Originally Posted by lemmonhead

more layers is not necesarly better. thicker head gaskets could cause problems by adversely changing the geometry of the head-block interface on the intake manifold , this is on Vee-type engine though.
But for out inline engines it could also subtly alter cam timing. but worst of all it could degrade the squish effect in the combustion chamber which can be greater pro-knock factor!!
your best bet is to o-ring they cylinders by machining a shallow groove into the fire-ring area of the block or head around each cylinder bore then installing gapless machined-steel rings or steel wire into the groove.