[Christ]

Originally Posted by greasemonkee

I was cleaning some injectors with my homemade vacuum injector cleaner and carb cleaner not too long ago. I realized the gasoline present inside the intake manifold is probably boiling under normal operating temps, this was after I witnessed the carb cleaner exiting the injector went from a spray pattern to a mist once the vacuum exceeded 15 in/hg

It's a little different in an intake manifold... engines aren't really ever under vacuum, because there is always air going in. The "vacuum gauge" is just giving you an idea of how much pumping is going on, or what you would feel/see if air were not present in the manifold.

Under conditions of true vacuum, yes, the fuel would boil and vaporize instantly, and it may partially do that in the intake manifold, but because of the quantity of fuel and the inflow, it doesn't happen fully, which can be evidenced by burn pattern analysis, which shows that fuel actually pools around the crevice areas of the combustion chamber, such as the gap between the piston and the cylinder wall above the top compression ring.