Continental has introduced a new silicone rocker cover gasket, P/N 668893, and has been placed into several production engines. This part supersedes gasket P/N 658735. It is sure to provide a more flexible seal when properly installed.
668893 is a flexible, silicone gasket, smooth on both sides; with no special mating instructions.
See Continental SIL21-04B for further insutrctions. Dont' forget to add Loctite, P/N 658517, across the rocker cover screw threads per manufacturer insturctions.