Claiming made in USA doesn't really work that way. Typically these days it's a percentage of the final value of an item. If a $2 chinese casting gets turned into a $100 final product, then it's "made in usa from global materials" or some BS. But they can't make 51% of their parts domestically and suddenly claim all their products are made in USA - that's why their stamped parts like breathers are marked made in china.
The thing is, the penalties for claiming 'made in USA' aren't very stiff, and so many companies DO claim domestic when in fact they are not. In Edelbrock's case, it's not hard to see they have their own production facility and are running parts there every day. Edelbrock makes most of their money running their foundry and they make castings for many others too. They would be shooting themselves in the foot to make castings overseas. Besides, buying bulk castings overseas is a tough cash-flow position to maintain for an industry that sees highly seasonal demand. If anything, I would suspect they make some of their tooling overseas, but they have their own tool and die shop too, so I doubt that's the case for much of their own products. If for no other reason, foreign tooling is always a nightmare to un-screw. It's the route chosen by cheap-*** startups or small businesses who's credit line comes from a card. Some of their outside customers are likely those cheap startups or small shops though, so I'm sure they deal with some foreign made tooling one way or another.
Owning expensive capital equipment like an injection molding facility or a foundry means it makes sense to sell an in-house product to use up excess capacity as your outside customer demand naturally ebbs and flows. Every major production shop I've worked for has the go-to jobs that keep the place busy between the big paying jobs. The base-load of in-house product or go-to jobs is what keeps the value-added processes (machining, plating, screen printing, etc) busy enough to justify their existence and then those capabilities are used to serve outside customers and that's where a company's main profit flow comes from. This arrangement also often helps keep retail prices level as things like material and energy cost fluctuate over time (remember when prices would actually come back down some after a big spike? the good ol' days..).
