oil pressure on WD

I think I know what the problem is but I have no solution. In the base of the oil filter mount, there is a large "hole" that drains the oil back to the pan. There is nothing I can see to direct the oil up through the filter instead of it just running back into the pan. It appears to me to short circuit back to the pan instead of going through the filter which would create a restriction and cause a back pressure. Am I using the wrong type of filter? Or am I just all wet in my theory? Would really appreciate anyone's help? Sorry this is so long.

Also, when I worked on the relief valve for a WD, it was very difficult to get sufficient pressure on that spring. If you can get the screw in easily, oil pressure will be low. I had to use a lever to hold that plug in position while I turned it in to get mid scale pressure (about 10 psi). As I recall, it took two people. If the engine is out of the tractor, it is much easier to install this plug. To increase oil pressure, just add washers inside the plug before installing the spring. Put in as many washers as you can and still get it together.

Here's the dimensions of that tube. I copied this info from a post here at YT some time ago. It is for a B but I think yours would be the same. The top of the tube has a rounded (almost spherical) end so it doesn't snag on the packed filter media when installing the filter. I would guess that a short piece of brass rod with a 0.118 dia hole down the center, rounded over on a grinder and fitted to plug the upper end of a piece of copper tubing would work fine.

AC-B Oil Filter Tube Dimensions:

It is 1/4" OD tubing. It is 3 3/4" long (above the extended base) The hole in the top is .118 Dia. 1/4" down from the top is the center of a hole .085" drilled through both sides.

There is no seal at the top of the tube the flow resistance comes from the packed media itself. The tube serves to force the oil to start at the top of the filter and flow down through the packed media to the gravity drain that goes to the oil pan. Just make sure you use a filter that has packed media. The NAPA 1101 (WIX is manufacturer) no longer has the packed media and results in an oil pressure reduction. As far as I know, the Fram C159 should be fine. You do need to have that tube in order to 1) get filtration of bypass oil at all and 2) to provide the backpressure from the filter media in order to achieve the designed oil pressure.

Rod