There are two filters made from filter foam. The first pic shows the location of the filter that blocks the opening to the oil pump area.
Cut a cube that is a little bit larger (height and width), poke a hole through the center of it so the manual pump rod will slide through it and trap the filter in the channel centered under the screw boss just above my finger in the pic. I haven't made that one up yet but I think about 5/8" - 3/4" long and snug in the channel. Just make sure it blocks off the opening when the oil pump area cover (piece of aluminum held on with 4 screws) is installed.
Nothing precise, just plug the hole
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This is the filter foam that slides through the opening in the front of the oil pump. Make sure it doesn't touch the pintle (the button with the shaft and spring that goes into the center hole).
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