Umm....no, ALL the oil won't bypass the filter but some percentage does....it would all bypass if the filter was somehow totally blocked though.....it splits the hydraulic circuit, most goes through the filter but some bypasses. I thought that it was as you said until I sprayed water down it while cleaning the block. My question is what was the original purpose? Is it another hold-over from the Poly (like the lifter bore angle?)

I'll put the plug in but I'm just curious if they used this bypass (for whatever reason) in the later Hyd roller blocks.