boot.img unpack repack

I need a tool to unpack latest boot.img from 64bit
Software number: 1.51.401.4
Kernel version: 3.10.28-g930be6d
and@AABM #1
SMP PREEMPT

I need to remove system write protection.
Why? With this boot.img phone is more smoothest, If I flash an older boot.img is slower.

Sorry for my bad english :d