I dont think it's the oil , but that's a fair guestion.Pls elaborate on procedure. Does it matter where the lifter is on the cam profile?
Stock 1.5 stamped rockers.
Wondering if a change of oil viscosity might help?
What kind and weight does the engine have in it.
If it's some exotic synthetic light weight , who knows?
To my old ears though , it just sounds like a lifter or 2 bouncing around.
We have seen steel stamped rockets on here with holes clear through the rod cup, ect ect.
Just need to get those covers off and check all while its stone cold.