Be careful with any Gunk Engine cleaner or Gunk Foamy Engine cleaner. It can be damaging to your pain in the bay.

I actually used Gunk and a steel wool pad to remove my engine bay paint before repainting it. When I did my motor swap, I took the time while the motor was out to completely strip the bay of all hardware, wires, lines, etc. then stripped the paint down to the factory primer using just Gunk and steel wool. After that I primed and painted it with High Temp Engine Block paint (low gloss black) and it looks great.

The engine bay was really nasty before I swapped the motor... the guy that I bought the car from never took care of it then blew a hole in his block so there was oil and dirt everywhere. I initially just wanted to clean it out but after the Gunk started stripping the paint I said what the hell and went all the way... looks good though, I'll post before and after pics later when I get home.