Get a better CPU cooler. Read some reviews for LGA1366 coolers.
With a good cooler, you'd be looking at more like 3.6-4.4 depending on your ability and quality of the chip.
Also jumping 333Mhz probably wont be noticeable enough to warrant the extra heat, 2.6 to 4 is a different story though.
If you follow the guides, using Prime95 Small FFT and RealTemp for testing, you could just keep bumping BClck and see how high you get before the stock cooler lets things get to warm. You don't need to jump 2.6 to 3.0, start with 2.75 then 2.8 then 2.9 then 3.0 etc until the temps in a small FFT torture test get too high (keep below 70C, I prefer high 50's/low 60's).
No point asking really, just give it a try. Personally I'd get a better cooler though.