If it were a rod end cap/bearing failure you would know about it as the noise would be very noticable and the rod would more than likely snap if you reved it hard enough.

It is probably the area around the little end pin not the pin itself. Maybe it has run dry of oil and f**ked itself. Ive seen an engine before that blew the head off the rod cap bolt, causing the piston to travel further up the bore an touch the head and valves (this was not known at the time). It went to an engine tuners for an opinion (Hitec in Cradley) where he revved the balls off it and blew it up on the spot, not good