Generally OCing on the stock HSF is a bad idea. With my stock Intel HSF, my stock speeds had my cpu going into high 70s at load. I got the Zalman in my sig, and at stock it never went over 45. Now even with my OC, it idles at ambient, and at load only goes into low 60s. So, long story short, I'd say you MIGHT be able to get a tiny OC on your stock fan, but I wouldn't advise it.