How much time would i have to look into the sun to go blind?

Depends: Why would you do this? The eye will try and avoid the pain of looking at the sun and the pupil will constrict as much as it can to limit the damage. The eye will focus the sunlight on the most critical parts of the back of the eye and the time to have damage would depend upon light intensity (is it mid-day; is there smog?) and upon the steadiness of the fixation.