My 350 is making a strange sound (kinda like a knock, but not quite) I flushed the oil system yesterday, and the noise got a lot quieter, but it is still there. I am guessing that I probably have a lifter issue. Here's my question: After the flush, I decided to pull the oil pan. I didn't find any pieces of metal in the pan, but, at the bottom of the pan was a silver-grey sludge, with gold-colored (I'm guessing from bearings) flakes. It looks and feels like the grey sludge is a very fine powder of metal. Now, I am certain that the the pan on this thing hasn't been pulled since the engine was rebuilt (I'm guessing that was about 50k miles ago), and there have been a few modifications to the engine since then. New heads, camshaft, etc. Is the sludge a normal occurrence? I can't say that I recall ever seeing this before, but, then again, I haven't pulled an oil pan off an engine for at least 10 years.