[sidewaysinthird]

Like Ernie, I made use of "manifold" vacuum to allow for fairly wild cam profiles. Its when Texas started doing emissions testing that I found it be of use getting the Nox numbers down far enough to pass inspection with a healthy 377 de-stroked 400 Chevy. I also had some sucess with keeping temps down in the Houston traffic using manifold sourced vacuum instead of ported. However ported vacuum is what stock engines ran all through the 60's and 70's, and it works very well for most when the max centrifigal advance is limited as the typical stock distributor tend to be.

Accel used to make an adjustable vacuum advance for many applications, which when set up properly can vastly improve idle quality on most mild cam engines be it used in ported or manifold vacuum situations.

Good luck to you getting the tune just perfect.

Mike