from wiki:
the Cosworth engine
This engine, based upon the Cosworth BDA, tipped the scales at 168 lbs, half the weight of its metal counterpart. Plastic parts included the engine block, cam cover, air intake trumpets, intake valve stems, piston skirts and wrist pins, connecting rods, oil scraper piston rings, tappets, valve spring retainers and timing gears.
The plastic Cosworth engine was raced over two seasons. It was raced in a T616 HU04 and competed in the International Motor Sports Association's (IMSA) Camel GT Championship in the Camel Lights (Group C2) category in 1984 and 1985. The car's best finish was a third in class at the 1985 Road America 500
Plastic automotive engine - Wikipedia, the free encyclopedia