Loud noise---Please Help

[Blu]

Just when you get one problem fixed another rears its ugly head...

I was just reading up on the temp sending unit in my car since my temp gauge
isn't working and after cleaning the connection and reassembling I decide to
take it for a test drive.

As I am driving the car around the block to get it heated up, I hear some
god awful noise. After a little bit of examining...I was able to
observe---that it happens when I am accelerating or when I am in neutral and
hit the pedal fairly quickly...somewhere around 3200-4000 rpms. Another
thing I noticed is that the lights brighten when the noise occurs. I am not
too sure where the noise is coming from but it sounds like a fan slip but
much louder and more violent---like something is hitting something else
(metal on metal screech?). It could be my imagination (let's hope) but there
seems to be a faint metallic smell right after the noise sounds.  Another
point is that the noise happens once per acceleration or throttle hit and
last for only a second or two at most. Although it happens fairly regularly
it does not happen every time.

What is this? Do I even think of traveling with this car over Thanksgiving
Day?

TIA

Blu
'88 80q

PS--BTW I think I need a new water temp. sender as the gauge only responded
for a few minutes before returning to C. Do they really cost $40?
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