No, they usually work decent as shipped. It sounds like you have a timing/spark issue since the carb is new. If the coil is weak, plugs old, and wires old, vacuum canister not working, you need to troubleshoot further. I would start with simple tune-up first. Fresh plugs, plug wires, points, condenser, timing set to at least 12*btdc, check fuel pressure, check vacuum canister for proper advancing of timing, coil, fuel filter, ground wires, battery cables, engine grounded, etc. Then let us know more. Joe-JDC