sounds like what my motor did when it went, i spun a bearing and it was making that sound
sorry to hear man, if you decide to tear into it ill be down to lend a hand or two. even if something had debris on it when the motor was put together and it finally dislodged itself if it got between the bearing and cam/crank its going to spin a bearing just because your dealing with clearances of 1000's of an inch.