Carb Tuning / Vacuum Problems?

My opinion so far,...

The pistons are either stock or stock replacement, so that + that cam=low cranking psi.
mystery solved.

Second, the idle mixture screws, if I read right.., had no effect on the idle speed or quality....so=your probably idling off the mains.

If you were to raise the initial timing, you'd then be able to lower the idle speed screw down to the 800 rpm range and make the idle mix screws responsive again...btw what can make this worse..is that if you are in the mains...and the pv is rated higher than manifold vac....your drowning the motor in gas.
The added timing will also help low speed responsiveness where the low comp really hurts.

You may find yourself locking out the distributor at 34*....and it still starts...