I ordered replacement gaskets for my engine and an aluminum head gasket was included. There was no gasket in the engine from the factory. This gasket is soft aluminum, about .012 thick. Is it used to lower compression, or to seal the head better and increase compression? I'll be running the engine on saturday with the new bearings installed, and the new head gasket. Is this gasket a stock item, or is it used only for high nitro fuels?

Thanks