By now many have heard of the issue of accelerated wear in the valvetrain of the M156 engine. The materials design of the valvetrain components results in repeated contact of soft metals with hard metals. Eventually this can result in premature wear of the valvetrain, degrading engine performance or even causing engine failure.
Many M156 valve buckets are prone to "bleed down" resulting in excessive valve lash during cold start up, commonly heard as a loud tapping noise until the engine fully reaches operating temperature. Excessive valve lash is a major contributor to accelerated valvetrain wear. The M159 engine, used in the SLS and SLS roadster, features valve buckets that are of an improved design. The M159 valve buckets feature an anti friction coating to reduce wear on the camshaft lobes. They also have an improved hydraulic system that will not "bleed down" like the M156 valve buckets. Installation of M159 valve buckets will help prevent any premature wear to your engine's valvetrain and make for a quieter engine on cold starts.