tune help

Two reasons:
- when the engine needs more air, it doesn't care where the air comes from...as long as it gets the air.
- the 1405 carb is a 600 cfm unit & has small primary bores. That means air passes through at a higher velocity than say the larger 750 cfm carb, that has larger primaries.
Drilling the pri blades means that the air must pass through the carb & there is a possibility that the high velocity air will pull/dribble fuel from the pri boosters. [ nozzle drip ]. Because the sec bores are larger, velocity is slower, so no nozzle drip.