No danger involved with overclocking it, assuming the voltages you use are safe.
To raise it, you'll need to increase the QPI/VTT voltages and possibly the DRAM voltage.
For benching with Westmere (your 980X), it's recommended to keep QPI/VTT around or below 1.55V QPI/VTT. DRAM can be anywhere within 0.5V of that, so up to 2.05V if your sticks are up to the task (I like to keep mine below 1.95V). Westmere is particularly picky about QPI/VTT voltages though. Sometimes it doesn't like to boot above 1.45V or so but it all depends on the chip. For benching with Nehalem (920, 930, etc.) it's usually recommended to keep QPI/VTT around or below 1.6V.
Realize these voltages aren't for those afraid of killing chips. While they most likely won't do any immediate damage, there is the possibility that you have a chip that will commit suicide as the voltages go up. Many people are scared to go above 1.65V on the memory but that was just a fear caused by the ES versions of the Core processors. There have been very few reported deaths since the early revisions and most of them involved a large difference (0.5V<) between the memory (DRAM) and uncore (QPI/VTT) voltages. The memory itself (DDR3) can handle up to about 2.2V-2.3V without dying, depending on the individual IC's. Many do not see a performance gain above ~1.9V or so without actively cooling them (subzero), so if you're pushing them for fun, quit when the sticks stop scaling.
For 24/7 on both Nehalem and Westmere, I prefer to keep my QPI/VTT under 1.4V and my DRAM under 1.72V. You will not kill anything at these voltages, but as a general disclaimer if you happen to do so, I gotta say it's not my fault! You are voiding warranties (overclocking at all is voiding warranties).