Stud replaced to spec, valves adjusted and sound persists with no change . Without digging further in, think I have a lifter that has started to wipe a Cam Lobe, the sound i think is from the valves slapping closed onto the head a tad earlier than they should. I swapped in a magnetic drain plug and I'm pretty sure I found metal flecks in the bit of oil that spilt out. Looks like the car is going in storage for a while until I can get a new cam/heads put in.