Short answer: no you cannot. The sector size is set by the manufacturer of the drive. 512 bytes is pretty much a standard these days. However, if you mean can you change the block size (which is a multiple number of sectors), that can be done when you format a file system, such as ext2 or ext3. BUT, you certainly cannot set it to 520 bytes. As I said, the block size has to be a multiple number of sectors. IE, N x 512 bytes.

So, why do you want to do this?