Motherboard and Overclocking

I had a question that regarding my P43 motherboard which the listed spec for FSB is 1600mhz. I had e8400 which I overclocked to 3.6ghz with 400mhz x 9 multiplier. As the FSB = 400 x 4 = 1600mhz, does it means that I can't push my oc further anymore? I know a lot of people out there could easily oc the e8400 over 4ghz.

You should be able to push it well past 1600. I had a P43 board that was spec'd to 1600, and I ran my E8400 at 3.8ghz 24/7 for 18 months without a hitch.