I guess the gauges/manifold might be bleeding gas somewhere, but they were able to hold a 28-29" vacuum with schrader valves closed. I heard earlier from my buddy across town who owns the car. He said after the pressure increased to 40 psi when he warmed up the engine, it had dropped only 1 psi...

This about a brand new Vintage Air R134a system in a hot rod. I used a small Robinair vacuum pump to pull down to 28"-29" indicated. When I close the manifold valves, the vacuum slowly drops, around 1" every few minutes. So, I decided to see what it did with pressure. I statically cha...