I just rebuilt the two barrell Holley 2100 that's on my '55 Fairlane. I had pulled it off due to a leaking gasket and decided to rebuild it. I put it back on today and fired her up. She sounded great while warming up. I was waiting to ger her nice and warm so I could adjust the idle screw setting and idle mixture screws when she started to lope and run rough. I put some gas to it and it sounded like it was missing. I also heard a hissing/sucking sound. i checked the vacuum line and it was tight at both ends. Any ideas what may be causing the issue? Thanks.

When the engine is running spray carb cleaner around the base to see if you have a bad gasket leak.

Well, it doesn't seem to be sucking anything in at any of the gasket points. When I went out to restart it, the car ran even more rough than before and i had to keep gas on it to keep it running (low and rough idle). I noticed that it seemed to be pulling in a lot of air. I put about 25% choke on it and it instantly ran better, but still rough. So, too much air? Or not enough gas?

Is the carb the 3 bolt type 2 barrel

Yes, three to the intake manifold and three between the bowl assembly and throttle body.

I have the same carb on my car and I rebuilt it. I was having trouble so I called a carb place in florida. They told me that they put the wrong power valve in the kits but the person I called makes his own and he sold me one. He told me they mill off the lip that is around the nut so it is even from the nut to the threads.

Well, you've hit the limit on my carb knowledge. Is the powpower valve the one inside the carb (aka economizer valve)? Would it cause decreased performance as time goes on? If so, where can I get one that'll work?

Yes that is the valve I have to find the carb place number and will let you know. Try your old power valve see if it makes a difference.

here is the name and number

vintage speed 772 778 0809

Great, thanks! I had actually thought about putting the old valve back on. This carb is actually not the one that came with the car, but one that I bought a couple of weeks ago. It had been factory rebuilt by Ford, but way back in '68. I tore it down and replaced all the gaskets as they were falling apart. I also replaced the power and spark valves, but maybe should have left those alone.

I'll play with it some more and see what happens. Thanks again.