What is the purpose and what benefits does it give? Please post pics if possible.

 

O ringing the block , Placing or inserting a ring of copper around the top of the sleve of a block to make it seal better with the head gasget. I have heard both good and bad about this. Good it seels well for a forced inducation car. Bad it will eventualy cut through the head gasget. hope this helps.
chris

 

Thanks