96 nissan 2wd

I was driving down the road motor died heard a clinging noise put it in neutral and came to a stop tried to start it and nothing Towed it home Next day checked battery and fuses all were good. Checked oil in trans and motor all good Tested starter and it was good. I tried to turn the motor and it would not budge. Removed oil pan and ran into sludge but no metal shavings Removed valve cover and seen sludge on rack. Removed upper gear for cam and tried to turn motor But, still nothing!!! I looked at all the possibilities and am stuck between a rock and a hard place. Does anyone know or have had the same problem?????:confused::banghead:

timing chain...