Whats in your system?
The thing is they gave you only a single 6pin for a reason. By using adapters you are trying to do something they didn't want you to do. If they wanted you to have an 8 and a 6 they would have done it. I see on newegg there are two different models of the CX430 now. (??? Thanks Corsair...) One has 28A on the 12V rail while the other has 32A. 336W vs 384. The GTX760 is rated around 175W I think, and probably depends on the model/OC. If you have an FX 125W CPU then that right there is 300W. If you have the first PSU this leaves nearly nothing for the rest of the system. If you have the second PSU and not much of anything else then you'd probably be ok. You'd be putting a lot of stress on a budget PSU which isn't a good idea. I'd say don't do if you have the 28A model, but safe to use the adapter if you have the 32A model. BUT if you use that 32A model I'd replace with something better ASAP. Don't use it till the PSU fails.