To clarify: one reason why I think the response should really be better is not only that the distance is really short (like a Hilborn stack), but that the "buffer" (plenum) volume, which damps the vacuum pulse, is tiny.
When the intake valve cracks open, this pressure differential is always diluted by the empty space between the valve and the venturi. At WOT the vacuum is only 1.5-3.0" Hg, so any reduction at all slows fuel discharge from the main nozzle.
The 5-7 pairing also enriches mixture from the carburetor - a staggered sequence has proven to be stronger at the nozzle than more equal intervals. The carburetor intervals with conventional SBC V8 1 8 4 3 6 5 7 2 firing order:
1-3 (left front pair) 270° - 450° - 270°
2-4 (right front pair) 270° - 540° - 270°
5-7 (left rear pair) 90° - 630° - 90°
6-8 (right rear pair) 450° - 270° - 450°
{breathe}
