Please do not over jet...63/4's is a not recommended.
62's may even be too large if this is nothing high hp, 61 may likely be required.
The secondaries when closed are constantly providing fuel...always...so they make up the rest of the jetting total - they have adjustment screws to add or subtract fuel
When the secondaries open they provide air/more fuel and of course the OH WOW! acceleration. Let me see that happen with efi or a 4bbl....I'm waiting

More than likely the six pak set up and the over all tune up is not Goldilocks [just right] so there are problems like surging etc etc etc