I have an old Sierra that I was using as a winter hack when the engine became very ill. The engine still ran but would stall if you let it idle, made a horrible racket and was chucking out loads of blue smoke. I have been stripping bits off it today before it goes for scrap. This was the state of the timing chain, I cannot believe it was actually managing to run in that state :shock:
That cog at the bottom of the picture is the chain tensioner sprocket, its teeth have been stripped off, the chain has jumped off the sprocket and started to mill away at the engine block. There should be a chain guide on the righthand side which seems to have vanished though I did find a couple of broken bits of plastic floating around.