Rough Idle Problem- 1967 Valiant

Pull the PCV valve out the valve cover and throw a thumb over it. Now does the engine run below 1,500 RPM?
Second that. I recently couldn't get my 1965 Dart w Carter BBD to keep running, no matter how I fooled with the carburetor. Finally found the PCV valve at the valve cover had a massive vacuum leak due to a rubber grommet which had fallen apart (Chinese rubber).