A method of securing a composite plastic part to an engine with a bolt or a bolt and washer. The bolt has a head including teeth that are adapted to engage either the part or the washer. The bolt is tightened to cause the teeth to compress the surface of the part to resist rotation that may become loosened as a result of vibration of the engine. The part may be an intake manifold, a cam cover or an oil pan. Locking features, such as teeth, may be provided on the clamping surface of the bolt and on both surfaces of the washer. Alternatively, a knurled or serrated surface may be provided instead of the teeth.