Is it normal to have a slight knock at start up and high RPMs ? Mostly makes the sound from cold start and goes away.

 

RPM's kinda not,but ls1's are known for cold start knock.

 

Depends, I had something similar to that, I actually have a video clip you can watch and listen to. Anyway I threw 2 rods later on, it lasted awhile but they let go after doing 7400rmp dyno runs and then going to the track the next day, 2nd pass it happened.

-Sly

 

Sounds like piston slap. Mine doesn't have it, but I've heard of a lot of earlier LS1's having this problem. They "improved" the stock piston design on later models to help with this.

 

So if it is piston slap am I doomed for a shorter engine life?

 

not nessesarly.My 02 ss slapped from 8k till 40k when I sold it.I sprayed the **** out of it to.