From David R:
Take it to a Quarter CarWash (which isn't a quater any more). Use the Rinse cycle at low power and get the engine bay completely wet. Then spray Simple Green generously in the entire bay. Immediately rinse off. I use the high pressure Rinse but you can use the low pressure also.
The only thing I cover is the K&N Filter. I have never hand a problem with the computer or distributor although you must have good wires that seal. (I use ACCELL 8mm).
I just uncover the K&N and run the engine. The whole engine bay looks brand new.
From Bob Tom:
I too use Simple Green. Don't have to worry about it and bad effects on rubber. I remove the air cleaner, cover the throttle body with a plastic bag, cover the computer and its 3 connectors with a plastic bag (more of a safety precaution), spray using the Simple Green bottle with nozzle set at FOAM, allow to stand for 3-5 min., spray with garden hose and spray set at wide spread. Any heavy duty oil can be wiped off with an old rag. Use the air compressor and spray most of the H2O off (especially around the distributor and spark plug wires), reattach everything and run at idle until rest of water evaporates.
From Jon Steiger:
A caution to those of you using Simple Green: it will etch aluminum and speed
the corrosion process. The aviation community has known about this for some
time; most airplanes have a large percentage of aluminum in them, so most
pilots steer clear of Simple Green for this very reason. If you use Simple
Green, be careful with the aluminum parts in the engine bay, such as the A/C
lines, heads (for you 4.7 folks), etc. The Simple Green should only be allowed
to sit on an aluminum part for 10 minutes at the very most. Be sure to
thoroughly rinse everything afterwards. In case your're the skeptical type,
you don't have to take my word for it, check out the FAQ on Simple
Green's web site.