Accelerator pump adjustment, try a higher setting closer to 7/16. Test this on car engine off, make sure throttle does not hang up and this Timing chain? - Slant Six Forum
Chain was good with the one barrel on it and it only hesitates with the choke off / engine cool. I did wonder about metering rods VS accelerator pump. Looking down the carb, the accelerator pump squirts at the first bump of the throttle shaft. I'm willing to give it a go though!