Reply To: Bypass Oil Filtration 1931

[Randy Roberson]

An update to my investigation of the bypass oil filtration issue:

I examined the copper piping which served as the oil inlet and outlet on my ’31. There were no orifices, only normal brass tube fittings. I then checked the filter element: an AC P-21 painted blue with red logo, etc. and stamped INLET and OUTLET at the appropriate end. I poured thin solvent into each end and it would flow freely into the filter at the inlet port, but I could get practically none to pass into the outlet port. Then I poured about two cups into the inlet; after a few seconds passed the oil-solvent mix began to dribble out the outlet port. I turned the filter over and oil would pour out the inlet port. It became clear that the filter itself has a restriction on the outlet side.

Next I plan to cut the filter open to see what’s inside.