Flushing an engine can be like retrofitting modern oil to an engine that has had non-detergent all it's life. A lot of stuff can be kicked loose. As an alternate suggestion to flushing whatever down into the engine oil pan, how about an engine oil pan and valley pan removal and then flush with kerosene? Oil lines can be flushed also with the oil pump removed. This not being a recommendation, but, with severe sludging this might work. At least a visual as to what the extent of the problem is will be more evident. Warren Anderson Sedona,AZ