How Carburetors are Made (Basically Magic) - Holley Factory Tour | Smarter Every Day 261

20m read

·Nov 3, 2024

Hey, it's me, Destin. Welcome back to Smarter Every Day! In a previous episode of Smarter Every Day, I went to visit my dad and found him repairing a carburetor on his filler. After he told me how they worked, we went away and made this a transparent carburetor; you could actually run fuel through this thing. So Dad and I went to the garage. We used a high-speed camera to see through the carburetor, and we can actually see the fuel being atomized as it goes down into the engine.

[Music]

I highly encourage you to go watch that video if you haven't yet, but basically, we made the simplest carburetor possible. It has a bowl down here, it has a float, and it has a venturi. You can see the choke and the throttle here. This thing is technically a carburetor; however, a lot of people pointed out that it's not a real carburetor. There's so much more that goes on in a carburetor to make an engine work, which is why today we're going to look at an actual carburetor. This is a Holley carburetor.

We're going to open this thing up. Check this out; it's got a smell to it. It smells like gas. Alright, so let's open this thing. Let's just look at it for a second. Sometimes that's good; I can tell you this right now, there is way more going on with this bad boy than what we've got. We've got a venturi on ours, we've got four holes here; it looks like we even have venturis. Venturis! Yo dawg, heard you like venturis. Okay, a lot happening there.

Flip this thing over. Okay, so we got some floppy doos here, so let's turn. Okay, look at that! So when we turn this bad boy here, there's a linkage right here. Can you see that? Turn that thing, the linkage moves. Two-stage floppy-do action! That is serious. What else do we have? Oh, look at this! This thing goes all the way across, and there's a rocker arm here. Can you see that? When I operate the floppy dude, look at that; it's squishing something in there.

Okay, this is fascinating; there's a lot going on here. The other thing, though, I love manufacturing. My first two big-boy jobs were manufacturing jobs; cannot get enough of manufacturing. So here's what I want to do today; I want to take Dad, who taught me about how carburetors work, and I want to take him to the place where they made this. Because there's so much going on that we don't understand; like every little place you see a hole or a screw or machining, that obviously contributes to the operation of the motor vehicle. Otherwise, they wouldn't spend the money to do it. So this is fascinating.

Let's go to the plant where they made this. Let's take Dad! Let's make it a thing. Let's go on a road trip with my dad. Let's go up to the plant where they made this Holley carburetor. Let's find some smart people, and let's try to get smarter every day about carburetors.

Okay, so got Dad and Mr. Shane Weckerly. Are you over-engineering? Is that true?

No, I'm strategic planning and acquisition stuff.

Strategic planning and acquisition, but he knows all the engineering of this stuff. I haven't been talking in a while. What we're about to do is we're going to build a carburetor from the ground up, basically. Is that true?

That's correct.

Alright, and we're in Bowling Green, Kentucky. And, let's go. Let's go for it! So in your carburetor video, you had a lot of different channels and passages in your little mock-up carburetor, and that was actually one of the main pieces of negative feedback I got: "a carburetor is very complicated."

It is, but we simplified it.

You did, you did, and you did a great job of simplifying it! But this is really the brain of a carburetor. So this contains all of the various passages that basically tell the carburetor what it needs for fuel to mix properly with the air. So this would have your idle circuits in it, it would have your mid-range circuits, and it has your main circuits in it; it has your idle adjustment needles, and everything is in this one part.

So we take, and on our higher-end carburetors, they're made out of billet aluminum. So we take a solid block of aluminum, load it into this machine. This machine robotically loads it into a CNC mill, and it creates all of the passages and all the internal geometry that's contained within this.

Okay, so you said a few things; you said idle circuit. Yep, what else did you say?

So idle circuit, the mid-range circuit or transition circuit, and then the main jets, which is your wide-open throttle circuit.

Okay, and show me how I would control those.

You basically have fuel against this side, and then you've got a gasket on this side, and it creates passages here that the fuel mix with air and gets discharged into the engine.

Can I see it?

Sure! So it's these little channels here; they become passages once you put a gasket and pinch that between that and the main body of the carburetor. So I can imagine the size of that passage; the length of the passage in fluid dynamics, head loss, and stuff like that matters.

That's correct, so everything here is precisely engineered.

One of the things that people don't realize is a carburetor just doesn't inject fuel into the motor; it actually atomizes fuel within the channel. So you'll have a mix of air coming in here, you'll have a mix of fuel coming in here, and then it atomizes within this channel before it ever puts it into the motor.

So my video was a little bit misleading.

So where I had just fuel coming in, you're talking about there's some pre-atomization; which doesn't mean it turns it to atoms, right? It means it just turns it into small droplets.

That's correct.

Okay, cool. I'm with you.

Okay, so an idle circuit is when I turn the throttle down; that's the circuit that keeps it running, correct?

So when you're sitting there idling at a stoplight or wherever, that's the circuit that would be running at that time. When you start to accelerate, you've got to add additional fuel through a squirter and the mid-range circuit, and then that starts to transition in. Then, as you go to wide-open throttle, you would have a main circuit that would feed the wide-open throttle characteristics, and that's all we showed was the main jet.

Yes, correct.

