I know Nic knows more about vehicles then I will in my life so I hope he is right! What actually causes it seems bound to shorten engine life to me. GM says there is no problem so if ya got it, your stuck. It is actually the piston skirt striking the cylinder wall. Too much clearance between them. As the engine warms up, the metal expands reducing the clearance and therefore decreasing the GOD-AWFUL racket. I have read that LS1's have noisy valvetrains too and may contribute to the overall noise. Either way, it sucks. I have had friends/co-workers razz me when they hear it start up. "Got any oil in that thing?" I don't think the problem was strictly an LS1 problem either. If I knew how to post a link I could put one up explaining the whole deal. Go to MSN or Yahoo and type in GM piston slap. It sounds reall scary to me down the road!
