vacuum advance/boost retard

[Tom Cloud]

a coupl'a months ago, I asked about setting up distributors and got
lots of good advice.  Now, I want to expand that into the vacuum
advance arena.

Here's the specific question: ....  can vac advance work correctly
with a mild to wild cam?

I'm looking into getting the Accel timing computer.  It allows
setting timing at 500 rpm increments (rather than a flat line
between idle and some max point like MSD, etc) and it has an input
for a MAP sensor to give advance/retard with vac/boost.  (My engine
isn't blown, so I don't need the retard feature.)  This function
works similar to that on a regular distributor in that a certain
pressure produces a specific amount of offset in degrees -- regardless
of the rpm.

On my E-303 on my 351W, I get about 10-12" Hg at idle, about 15 to 18 at
cruise and the expected 20+ at decel. The vac drops to dead zero at any
acceleration.  I can't see how 'ported' vacuum would work at all with
this crappy vacuum -- seems that you want the first off-idle opening
to advance the distributor and I can't see how I'd get any.  And I'm
not clear how the manifold vacuum would function as an input either.
I guess that you'd just set the system up to work without detonation
with no vacuum input and then increase the vac advance in small
increments until detonation occurs at slight acceleration and then
back it off ?????

Any suggestions ?    Warnings ?

thanks,
Tom Cloud

     Madness takes its toll   .....   please have exact change