Good work Grease. There seems to be a great lack of consistency in trying to apply what you learn from one number to another. I have compared the PF 1177 to STP SO2856A, Purolator L10193, Hastings LF 143, ST 3950, and Fram PH 3950. None of them even came close to it. However it only had 255 sq. in. area, and a later version even less. That PF 1218 sounds familiar. With no bypass to sweat, if it has the same 20 mm thread and the gasket fits, I might try one if my local Advance Auto has it. I may even look at an ST 5. I have mostly used the ST 3950, since it is cheap, in stock, and about as good as the rest except AC.
I am not sure the inlet and outlet holes are that important. I think they are large in comparison to the oil galleries. I would need to look at the equations for holes, but for tubes, the flow is proportional to the fourth power of the diameter, a tube twice as big will have 16 times the flow at the same pressure. Fewer, larger holes with the same area would have more flow.
