64 427 way too rich

[Automan]

Hi: So i have a 1964 427 2x4 1850 600cfm carbs. iron heads. She is running way too rich. These carbs are new. I bought them off of EBAY from a seller that has really good history. He's the sellor that powder coats his carbs. I got the powder blue ones. Looks really nice.

Anyway, this is whats happening. When i begin my drive cold. Everything runs really nice except for the puff puff sound that i get when running at a consistant rpm coming out of my passenger side pipe. As the drive gets longer i begin to have hesitation on acceleration, i have to keep it at 1100-1500rpm at stoplights to keep it from bogging down. Also it starts to backfire slightly.

Now, these being new carbs 1850-list, 600cfm, the sell said that they are pre tested on engines and ready to go. Now my guy went ahead and adjusted the flow levels to the point where the can was just hitting the set screw opening where you can see the level. I hope that makes sense to you all. Can too high of bowl level make the carbs run too rich.

Now both carbs have vacuum diapgrams for the secondaries but they are not linked together because there is no outlet to do so. So they must open up individually.

I have a 15 gallon tank that seems to be giving me 50 miles to the gallon only. I had 750cfm and they told me that they are way to rich of carbs for my engine. So now with these they are giving me the same statement.

Please help me. Dont know who to believe anymore.
Extremely frustrated.
Automan