LS2s (and LS engines in general) are notorious for the sewing machine-like valve train clatter. Are you sure it's a new sound?
That said, I have heard a lot about oiling issues with LS2s - primarily oil pumps giving up the ghost - so it's feasible something could be going on.
Can you give more specifics on the sound? Does it sound like one valve tapping or is it a consistent clattering? Louder/more frequent with more RPMs or always the same?
|