FWIW, if you want the silver engine/piston areas to be really metallic in appearance, Testors makes the Metal Masters "buffing metallizer" paints, which can be buffed after application to shine like the various metals they are labelled for. I used to use these to build sci fi models and props, and they look very much more like metal than any other paint, once buffed up.
You do have to start with a very smooth surface, the more polished the better, so you'd need to resurface the parts before painting with it.
This should be their source page, but I can't see the page because of all the scripting it uses.
https://www.testors.com/product-catalog/testors-brands/model-master
A google shopping page
https://www.google.com/search?q=testors+Metal+Masters&num=100&newwindow=1&sa=X&source=univ&tbm=shop&tbo=u&ved=0ahUKEwi0h_ns1e7XAhUKerwKHTt_CIkQsxgIKg&biw=1019&bih=917
A google image page
https://www.google.com/search?q=testors+Metal+Masters&num=100&newwindow=1&sa=X&tbm=isch&tbo=u&source=univ&ved=0ahUKEwi0h_ns1e7XAhUKerwKHTt_CIkQsAQIcQ&biw=1019&bih=917
You do have to start with a very smooth surface, the more polished the better, so you'd need to resurface the parts before painting with it.
This should be their source page, but I can't see the page because of all the scripting it uses.
https://www.testors.com/product-catalog/testors-brands/model-master
A google shopping page
https://www.google.com/search?q=testors+Metal+Masters&num=100&newwindow=1&sa=X&source=univ&tbm=shop&tbo=u&ved=0ahUKEwi0h_ns1e7XAhUKerwKHTt_CIkQsxgIKg&biw=1019&bih=917
A google image page
https://www.google.com/search?q=testors+Metal+Masters&num=100&newwindow=1&sa=X&tbm=isch&tbo=u&source=univ&ved=0ahUKEwi0h_ns1e7XAhUKerwKHTt_CIkQsAQIcQ&biw=1019&bih=917