I just got my 3x2 Rochester carbs and need to know what the 3/8 NPT opening is on the base of each carb. Was this for vacuum?? All 3 of my carbs are primary carbs since they will all dump at the same time from on top of my blower. Look forward to the answer. John
They are usually used for the vacuum port for the power brakes and or vaccum operated accessories. Just put pipe plugs in them and that will take care of it.
That is where the PCV valve hooked up on those year engines. A "street elbow" lets you hook it up with trips.