If you own an LS3, particularly one fitted with GM 0821 cylinder heads, there is one issue worth knowing about: valve seat failure. What can start as a relatively small problem inside the cylinder head can quickly turn into major engine damage when a valve seat comes loose and drops into the combustion chamber. We recently had an LS3 come into the workshop after suffering exactly this type of failure. Watch the Full Video Breakdown In the video below, we explain what happened