rmendoza - there are a couple threads on that here - but basically on the engine itself - elbow grease. Cleaners will destroy the factory finish. Here is one thread:
http://www.zr1.net/forum/showthread.php?t=10039
While some have done it - I personally will not get a water hose near my engine bay. Seen too many issues after someone washed in there - and some even if they were careful. "KILLSHOTS" is having an electrical issue right now after washing it even though he covered the engine with plastic.
I have cleaned my engine bay thoroughly with rags and various things (detail spray, Aerospace 303, etc) I did use a bit of Adams polish on the engine itself. My engine is the one thing on the car that I am not happy with it's cleanliness - but I can't afford to have it professionally refinished. I have won "best in class" at a couple shows so far with it as it is though so it isn't too bad. Just take your time with soap and water and rags - then dress the bay itself with "Trim Shine", Aero 303, or some other shine/protectant you like...