Abstract: This invention is directed to multi polymer structures for internal combustion engines, as well as structures for other vehicle drive train parts. For example, a valve rocker cover for an internal combustion engine in accordance with this invention is a composite of at least two different molded thermoplastic resins, which structure comprises a valve cover body molded of a polybutylene terephthalate resin and a sealing flange molded of a polyetherimide resin, with both parts in a bonding relationship. The valve rocker cover can also have attached to the underside a sealent so as to provide a seal between the valve cover and engine block when so assembled. The method of producing a composite in accordance with this invention is either insert molding or coinjection molding.