need some help on overclock

[imported_xeno]

hi i am currently trying to oc my c2duo e6850 3ghz

my setup is
c2duo 3ghz
asus p5k-e wifiapp
g.skill 4gbz @ 4-4-4-12 2T
evga 9800GTX + 512mb
550watt earthwatts psu

my cpu is cooled with corsair liquid cooling
my temps right now under load are 30-34C

i oced it to 3.4ghz without upping the voltage
the ram i didnt touch anything

can u guys give me some advice i wana try hitting 4.0!!