Well i hear this (pully sounding noise ) like its rotating very loudly coming from the engine bay...i took off the The belt and still heard it... My buddy said it sounds like a bad lifter but he says its moving to fast to be a bad lifter...he then suggested Forged pistons have similar sound to them... This is my first camaro so I dont know....Ive talked to other F-body guys and they said it sounded normal to them....i dunno

any info

 

mine was the same way but it turned out to be the lower rod end bearing so instead of paying to fix it i just bought another motor but thats what mine sounded like and i took it to 3 different mechanics and they all told me that it was the same thing. well i hope that will help you out.

 

Judging by your name its an Ls1. So, its an alimunum block and you're going to hear more.

If people who have been around the LS1 says it sounds normal then I'd imagine it is.