Interesting day with the stethescope.....
My boss drove his 95 L67 Riviera to work today for me to diagnose an idle rattle and whine with my mechanic'* stethescope.
The diagnosis on his car is the rattle at idle is the SC coupler, and the whine is probably one of the idlers.
While we were at it, we did some comparisons to my car. I've been noticing what I thought was lifter clatter the last couple months. We attempted to narrow it down to a particular lifter, but whenever we put the stethescope on the heads or valve covers, it was dead silent. Good news.
Tracked the noise down to the Alternator. Odd that it'* a lifter-clatter type noise, and NOT on the rear as I would expect. It seems to be coming from the front bearing. All brackets are tight btw, and the alternator is running fine electrically. This is one to watch, but also a good reason why a $10 mechanic'* stethescope is worth it'* weight in gold.