In a little over 65 years of tinkering with engines of all types, I have never seen a bypass type filter canister that did not restrict oil flow by some means- - - - -usually with a small hole in the standpipe. One notable exception was a spin-on filter that was used on an American Motors flathead six- - - -the filter base had the restrictor built into it. The only time I've had to add a restriction was when using an aftermarket spin-on filter bracket in a bypass situation. That's where I used the Holley carburetor jet in the inlet fitting to the adapter. One restrictor is sufficient, no matter where it happens to get placed in the oil circuit- - - - -before, after, or in the filter element itself. Line diameter has no effect whatsoever on pressure.
Jerry
