Yes- - - -small port is a drain back into the oil pan, with no pressure on it. With the dowel in the "out" position, both of the large ports receive the output of the oil pump. Either one could be used as a supply point to the bypass filter, with the return line going to the small port to the left of the lower 1/2" port.
Once the dowel is pushed in, the lower big port becomes the oil filter supply point, with the filter output going to the upper large port and from there to the engine. That puts the filter in series with the entire flow of the pump and the drain back into the pan is not used. If the engine is run without a filter and the "full flow" dowel is pushed in, a jumper line between the 1/2" ports MUST be installed.
I have a late model 261 engine in my shop. I'll look at the plumbing ports and confirm that I've got the flow visualized properly.
Jerry
Last edited by Woogeroo; 03/02/2015 1:14 AM.
