That really sounds like the chain has jumped a couple of teeth. Have you counted the chain links between the points on the sprockets that would confirm or contradict this? There aint no way a chain can stretch that much.
Purchased new in July 2006, 0 miles.
Miles as of January 2019 102,137 miles
Haven't counted it but camshafts are off and cam chain is out right now waiting on a new one, since its the last thing i could think of that'd be making the noise so will see if that was the issue when the part gets here next week.
Welp a different update but i won't be able to test that cam chain for a while, was watching videos and realized copper flakes in the oil pan means crankshaft bearings are going and well...... they are, so I have to split the crankcase.