I traded a BMW 530i and a GSXR 600 for a 2002 C5 today. Has a bad trans slip that I can fix at a shop sure, but about two hours of ownership it starts to do a little tap im thinkin its just some loud lifters I'll do a oil change tomrrow. Progresses to get louder and louder and now it sounds like something is loose and broken, I dont even know what it needs.

Video:
Update: Pulled the dip stick and there was no oil. Put 5 Quartz in and its a smidge over filled. The oil pressure gauge is broken so that explains why there's no warning light. I put oil in and now it sounds better but still a slapping/rattling noise. Im thinking push rod for the squeak and lifter for the thud. I took the valve cover off and inspected the rockers but they all seem tight on the jiggle test. 6/8 of them move side to side though.
Update:

 

Welcome to the forums. Yes it sounds bad. But it sounds external like something in he Harmonic Balancer front pulley area. Take the serpentine off then start it and see if it sounds any different.

 

Its coming from either the valve train or the bearing that the piston connects too. Im assuming the squeak is coming from a push rod and the thud is a lifter?

 

Ok my second guess is something like a bolt is coming out of the flex plate giving it that clunking knock and scraping sound. I would pull the flywheel cover and take a peek. Doesen't sound like a rod or main bearing to me. How is the oil pressure?

 

Not a trans issue or flex plate. Sound is coming directly from piston two. or maybe bearing clunk is echoing idk. Might just get some performance rods and lifters and see if that fixes it.

 

So that leads to eather it's broken piston or a bad bearing or maybe a carbon knock if it has been run hard recently and knocked some carbon loose and is hammering on the cylinder head. a cylinder scope might be a good thing to have for that to inspect the top of the piston through the spark plug hole. A Carbon knock can sound just like a bad rod bearing.

 

im rlly thinking its a spun crank bearing. i showed the video to some performance shop around me and they said it was rod knock. car was running without oil for sometime so I think im just going to get a used ls1 and drop it into the corvette when I have my truck finished. or i do a crankshaft job that costs more than a ls1 swap

 

Maybe its time to freshen up the engine, and the transmission to. Let us know what you find out.

 

Welcome to the forum and the Corvette hobby. Good luck and let us know how it turns out.

 

If was my car I would order a Crate engine from Summit or Jegs and start fresh. Internal rattle noise is never good. Low oil level and a nonworking oil pressure gauge is a Red Flag. This is a good example to have a mechanic check it over before you buy when you don't know the history on a car.