Actualy yess, I have seen it. There is a groove of carbon deposit at the top of the block cilinder. But it's there because the piston rings don't travel to the very edge of the block. Going 7000 rpm instead of 2000 will not bring the piston closer to the edge so is will not change anything.
I have found that picture online, it is not accurate since the rest of the block is just too clean but it represent where it is. Usualy the groove is smaller than that and form a powder when removed.