Checked a holley manual and while they show it in pictures, I dont see anything to identify what the screw on the bottom corner of the front passenger side of the carb is? Is this some type of idle adjustment?
I believe that is a vacuum port.. seems like it's not in use, so it has been 'blanked' off, by using a short piece of rubber hose/tubing, and running a screw into it as a blank. You could just tug on it and it would come straight off to confirm.. Should be a small brass tube, normally used as a vacuum source for distributor.
Thanks so much - cant believe I was afraid to turn the screw lol. I will get a proper vacuum cap for it. With the info you gave was able to locate in the manual - it is a manifold vacuum used for intake (I dont have this option on my air cleaner- should I?), ac/cruise etc.
Also says to hook power brakes and pvc valve to same port on the carb but I have my power brakes directly to the top of the manifold - should k change this?