I find that these products are great at removing light grease but aren't too effective when it comes to super heavy and thick gunky built up oil and grease.
There must be something, or at least some way of cleaning all the gunk....
NAPA carries a heavy duty degreaser designed for industrial equipment. I usually cut it 50/50 with diesel. Spray it on, let it soak and use a steam jenny or pressure washer to remove. Repeat until clean. It works much better than brake cleaner since it doesn't evaporate in 2 seconds which allows it to soak into and cut the grease.
***Edit - If you're talking about an engine that is removed, have it hot tanked. Just make sure the machine shop that tanks it for you is capable of making you a new bushing.
Gunk and then powerwash....if you don't have a washer try coin operated.....always kept my engines clean.....Go to searchsite and type in powerwash,there's acouile of good threads.....castrol superclean....my .02
Simple Green barely diluted .. if at all. And a good brush.
Side note: simple green tends to "evaporate" fairly quick, even on a cold motor ... so I usely spray it without being shy, and let it "soak" for 5 minutes, then spray again , wait 5, spray again, wait 5, then brush where it needs, and hose down. And I hose down for a sloid 5 minutes. Always keep the stream moving from one part to another, don't let it sit in one spot to long. Like a sweeping motion or something.
Thats what I do, and it works really well.
For plastics, wipe down with VinlyX, it's a great "dressing" agent and doesn't leave a greasy residue or come off with heat.