as Rick said. a leak at the seam of the head and block.. that is almost categorically a head gasket issue. other problems may be underlying like a porus block, cracked block or cracked head.. but you will be pulling the head to check that anyway.. and that means changing the head gasket.. which is the first 20$ test I'd do on it after the visual inspection for flaws and flatness.
and that isn't specific to an N either..
With no oil passages in the head, and an external leak.. and no water in the oil, or combustion byproducts in the water, it makes it an even safer bet on the head gasket, vs a cracked head / cracked block...
I make no claim of any special knowledge on an N engine...
I didn't get ruffled
you , in your question, ruled out head gasket as a possibility.. thus i said I couldn't help you...
what use would it have served tellyou it was something you had already decided it could not be?
soundguy