fuel evaporation & injectors

[d houlton x0710]

Robert Harris wrote:
> 
> One very simple thing to make life very easy.  If you can the piss dribble 
> injector stream directly onto the intake valve, such as by locating the nozzle 
> in the valve pocket, then you have magic.  It seems like the back side of the 
> valve averages about 600 F or more depending on load.   This should totally 
> vaporize and keep vaporized the fuel.
> 

So what's the temp at which the fuel/air mixture will spontaneously combust?
600 F seems awfully hot.  Is there any danger of the fuel exploding instead of
just vaporizing?

--Dan