I polished a cast aluminium intake manifold for a V6 once.
Never again.
Took about 120hrs, but turned out to an even better finish than this one (not my pic, as I don't have my images on this PC, and external hosted images have expired):
https://www.aulro.com/afvb/images/im...2014/07/40.jpg
The job in the OP would have been massive. Especially with all those intake runners.
