I just got done cleaning a full flow canister, just pulled it the other day. The filter was heavier than any I could remember and there is about an inch of thick crud in the bottom of the canister. It is soaking right now to get the sludge out of the canister. I haven't got to the oil pan yet. The rocker shafts were open and there was not an excessive amount of junk on the head or rockers. My thinking is that these filters may not be to space shuttle standards, but they appear to do some good and collect a lot of sludge.
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
