The term is Electromigration
Excessive Vcore and temperatures will result in accelerated "Electromigration", which prematurely erodes the traces and junctions within the processor's layers and nano-circuits. This will in turn eventually result in Blue-Screen crashes, which will become increasingly frequent over time.
Short-term solution (not recommended): Increase Vcore to regain stability, which will further accelerate Electromigration and shorten the time interval to the reoccurrence of Blue-Screen crashes.
Interim solution: Decrease overclock to temporarily regain stability.
Long-term solution (recommended): Limit your overclock, Vcore and temperatures to stay within reasonable guidelines.
You might want to read the following Sticky: Intel Temperature Guide
1.4 Vcore is not
recommended. Unless you're into competitive overclocking on extreme cooling, most overclocking guides as well as many experts will insist that 1.3 Vcore is as high as a 22 nanometer processor should be pushed.
Vcore settings should not exceed the following:
45 Nanometer 1st Generation ..... 1.40 Vcore
32 Nanometer 2nd Generation .... 1.35 Vcore
22 Nanometer 3rd Generation ..... 1.30 Vcore
22 Nanometer 4th Generation ..... 1.30 Vcore
At 1.3 Vcore, whatever stable overclock a particular processor sample is capable of giving you is what you should consider to be it's limit. I know that's not the answer you want to hear, but that's the most appropriate answer I can give you.
Only the very best of samples will give you 4.8. I spent a huge amount of time testing 5 of these i7 4770K's before I found the one I'm running. The only way she'll give me 4.8 is if I turn off Hyperthreading, but I'm very pleased with it at 4.7.
has pointed out, when it comes to overclocking, not all processors are created equal; each one is unique.