If you’ve ever popped the hood of a Chevy Silverado or a Cadillac XT6 and stared at that massive hunk of metal making everything go, you’re looking at the handiwork of a very specific group of people in Michigan. Specifically, the folks at GM Saginaw Metal Casting Operations (SMCO).
Honestly, most people don’t think about where engine blocks come from. We just assume they exist. But the reality is a lot more "liquid fire and giant robots" than you’d expect.
Located at 1629 N. Washington Ave, this place has been a staple of Saginaw since 1919. That’s over a century of pouring molten metal into molds. It’s huge—nearly 2 million square feet. To put that in perspective, you could fit about 35 football fields inside and still have room for a lunchroom.
What do they actually make there?
You won't find them building entire cars at SMCO. Instead, they focus on the "bones" of the engine.
They specialize in aluminum engine blocks and cylinder heads. If you’re driving a GMC Acadia or a Chevrolet Colorado with a 3.6L V6, there’s a massive chance the heart of that machine started as a glowing orange soup in a Saginaw furnace.
They don't just stick to the V6, though. The plant has historically handled parts for the 5.3L and 6.2L V8 engines too. These are the heavy hitters. The ones that tow trailers and scream down highways. Once the castings are cooled and cleaned, they get shipped off to assembly plants like Tonawanda or Flint to be turned into a working propulsion system.
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The "Lost Foam" Magic
You've probably heard of sand casting. It’s the old-school way of doing things. But Saginaw is famous for something called Lost Foam Casting.
It’s kinda brilliant, actually.
- They make a replica of the engine part out of polystyrene (basically high-tech Styrofoam).
- They bury that foam shape in a big vat of sand.
- They pour molten aluminum directly onto the foam.
- The heat vaporizes the foam instantly, and the metal takes its place.
The result? You get a metal part that is incredibly detailed. It allows engineers to design complex internal passages for oil and coolant that would be impossible with traditional molds. It’s the difference between carving a statue out of a rock and using a 3D printer, but with 1,200-degree liquid metal.
Why Saginaw still matters in 2026
There was a lot of talk a few years back about internal combustion engines (ICE) going away forever. People thought foundries like this would just vanish.
Not quite.
Even as GM pushes toward an "all-electric future," the transition is messy. People still want trucks. People still need SUVs. As of 2026, GM has continued to lean on SMCO because the demand for high-efficiency gas engines hasn't evaporated. In fact, GM’s recent manufacturing strategy has been about "flexible" production. They are keeping their traditional engine plants humming while they build out the Ultium battery sites.
Basically, Saginaw is the insurance policy. It’s the reliable workhorse that funds the electric revolution.
Dealing with the "Grey Iron" Ghost
You can't talk about Saginaw casting without mentioning the history. For decades, the site was known for its "Grey Iron" foundry.
It was a tough place to work. Dirty, hot, and—as we eventually found out—dangerous. There's a long history of asbestos exposure and environmental issues tied to the old-school iron operations. A lot of the old malleable iron buildings have been torn down or remediated.
Today’s operation is a different beast. It’s cleaner, heavily automated, and focused on aluminum, which is lighter and better for fuel economy. But the legacy of the "Foundrymen" still defines the culture there. It’s a multi-generational thing. You’ll meet guys on the floor whose grandfathers were pouring iron for the original small-block V8s back in the 50s.
The Economic Reality
Employment numbers at the plant have fluctuated over the years, but it remains a pillar for UAW Local 668.
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When GM announces a $200 million or $500 million investment in Michigan manufacturing, places like Saginaw are usually on the list for "retooling." Retooling is just corporate-speak for "we need to change the machines to build a slightly different engine."
Without this plant, the Saginaw economy would look very different. It’s one of the few places left where you can get a high-paying manufacturing job that doesn't necessarily require a four-year degree but does require a massive amount of technical skill.
What to watch for next
If you're keeping an eye on the industry, watch for how SMCO adapts to "Giga-casting" trends. Some competitors are starting to cast entire chassis sections in one go. While Saginaw is an engine specialist, their expertise in aluminum casting makes them a candidate for whatever weird new shapes the cars of 2027 and 2028 might require.
Actionable Insights for Following SMCO:
- Check the VIN: If you own a GM vehicle with a V6 or V8, look at the engine code. If it’s a High Feature V6, parts of it almost certainly spent time in Saginaw.
- Monitor UAW Updates: Local 668 is the best source for "ground truth" on what’s actually happening on the floor versus what the corporate press releases say.
- Watch the V8 Lifecycle: As long as GM continues to produce the small-block V8 (which is currently slated to live well into the late 2020s), the Saginaw Metal Casting Operations will remain a critical hub in the global supply chain.