General Maintenance & Repairs - What is this noise?????

This noise started this week. Any ideas on what this could be? Lifters, rod, exhaust leak???? Any suggestions are greatly appreciated.

http://youtu.be/tG90TsCnIlM

http://youtu.be/Xd_q0tlqD4k

Sorry bud, that's a rod knock.

Could it be anything else? I noticed today that the knock goes away when the engine is warm.

idk man that sounds like a very distinct rod knock. or you got some serious piston slap going on.

I have an 01 TA LS1...first I have very low oil pressure at idle....goes up when I accelerate and drive...everything is fine then maybe after 30 mins I hear a knocking type sound....can you guys give me some advice/suggestions? Perhaps a weak oil pump and not shooting the correct amount of oil in and not lubricating lifters? Like I said it drives perfectly for a couple of mins then the noise starts. I'm no mechanic but would like some fellow TA owners advice/suggestions. Thanks for your time guys.

What's your psi at start up? Before you start tearing the motor down I'd hook a mechanical oil psi gauge to it first. It's normal for the psi to go up during acceleration.