Engine bay cleaning....

[BongoCaterham]

What's the best way of cleaning an engine/engine bay???

[Golf Juliet Tang]

I wish I knew.

[Shaun_E]

You need a good degreaser. I'm pretty sure that the engine builders use Jizer but it's horrible stuff so avoid getting it on your skin. It's used a lot in parts washers.
I've used the Halfords heavy duty degreaser spray with reasonable success on smaller engine parts using a scrubbing brush.