[Jerry Clayton]

The inlet valves are NOT OPENED by fuel pressure!!!Gravity causes the float to drop, opening the needle seat. With larger diameter needle/seat assys, too much pressure will force them to leak overrunning the carb at the vents.
Also--too much volume/pressure can cause a carb to syphon fuel thru the vent at higher engine rpm.

I like to set carbs up with around 3 1/2 to 4 1/2 pressure and reasonable needle valve assy for the type of driving the car sees.