NRW Design S65 Aluminum Valve Cover Set - BMW E9X M3

The factory S65 valve covers are made from a Magnesium Alloy.  While very light, Mg is known to become microporous.  Over time gasses leak though the Mg material and form “pimples” on the valve cover surface.  As it worsens, these pimples start to corrode the material underneath the factory coating.  This continued cycle over time accelerates the oxidation of the covers leading them to fail and leak oil through the corroded areas of the vale cover.  Mainly between the gasket channels.  The Mg valve cover is notorious for leaking around the edge due to oxidation and corrosion to the material having contact with air and water vapor which can not be fixed with a simple gasket replacement.

NRW Design valve covers are die casted from A383 alloy. This material was chosen by NRW as it is a far superior aluminum alloy to others, due to its properties for this application. Not all casts are the same and material choice is the big deciding factor for longevity and stability of a product. Other companies claim their cast products have seen a 10x fold return due to issues using cast. Yet their metal choice (6061) is the main reason for their issues.  The buying public hears the term 6061 aerospace grade and thinks it’s the far superior metal.  But 6061 is an extruded metal not recommended for all casting purposes.  The downfall is when making 6061 a molten metal and cooling it to a solid, it does not allow for grain structure formation, making it less suitable for casting.  Creating issues down the road such as cracks and weak metal that will fatigue much quicker.