So, I have a generic sandwich plate adapter that I'm going to be using for my oil cooler setup. I'm planning on drilling and tapping that and installing my oil pressure sensor and oil pressure switch into the sandwich plate. My question is, does it matter which surface I drill out? Obviously, the tapped sections are going to be on the outer surface of the plate. What I'm concerned with, is which surface is the in/out on the adapter plate? Does the oil flow from the center of the filter, through the filter, return through the outer holes? Or the reverse? (returning through the center of the plate?

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Anyone?