The 1981 AMC OHV 6 cylinder engine for passenger cars is the first to use glass and mineral reinforced nylon 66 for an engine rocker cover. The rocker cover design uses a novel attachment system and RTV silicone sealant. Vydyne® R-400G nylon resin was developed by Monsanto for this engine application.The paper will discuss the development program from both a material and a part performance viewpoint. Material performance will be reviewed including physical property data and specific “under-the-hood” test data. Part performance results ranging from dynamometer testing, test track and fleet testing to initial production start-up will be reviewed.