought a coil condenser tester and have used it ,maybe , twise since. Also had my Cobra replica quit at a traffic light, turned out to be a bad conection between the glass fuse and contactson the glass fuse holder. Seems something is allways causing problems, but you can usually fix them.
Also any back fire or the like can damage the powervalve problem. and if you are using a original points distributor and coil , they use a lower voltage (resister) for running, and straight 12V for starting. Ford used a starting solenoid that has two small terminals one terminal was from the trigger or switch, the other terminal was the resister bypass for starting. Coil ran off resisted power when running and received full 12V when starting. Some cars had a ceramic ballast resister inline, and some years used a longer length of wire folded back and forth in the wire harness to get the desired resistance ( I parted out a 61), and some used a special wire with a higher resistance to supply the coil (pink as I remember).
If the wire that normally supplied power to the coil were seperated from power from the ignition switch source ( blown fuse ,broken or disconnected wire terminal, bad wire,etc. and yes the ceramic balast resisters can burn out and break), the engine would try to fire when cranking but but would stop when the switch was released. Do you have an original points distributor and coil, and what type of resistor are you using?