High Pitched whine

[Gandi69]

Just backed the 182 out of the garage, had a high pitched whine almost like an electrical buzzer on constantly. Sounded like it was coming from the alternator so I started slackening the engine cover bolt closest to the alternator and strangely then the revs dropped slightly and the noise went? What could cause this?

 

[Gandi69]

Think this must have been its retaining bolts distorting the inlet manifold joint very slightly, creating a the whistle and the high idle. Seems ok now, so Ill do a gasket change and do the plugs too.