2003 Mitsubishi Eclipse Spyder 3.0 knocking bad till oil warm?

Okay, 03' Mits Spyder with 3.0, almost seems like piston rattle, it knocks bad, rev to 3k hold to 2k and she'll quiet right down, runs strong, no smoke..what gives?, doesn't seem like oil staying up in heads? Rest of day fine , just seems like if it sits over 12 hours or so with out a start.
Thank you