Diagnose this whacking noise!!

[radcon]

I replaced the plug wires, cap and rotor today. Started it up afterwards and heard a weird whacking sound, actually I've heard it a couple times this past week when the car is cold. I actually had some time tonight, so I laid under the car and tried to find the source. It's definitely not rhythmic, it sounds like metal hitting metal and it sounds like it's coming from the underneath the passenger side of the engine. Definitely doesn't sound like it's inside the engine - it's too apparent and clanky, if that makes sense. Once the engine is warmed up, it goes away. I'm thinking if it's inside the engine, it would be more muted and would be more rhythmic. Hoping that some of the masters on this board can help me.

[WERK I]

Find your local NAPA, Pep Boys, AutoZone..., etc. andbuy a stethoscope. You will be amazed how quickly you can track and isolate a noise. Let us know what you find.