There are people of all sorts who have cleaned their engine in many different ways. Many just spray on the degreaser, let sit and hose down, without any regards to ANYthing under the hood.
I don't see how that can be too bad a thing when you consider that the engine and its components are all in the open air and water splashes all over them whenever it rains and when you go over a puddle of water.
When it came time for me to wash my engine i bought a can of EngineCleen or whatever brand you like and first covered many of the engine'* important parts. Here is what I covered:
I TAGGED and removed the plug wires from the spark plugs and from the ignition coils. I didn't take them off of the engine but I just tagged them and wrapped both their ends in plastic baggies with a rubber band at the bottom. This would work same if you just wrapped them in some regular plastic wrap, just remember that the wrap may come off with the pressure of the water so do becareful. Then i removed the intake all the way to the throttle body (my intake hose has the MAF sitting in the middle of it). Then I wrapped the throttle body'* opening with plastic wrap and put a rubber band around that to hold it down. Finally I put plastic bag aroudn the ignition coils to keep them dry and I wrapped some plastic aroudn the various wiring harnesses that had now been removed (aka the plugs from the MAF, the air temp sensor), although this may not be necessary. Finally I baggied all the spark plug ends coming out the block.
Next I applied the degreaser liberally and especially on the extremely dirty spots. Waited a while and then hosed it all down.
It wasn't as clean as i had hoped but it was alright.
After it was all done I noticed the accelerator pedal was REALLY hard to push down. This was because the degreaser had degreased the accelerator linkage spring which is hooked to the throttle body. A little WD-40 fixed that right up. Also, I bought a can of Belt Dressing to make sure my serpentine belt was in good shape and to be sure the degreaser hadn't affected the belt.
If yours is like mine then your intake hose has a metal tube coming out of it going to the bell housing cover. Not sure if your bonnie has it but just make sure that if you do have it, and after removing the air intake hose the tube is sitting there wide open for things to go into it that you cover its opening too. Not sure what engine degreaser in the bell housing would do to an engine .... other than greatly increase the risk of loock up among the springs, pushrods, and valves...
Anyways good luck and enjoy. I might have gone too far with my protecting the engine but i don't know I just wanted to be sure. Oh and finally (i know i never stop !) i kept on smelling that engine degreaser'* vapors coming from under my hood for a good month or so after degreasing it. I guess I must have missed some crevices while hosing it down, make sure you don't, it'* not fun for one, and for two , degreasers are flammible!
-87 Bonneville (and Mike Diaz)