The low knocking is the clutch but the high occasional ticking is either a chain slap or may be a sign of a roller problem on a rocker. I suggest checking all the valve lashes and the condition of all the rollers...one may not be rotating-I had one. While there check that the cam chains have the correct tension and that there are no signs of odd wear on the sprockets. Also check the end play on the cams-shouldn't be enough to feel.