still sounds like some bad lifters. Start it up and its fairly quiet then it starts to clack up top like a lifter. Rev it up a bit the gauge goes up and after a while the clack goes away like it got enough oil. Let it idle again and the clack comes back. When you hold the RPMS up there is no nock at all, I had a big block blow some lower bearings and it sounded like a diesel when you put some rpms to it.