Well let’s see where to start......
If you look at his pics, the after shots do not look to good; I see that his hoses and other rubber, plastic parts look spotted. This is not the look I am going for, so to me that is a bad start before I even read about how he was doing it. Next as Jnger said I wouldn’t SPRAY water on any motor, maybe I just know how an engine works, but I would never do it. Next he says to "Start the car and drive it around for a few minutes until the temp gauge is about halfway warmed up. Not fully hot. Pull back into the driveway or wherever you wash your car. Open the hood and absolutely soak the entire engine compartment with Armor All. Everything. Paint, wiring, engine, everything." I have sprayed "dressings" on metal and painted surface’s and it didnt work out to good for me, also in the same breath is the wiring comment, If you "absolutely soak " all the wiring this could cause a number of problems, even if the "dressing" you are using doesn’t short out any of the connections it will make all the dust and dirt stick to all of them, this also go's for all the "painted" and metal stuff under the hood. The "dressings" will not soak in to the Metals then dust and dirt will stick them as well. Then the next step he says to dry everything off, with a towel in the morning, which is good but you cant get it out of all the nooks, crannies… BUT! then he says to blow it out with a air hose, which in turn will blow dressing all over your windshield and fenders.
In my eyes I don’t think his way of detailing an engine is too good, but this was just my 02$
:nixweiss