I have that cam in a 440 with a single plane intake and at 700 rpm idle it holds 14 inches of Hg. Your numbers seem low, meaning more initial timing is in order. The timing is jacked up too. The vacuum advance is limited to only 9 or 10 degrees advance, from manifold vacuum (not ported). My base timing is 20 initial and 33 total all in by 2100. This means that at idle, it has 30 degrees of advance. Also check out automotiveu.com.