How many miles since the last oil change? That sounds like a lot of sludge. I will bet there is just as much sludge in the oil pan. The oil pump in these engines is low volume and low pressure compared to more modern engines. This will lead to reduced overall movement of oil in the oil pan, resulting in heavier, dirty oil settling and remaining at the bottom of the pan whether you have an oil filter or not.
Carl
Now I'm more curious than ever to pull the oil pan and have a look/see.
Chuck
