351W with Explorer front dress and valve covers. I ran a hose from the barb on the filler neck to the center port on a 1406 Edlebrock carb. I noticed when I shut the engine off, I could hear a hissing sound coming from the carb throat. I started it back and unscrewed the filler cap on the valve cover and the engine died. Got my remote starter and with the cap off the filler neck I tried to start the engine, would not start. I then placed my hand over the filler neck and the engine started and was pulling a lot of vacuum against the palm of my hand. Should I put an inline PVC valve or some sort of orifice in the hose? Should I vent the other valve cover?