Seeing an O-Ringed Block is very common in the world of High Output engines with extreme operating pressures such as engines using high compression and or Blowers as well as NOs. This is necessity in order to avoid the pressures from pushing their way through the head gasket and into the coolant passages or crank case (doesnt that give you an idea?). There is a tool just for this purpose, cutting a ring around the cylinder inbetween the cylinder itself and the coolant passages. Tapped into the groove is a thin wire (18 guage galvanized safety wire is what I use). Sticking up about .010", the wire bites into the head gasket completly sealing the compression where it should be anyway..It puts up a wall basicly. This illiminates blown head gaskets. The use of solid copper head gaskets makes it impossible to blow through the gasket fibers due to the fact that there are no fibers. If the gases actually made it through the solid copper, it would get right about where that wire is and thats it..you would never even know. What I am talking about here is O-Ringing the cylinders on the 5.7 during any event that involves the engine being rebuilt. I am currently as of 5.31.00, assembling the long block on my 350 project. I will keep you posted on how it does when it comes to life.