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I don't know that I'd classify car engine production as 'heavy manufacturing'

You need to smelt and cast iron/aluminum for engine blocks, which is energy intensive.

Pretty sure those don't run on electricity.

Energy isn't just electricity. Could be gas as well.

Electrical aluminum smelters are pretty common. They consume an insane amount of power, 13 to 15 MWh / ton! (to produce aluminum from raw ore).

For foundries the picture is a bit better, for instance:

There are also gas fired ones and various special purpose furnaces (recycling, for instance).