My thoughts;
Assuming that
1) your distributor is functioning correctly, ie that the mechanical advance weights are snapping back nicely and that the VA is functioning correctly, and
2) your hot lash is adequate, and
3) your engine is up to temp,
4) Make sure the CC is ventilated.
5) Make sure the float bowls are ventilated.
6) assuming the carbs are internally functioning correctly, and that the WET fuel-levels are at least the same.
7) If your carbs
are off cars before the PCV system was invented, and they do not have PCV nipples then the throttles may have to be opened further than usual to provide adequate Idle-Air, and so, the intake may be getting too much air. IDK what I would do, probably I would drill holes in the Throttle valves, so I could synchronize the Transfers and the mixture screws. But honestly, I would sure like to install a PCV System, even if just a continuous idle bleed..
If both carbs have PCV nipples, I would splice them together and install a restrictor up near the PCV. This system has to discharge just underneath the Throttle valves, somewhere close to the fuel discharge ports. If you try to send it to just one or perhaps two intake runners, then you will have tuning issues.
8) Or perhaps your throttles are just TOO FAR open, and the transfers won't quit flowing.
Close the throttles until the transfers are just a hair shorter than wide, under the throttles. Reset the mixture screws as may be required, somewhere around 2 turns out.
If the idle speed is too slow, increase the ignition timing.
If the idle speed is too fast, retard the ignition timing.
Check for a Tip-in sag.
This is often and usually caused by the transfer slots being a hair too far closed, or a low fuel level. Fix it
After you get that dialed in, here are some other tips;
9) you may have to reset your accelerator pump linkage, and
10) you may have to revisit your Power-Timing.
11) If your rpm flares up a lil when you lift off the gas, then the carb was running rich just before you lifted.
12) if, in First gear, the nose drops noticeably when you lift, she was running lean at the lift.
13) if the Rpm drops more than 100 rpm when going from N/P to in-gear, then the engine has too much Idle-power. For correction, your choices are; Less Idle-Timing, Less Idle-Air, or less Idle-speed, in that order, usually..
14) if all else fails, look for a restricted exhaust.
Just so you know,
I like to set my valves at ambient temp (65/75*) and Mine are set to 013intake/023exhaust. This should produce a more consistent idle.
You can play with that later.
If you play with lash during this orientation, you get to start over.
These are my opinions.
Others
may have different opinions.
