Distributor Vacuum Advance?

If you really want to know how manifold and ported vacuum work try what I did. Get 2 vacuum gauges a couple of vacuum t's and some extra vacuum hoses. connect one guage to manifold vacuum and one to ported vacuum. You can route the gauges through the door if it doesn't pinch the hoses shut. Put the gauges side by side where you can see them both while driving. It works best visually if they are matching gauges but not a requirement. By the way they can be had fairly inexpensively and don't need to be top of the line for this test. A little duct tape and cardboard is what I use to hold them in place. I have also duct taped them to the outside windshield. What I have found is that as soon as the throttle plates are cracked open the 2 gauges read the same. They read the same at wot which is nearly zero. That has been my experience. I encourage others to gather their own data and find out for themselves instead of taking mine or anyone else's word for it.