273 2V bogging

After warming up the 273 in a ‘67 Barracuda it wants to bog down real bad with a quick opening of the throttle. Tried moving the timing but no real difference. Tried moving the accelerator pump with no real difference. What does seem to make a difference is to partially close the choke valve. When blipping the throttle there looks like a ton of fuel going in and that little engine sucks a lot of air. This engine sat for many years without starting. Carb is rebuilt. We can’t tell if it is getting too much air, or fuel or both.

too much air !

check idle circuts , float level , give it the max pump shot .

set timing to fact spec.

vac leak. spray starting fluid around & see what develops (block the carb with a sheet of thin cardboard etc when spraying to avoid a false positive from fluid getting sucked into the carb throat top). I'd get the RPM up to "medium" or even higher & jerk the throttle & see if it still kicks out a good shot.

Have you checked the vacuum advance?

If the hesitation is worse when the engine is cold the exhaust passageway thru the intake that is there to heat the manifold for better fuel atomization could be blocked with carbon buildup. Had a 69 Barracuda with a 318 that drove me crazy. Finally pulled the intake and the passage was blocked solid. Chipped it clean and solved the bog issue.

The OP states "After warming up " probably not a blocked crossover or the choke wouldn't open.

Here’s the plan. I’m confident with the mixture screws. Go back to factory timing which is 5* before. Lower float level because I did notice gasket on the top staying wet. Verify the vacuum advance. Check for vacuum leaks. Then see where it from that point.
The intake crossover was stopped up solid which looked like someone had poured block filler in it.
Still have the valves to adjust but on its initial run down the street that little engine has a respectable amount of torque.

On my first car, a 1969 Plymouth Fury with a 318, the engine would just about die with a stab of the throttle. I rebuilt the carb and noticed the check ball in the bottom of the accelerator pump well was missing. Put a ball from the kit in there, new pump piston and all was well.

I try 15 or even 20 initial (wont hurt you for a test) if it ain't pinging then no harm no foul.

I rebuilt the carb and I was careful to make sure the ball got back in there. But I am going to confirm when I reset the float level.
Rapid we have run the timing up as far as 15 but not 20.

If 15 didn't do it then yes the prob is elsewhere.