Spraying Down Engine Bay

Well my engine bay is kind of dirty.  I would like to spray it down, to help clean it up, but i have heard that if something gets wet (cant remember what) it can ruin it.  I dont need to have my engine running or anything do i?

Heres what you do.
Get a spray bottle of Simple Green (I use Simple Green Max)  Spray it on in the enigine compartment, and wipe it off.  For those hard to reach areas and places with built up road grime spray the Simple Green on it and let it soak for 5-10 minutes then use a garden hose and spray if off.  After that just dry up areas that got wet.  I did this the other weekend and my engine bay is still spotless.  Some may recommend using Gunk Engine Brite, but I personally only use that on the undercarriage since it is more harsh.  I wouldn't recommend using a pressure washer either, that can really mess things up.  The way I mentioned may take longer, but is the right way.  When it comes to cleaning this part of your car it is best to take your time.

The early OptiSpark are notorious for getting wet and dying.  In 1992 on the Corvette LT1, if the water pump went out, you had to replace the OptiSpark, although some were able to rebuild them.  It was impossible to change the water pump without getting the OptiSpark wet enough to die.
 
In '95, I think, they went to a vacuum-powered vent system that kept it drier.  As a result, the problem is much less than before.  In fact, I bought a '97 Z28 in September that when I went to pick it up, the water pump was dumping a tremendous amount of water out. A gallon roughly in about 20 miles or so.  As such, the OptiSpark HAD to be wet, yet the car still ran and ran fine.  However, a pump leaking that much had been leaking a long time and who knows how hot the engine had been and how many times, so I let them keep the car and cancel the deal.
 
So if you have a '95 to '97, the problem isn't as bad.  However, it is still best to not tempt fate and to not spray water around it.
 
Doc
 

Usally what you do is get a few peices of plastic, cover the battery, altinator & spark plug distibuter/coils.  Just to be safe.  Also cover your intake if needed.  Then get a bottle of degreaser & spray the entire engine with it.  EVEYRTHING, be generus.  Let it sit for about 10 minutes.  then get a hose
and wash everything off.  Then remove the plastic & your clean!

when u do wash it out u need to either keep the eng if it is hot or make sure it is cold to the touch cause hot metal and cold water dont work so dont drive around 4 hrs then go home and wash the eng out. the opti is a not wet friendly system so try to stay away from that with water but it personal choice on what cleaner u use but u really don't wantto use to high of a pressure washer i think u need more then just a granden hose but not a pressure washer that will cut ur hand either.

Good point Chevycowboy about washing temps.  I forgot to mention that I used an adjustable nozzle for the water hose to spray in light steady streams.

alright thanks a bunch, very helpful

Use a pressure washer.  I do all the time and have never had an issue.  Just be careful around certain areas.  Do you all really think that your undercarriage doesnt get wet when it rains?