overclocking i7 920 CPU- what can i achieve?

Okay after following a guide on youtube i've managed to achieve 4.0 ghz although I'm wondering if I can go higher? as my temps are only @ 40oc and what I'll need to change in the BIOS to achieve it. All help would be super appreciated !


CPU: i7 920 d0 chip

CPU cooler: Cooler Master Nepton 240M Liquid CPU Cooler

RAM: G.Skill Ripjaws X F3-12800CL9D-8GBRL 8GB (2x 4GB) DDR3 1600MHz Dual Channel Memory Kit -

Mobo: ASUS p6x58d-e



EDIT:

Managed to get 4.4ghz without hyperthreading @ 65-70 temp max load if anyone has any suggestions let me know

Here are my current settings



* Ai Overclock Tuner.....................[Manual]
* CPU Ratio Setting......................[21.0]
* Intel(r) SpeedStep(tm) Tech............[Disabled]
* Xtreme Phase Full Power Mode...........[Enabled]
* BCLK Frequency.........................[210]
* PCIE Frequency.........................[100]
* DRAM Frequency.........................[DDR3-1683MHz]
* UCLK Frequency.........................[3368MHz]
* QPI Link Data Rate.....................[Auto]
* CPU Voltage Control....................[Manual]
* CPU Voltage............................[1.39375]
* CPU PLL Voltage........................[1.80]
* QPI/DRAM Core Voltage..................[1.25000]
* IOH Voltage............................[1.14]
* IOH PCIE Voltage.......................[1.50]
* ICH Voltage............................[1.20]
* ICH PCIE Voltage.......................[1.50]
* DRAM Bus Voltage.......................[1.64]
* DRAM DATA REF Voltage on CHA...........[Auto]
* DRAM CTRL REF Voltage on CHA...........[Auto]
* DRAM DATA REF Voltage on CHB...........[Auto]
* DRAM CTRL REF Voltage on CHB...........[Auto]
* DRAM DATA REF Voltage on CHC...........[Auto]
* DRAM CTRL REF Voltage on CHC...........[Auto]
* Load-Line Calibration..................[Enabled]
* CPU Differential Amplitude.............[800mV]
* CPU Clock Skew.........................[Delay 300ps]
* CPU Spread Spectrum....................[Disabled]
* IOH Clock Skew.........................[Auto]
* PCIE Spread Spectrum...................[Disabled]
* C1E Support............................[Disabled]
* Hardware Prefetcher....................[Enabled]
* Adjacent Cache Line Prefetch...........[Enabled]
* Intel(r) Virtualization Tech...........[Disabled]
* CPU TM Function........................[Enabled]
* Execute Disable Bit....................[Enabled]
* Intel(r) HT Technology.................[Disabled]
* Active Processor Cores.................[All]
* A20M...................................[Disabled]
* Intel(r) SpeedStep(tm) Tech............[Disabled]
* Intel(r) C-STATE Tech..................[Disabled]