crank throw scuffing the oil pan? this happened to me once on a Rambler six, a seemingly-insignificant dent on the pan caused a crank weight to scuff, made a terrifying sound on a new engine.
if none of the usual suspects are causing it, a stethescope might locate it. my father (g*d rest his miserable soul) used a long screwdriver for that; handle on the bone behind his ear, tip on suspect location. surprisingly precise.
