The Performance requirement from Head Gasket.
As the cylinder block and head are not rigid body, when the Head Bolts are tightened, the gap between the surfaces and the surface pressure applied is not even across the whole surface. Moreover, due to combustion pressure and vibration while driving, the conditions are continually changing and the contact surface is being continually beaten. As a result, a good gasket must ensure that contact surface pressure is spread as evenly as possible and also adapt quickly to the ever changing gaps that can appear in the contact surface to maintain a good seal with good pressure.
STOPPER TYPE HEAD GASKET
A high pressure seal is formed around the combustion chamber through the use of stoppers which create a step within the gasket for optimum sealing. By making the stopper part of the plate also allows the fold to be smaller while maintaining structural integrity. One side of the plate is completely flat meaning that it can be layered with the stopper to allow stoppers to be used in even the tightest of locations around the combustion chamber forming a high quality seal. Compared with other gaskets of the same thickness, there are more layers in these gaskets giving flexibility which allows the gasket to maintain a good seal even when the engine tries to vibrate and move.
(Image for Illustration purposes only)