performance tune up instructions:
http://www.gnetworks.com/v4files/bar...withimages.pdf
at idle rpms a carb needs about 12Hg absolute minimum to make a half way decent "atomized" mix...
at 8-10 Hg idle and rumpity rumpity (bad idle mix on purpose) you are dripping liquid gas into the cylinders and that is not a good thing (washing the oil off the walls and contaminating the oil and fouling the plugs)....
stock or mild cam with a dual plane manifold is (ideal) 18Hg at 700rpms with 10-12 base...
sounds like you have a signifigant vacuum leak if 14-16 base only shows 10Hg (or your vac gauge is reading way way off calibration)....
just fyi:
a typical (268 duration) street performance cam with a dual plane will show 15Hg at 700-800 with 14-16 base,,,,10Hg on that cam means there is a "inhale" problem...
a open plenum manifold will cause low Hg,,,if you have one get rid of it....
edit: there are more good articles on that Barry Grant Demon carb site...