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Does anyone know how much gasoline expands into gaseous form when it explodes?
I know that nitrogen expands 700 times, and that water expands 1800 times when it becomes steam

when it explodes it is both oxidizing and changing phase, not to be confused with just becoming steam.

yeah hehe, how meany times bigger is the volume of that gas compared to the volume of the gaseline before egnited ?
i need this to a school project and i cant seem to find anything when i google after it =O

Why don't you calculate it yourself? Just getting an answer will not help you get anywhere.
Here is some help getting there:
1) What is the chemical reaction products in the combustion? How much energy is produced? http://en.wikipedia.org/wiki/Gasoline
2) Use the ideal gas law to get the expansion figured out.
3) Make reasonable assumptions for stuff you don't know.