On my 475ci tomahawk BBB I run a MOPAR Super Victor manifold, Bobb Makley welded the plates to it, my buddy Jay did some serious port work, has been great... BUT recently when I started the car I noticed that I was not pulling vacuum, I had raced the car about 1 week prior, ran good, 5.65 @123 on one unit, no “issues”., Motor always pulls vacuum off idle, and it showed ZERO.. I end up pulling the pump apart, flipped the vacuum pump vanes, ran motor with a remote vacuum gage, still zero, disconnected pump line from the valve cover, and it sucked to my hand., Did a compression check, all good.. I started looking at the intake manifold and saw oil in an area that should be dry, my guess was a crack in the weld in the Valley Pan area... I had seen this once before,.. I pulled the manifold and there it was, a damn crack!!! About 10” long!!! So, if ya run this set up, and notice a Lack of vacuum but it doesn’t make sense, check this area out.... Gary G