Well, just seeing what you guys think. For the past few months I've had an odd issue. If I really floor it on takeoff, accelerate very rapidly or otherwise get the RPMs up too high, the next time I turn my car on I get a grinding noise under the hood from the passenger side of the engine bay. I figure it's a bearing somewhere, but not sure. After I drive a little bit, maybe a day or two (or sometimes less), the noise will just go away and won't come back. All I can hear now is some belt squeal when the engine warms up.
What kind of a noise just goes away on its own?

oh wow, normally when a bearing goes, the noise does not go away. id really have to hear it to be sure whats going on.

Yeah, which is why this is a bit of a head scratcher. If the noise comes back I'll get a recording of it. Also, it goes away while driving, not when turned off. Like I'll be idling and then CLICK noise gone. And it'll come back with a heavy enough foot. But, I don't like to test it... On a somewhat related note, the serpentine belt on the 7a is fairly simple to change? Is there an adjuster nut on the alternator or something?

Pull the accessory belts and check the bearings on the pulleys. Duplicate the conditions which create the noise, pull the belts, try to make the noise. It could be something inside the timing covers. Hell, it could be something in the top end of the engine loose.