Well guys the "White Whale" is very ill, engine time......
If it's sludge and debris makes me wonder what the lifter valley and under the valve covers looks like.
Seen an old ford Windstar minivan that both those areas where caked in dry hardened sludge/ varnish. Had to be opened up and vacuumed out then flushed and the pan pulled and pick-up replaced. Ran good after that again but nasty stuff.