Cub Oiling Problem

Just finished rebuilding a Cub engine and have been unable to get any oil to the oil filter. Checked pressure at the oil galley plug on the rear of the engine (left side) and measured 48 psi. I cannot figure out how the oil gets to the passage in the filter housing. Obviously it is plugged somewhere but can"t find where it is fed from. Any ideas or help would be greatly appreciated.

Tommy D6-8U

After a while I went back to it and found the passage leading to the filter housing. It is cross drilled between cyls. 3 & 4 from the tappet chamber through the main oil galley; there is a small pipe plug there.
It was plugged where it turned up into the filter housing. Cleaned and flushed it good and hope to get it back together soon. Thanks for your help!

This is the only Farmall that I've heard that does this. I think it's where the oil pump is installed at the rear of the engine. Most oil pumps whether on a tractor or car are connected
to the engine vertically and are submurged in the oil in the pan. Hal