Mroso, Could be wrong, but the best reason for a copper base gasket which comes to mind is for turbo application where dropping compression ratio is desired. in this instance there are usually different thicknesses avail.and sometimes used in comination.in these situations, spray Copper coat is usually used. for stock motors, my preference is OE.dry. Fibre/carbon head gaskests have weeped since inception. issuring head and cyl surafaces are flat & true are a must of course, but in my experiance original failure is at oil passage orings allowing eventual deterioration at gasket. coat ing these areas w/ Indian Head shellac and allowing to dry before installation helps. luck G
