You can always adjust the timing regardless of running stock or overclocked. Lowest possible timings and voltage depends on the mobo and the ram, so telling you what to set them to might not work. Your best bet is to experiment a little.
I can tell you it's generally safe to go .5 over the voltage they are rated at as long as you keep them cool.
You haven't told us what the stock voltage is for the ram, how can we possible suggest anything until we know that a least. Try 6-6-6-18 and be prepare to know how to recover from a bad overclock, that's the price you pay for tweaking. If your system doesn't like the setting you'll just have to experiment to find the lowest stable timings like I said earlier. Also running 1T/1N is a bit of performance boost, but again your system may not like it. Experiment experiment experiment.
I have my ddr3 running 5-5-5-15 1T timings, but not all ram and mobo combo's will handle that.
voltage is 1.65v and i know how to recorver from bios and my mobo have bios recorvery i guess i should some experiment lol just dont wanna mess up everything just gathering all information before and im at 1T atm from ehat CPU-z tell me what is the 1N for......? im a bit noob but im learning quick lol
only tried 2 timing 6-8-6 24 like it should run some1 told me to set it at the same timing that my mobo should usually do it auto... and it run perfectly and tried 5-6-5 20 and could do anything ill stick with 6-8-6 24 im happy with it