The biggest problem with any adapter is another mating surface. So another chance for vacuum leak or baseplate deformation.Well you can watch down the bore and see its getting gas really good. Its always a steady squirt. Also this the the first time I had use a 2-4 carb adapter. Have you had any dealings with them?
If it is sucking a bunch of air someplace other than the throat of the carb that can cause you starting issue.
Today's parts are much better than what we had it the 80's so don't see it near as often. But then now we have the influx of chinese parts and you just never know what you get.
I have a vacuum leak. Not on the carb, not on the adapter. I have gone so far as to remove every vac line. So I am left to believe it is the intake to head mating surface somewhere. How do you find that? LOL I hate this car. It is a brand name intake but made in china and it did seem to fit "funny" when I installed it.
Never the less it does run well. Even with the leak. So maybe I will sell rather than fix.