I have to suspect that there is a poor connection in the regulator leading to something moving to create the whine. A duff regulator is my conclusion, in short. But the conclusion is tempered by the fact that I thought I had seen all possible oil leaks until the day drops of oil appeared on the outside of the glass of my speedo!!
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.