Holley 6709 double pumper 750 carb info

I am pretty sure that blow out protection came MANY years the 4 bbl intro in 1957. I would think a first year engineering student would have picked up on that failing. Likewise the acc pump transfer port that had a tendency to leak. Eventually a brass tube with an o ring each end was fitted to solve 'the problem'.
Carters were perfectly designed from day one, didn't need upgrades...