new carb car won't run

[surfsup]

I bought a new Holley street avenger 670cfm with electric choke, when I installed the carb the motor started right up and runs great, very responsive when I crack the throttle by hand, I took the car out for a drive and it won’t go, I have to rev the hell out of it to get it moving, the car bucks and hesitates something fierce, and a real bad flat spot, when I advance the timing from 12 to 16 the car runs much better but not perfect, I adjusted the mixer with a vacuum gauge to get the highest reading possible, all hoses are correct, I have a new fuel pump about two weeks old, and I’m running with a stock dizzy, the car ran great with the stock 4180 before I replaced it, any ideas on why I have to advance the timing so much to get this thing to run half way decent? I called Holley but could not get through
you can check my profile for mods to the car.

[Gearhead999]

Whoa........just cause it is a "NEW" carb doesn't mean everything is just bolt it on and go.

I'd start by checking the float levels. If they are low it will act the way you're describing. After you get the floats where they belong then you can check the plugs for the proper jets.

The timing shouldn't make any difference, just because you changed the carb.

[surfsup]

did all that, got through to Holley today according to the tec the carb is not compatible with my intake which causes a vacuum leak, there’s a special spacer plate that seals the bottom of the carb. That I need,