Hey Merlin......it works great! I just started doing it myself...
this was the minvans motor with armorall tire foam

now that is an engine cleaner

Yes tire foam works good but over time it collects dust and dirt so you have to redo it(wash and refoam)every few months.

That gunk was what I used the first time i used a chemical. Work nice, but these chemicals don't do everything. A good brush set, and armor all wipes do well!

I have always used the Gunk product. I warm up the engine, spray it... let it set for about 15 minutes and then go to my local high pressure car wash place, open the hood and blast away.

In the above statement, there are two things you are not supposed to do:
1) Run the car after spraying with Gunk.
2) Wash the engine in the car wash.

And I never cover anything. Everything under the hood is designed to get wet. In fact I often open the hood and give it a bath when I am washing the outside of the car. I do like to drive it a while afterwards to dry it out.