If you have your BIOS settings for the memory section set on Auto, that is probably limiting your over clock.
If your memory settings are on auto, your memory is probably running at (2.65/1.86)*800 or DDR2-1140 speeds.
You need to find a setting gives you a memory clock twice the FSB freq for an FSB:RAM raio of 1:1.
i have tried that too. i even tried the latencys of the ram. would you think my raisingf it up would help. if you go on you tube and search "e6300 overclocked" exactly like that my video is the second one. it has a video near the end that shows cpu-z if that helps