I know what you mean. I had a Bailey dump valve on my Escort cossie, and didn’t like the possibility of debris being sucked in at idle or the very loud woosh either. I bought a Graham Goode Group A Dump Valve, Part GGR 110, http://www.grahamgoode.com/cosworth/frparts.htm that has a filter around it, and is a lot quieter. Hope this helps.

Cheers
John