If your carb is brand new its unlikely to be that, aside from possibly volume/idle screw setting but that only really affects idle circuit not on acceleration.
Before you dive in, check valve lash is correct.
First thing is to check the carb is fitted with correct gaskets etc.. in good condition. Fit it dry, no sealant.
Check static timing (try 6deg BTDC) and with a strobe after if you have one. Check the engine advances smoothly on the strobe when you rev it.
Check your vac advance tube and mechanism by sucking on tube (carb end) then making sure advance mech under dizzy cap moves freely. Little oil on there may help. Its hard to get enough suck to move it much unless your Jenna Jameson :lvhello-065:
Another one to check is run the engine up to warm and let it idle with no choke; spray easy start/carb cleaner all around seating of carb then inlet manifold. Be careful, its flammable, have a CO2 extinguisher on standby! Watch the exhaust as its close and will be hot. If the engine note changes with a spray of Easy Start/cleaner then there's an air leak near where you sprayed. Most probable area is Inlet manifold gasket or carb seating. As someone said try the throttle spindle for good measure.
Exhaust leak maybe would cause this? Worth a little check in case at the manifold to downpipe connection.
Get the engine up to temp and with no choke try revving engine slowly and then quickly to see if it reacts differently. If it revs smoothly when throttle is opened gradually, then it could be accelerator pump causing issues. Unlikely with a new carb as I said but it could have sucked some crud into the jet I guess or it may be faulty from new? Take the inlet off and pump the throttle arm to make sure it gives a nice fat jet of petrol, not a dribble or thin pi$$
It could be your fuel pump also or a blocked inline filter. Again, less likely perhaps if its running ok on choke.
Enough things for you to check
? I have exactly the same issue by the way and am working through things slowly. With a 5 month old baby :baby:and work its not easy to find 20 mins on a weekend to sort! I've tried old carbs, new carbs, webers, zeniths........ :5bbanghead: It did run smooth at one point but I've changed so much stuff for various reasons I've forgotten what worked! By the way, Zeniths AND Weber 34ich are a bit sh*t in my opinion and as someone above said. Before you go spending £150 on fitting an SU or 32/34 Weber or something just check out all other possible causes. It may not even be fuel related? Who knows with these old landies!
Just don't leave anything to chance if its free to check it.
My money is on the advance in the dizzy for mine...............:mil5:
