i was thinking about liquid cooling for my q6600 and was wondering how wxpensive would it be if i made it and bought all the parts. i would want it to go to at least 4ghz. are there any limitations with OC q6600 like a point where the mobo limits it or somthing. i have a d975xbx2 mobo 975 chipset if it helps.
would i need to Liquid cool my chipset too?

You might want active cooling for the chipset at the minimum. But the real limit will be your mobo and how high of a FSB it can handle. The chipset is a high end so it would be pretty high but might not hit 444MHz which would get you 3.996GHz and 445MHz would be 4.005GHz.

Good luck, I suggest you google your mobo and OC results to see what the top end is for it.

That chipset will not do. You have to buy a new motherboard for 4ghz. P35 and 780i can reliably oc to 1600mhz (4x400) fsb. Some people have gotten them to 1800mhz, but it's shaky. Your only dependable choice is X38/48, which runs at 1600mhz fsb natively and reliably oc to 2000+mhz.

I've done just above 4ghz on Q6600 on air cooling. Temp stablizes at 70 (sensor reading 70/70/68/68) degrees C after one hour prime95, which is high, but acceptable. The real problem is not temperature but vcore. I had to run it at 1.65 to get 4ghz, which is just too high. Tuned it down to 1.43v at 3.6ghz for day to day operation.