I think it's pretty hard to make an engine in the 8 card kingdom - wharf+bank BM is very strong, and that combo allows you to safely wait to green if you see your opponent isn't going to contest provinces. In that case, the BM player can expect to double province at least once.
Engine problems: the only source of +action is nobles, which is terrible for that (necropolis for $6), and Golem (which might hit a lab if you're lucky or spend a long time getting a high lab density). With Fairgrounds at 6, it's possible, but that means you need a lot of terminal actions (with poor +action) among which Graverobber is a mostly dead $5 (note that you don't need a curse if you've got a potion). If you'd go for an engine in the 8 card kingdom, i'd like to hear how you think you can make it work. It may be that if you can hit 6 reliably and pick up a Nobles and a lab your golems would actually work.
On the other hand, if you through a cheap non-terminal or two in there, then the Golem can actually work for +action, the Haggler gets way better (now useful for more than silver when you don't hit 6), and the Graverobber can trash those for Fairgrounds later on (not terribly useful, but at least it's no longer dead).