So there's the idle circuit, the transition circuit, and the main jet?

Yep.

So we're making the brain of the circuit here?

Yep.

In here, you've got a robotic loader, and you can see it's got a bare aluminum block sitting there on one side of the pallet, and then it's got machined ones right next to it. The robot knows which ones it has pulled, which ones it has loaded, and which ones it's unloaded.

What's it called?

Panic.

I believe the way you pronounce it. Panic, that's a robot?

Yes, so basically instead of having a human hit cycle start, you're now having robots.

That's correct. So this machine runs unattended all day long. Somebody has to load new pallets in it, you know, maybe once a day or a couple of times a day, but other than that, it runs unattended.

So what you see here would be an unmachined casting; this one actually has had the first machining off here on the bottom, but it'll get some additional machining after this.

Okay, we also would have an unmachined base plate. I'm seeing all these ports and things like that; what's up with that?

Well, a lot of these speed vacuum passages, they'll feed vacuum to different parts of the carburetor; they'll feed different, like fuel out of transfer slots that'll be machined in later on.

So my understanding of a carburetor is it's a complex dynamic environment where even the size of a passage matters because it affects the flow rate?

Yes, everything matters, everything matters. So it's a balance, right?

That's correct. And so we're going to walk through this line; probably can't go into too much detail because it's a dark art, right?

It is, yeah!

But let's go for it. Let's build it.

Okay, sounds good. So the first stop is where the castings of the base plates are being machined down. Machining is when you use hardened tooling to remove excess metal from a part.

What plates they're machining here depends on what type of carburetors they're making on any particular day. They fly-cut the metal castings down to a certain thickness, and then they drill very specific size holes in them.

So the part gets loaded here. There's two tables to load parts; come over here, there's a check position here, then you go into here, and then you go into here, right? They do the same thing, so you have slower operations, and then you've got the one finishing up; that's the finished part.

Thank you very much!

So we've got two things going; we've got the base plate and the main body, correct?

The main body goes through a similar type of machining operation, machining the boards, the passages, the venturis.

So that bore has been machined?

Correct, that's amazing!

So you get pretty close on your casting?

We do, okay? We don't have to take a lot of material out of it. This is an example of a fully machined main body, so you can see it's been machined on the inside.

This one just touched the inside here; it doesn't machine the whole primaries, as you can see; you've got a lot of different passages and holes, a lot more than your carburetor you built made.

Why is this housing up here like this?

This is where a choke flap would sit, so this is where your choke seals off, and then it opens up once the engine's warmed up.

Four barrels? Yep, the choke is only on two of them.

That's correct because all of your slow-speed driving is only on the first two barrels. The other two come in when you go to more wide-open throttle.

Got it! That makes sense; does that make sense to you?

Absolutely.

So I'm going to take you to the start of the assembly line?

Yeah, sounds good.

I chase squirrels, and there's too many operations at this plant for me to be trusted to be able to ask whatever question I want. There's a lot of stuff going on.

There is main body assembly.

Okay, these are shinier.

These are shinier; these have been through the tumbler.

Okay, so we make carburetors in a lot of different ways; we make them shiny, we make them a gold dichromate, we make black ones, just depends on the finish the consumer's looking for.

So this one is ready to go down the main assembly line here; first operation is it will go in, have some air bleeds put into it, and then it'll start down the line having various components bolted onto it as it works its way down the assembly line.

So that's installation of the squirter nozzle. These are two-barrel carburetors being built here; these are two barrels being built.

Girls, instead of a four-barrel!

She installed the what nozzle?

The squirter nozzle!

So we talked about that transition circuit. The transition circuit is when you need to put in additional fuel to get to, you know, your intermediate. When I hit the gas pedal, unlike mine, you can't wait on a main jet; you have to have something ready.

You've got to have something to squirt in additional fuel. So she installed the squirter that has two squirter nozzles that spray out.

And what's happening in this operation?

So this operation here, she's actually putting in what's called the booster.

So I'll reach over her here. Where you had the tube that stuck up in your carburetor, this actually is what we call the booster, and are it's your tube, but it's this way, and then the fuel comes out the bottom.

So she is staking these into the main body so they can't fall out.

Gotcha! And so from here she does what?

So she's putting in these little—they're called air bleeds. Basically, they are like a jet, but they meter air instead of fuel.

When I talked about the air and the fuel having to mix together to emulsify, that air gets metered through that, so we control how much air goes in and how much fuel goes in and how they mix.

So it's a very specific hole!

Yes, we're starting to create precise orifices.

Correct, all of these drilled holes aren't good enough; you really need machined orifices.

Why are they brass? Why are most of the parts that go in brass?

A lot of it is because the brass doesn't corrode, and it can be broached very accurately.

So what's happening here?

She's installing a choke housing, so this is the part that contains a little spring that actually activates the choke open and closed depending on the temperature.

When the vehicle is cold, it needs richer air-fuel mixtures than when it's warmed up. The choke, when it's cold, closes and lets less air in, which forces more fuel into the engine. That little spring in that housing, as it warms up, has electric current pass through it.

As it warms up, it automatically opens the chokes and allows more air into the engine to normalize the air-fuel ratio.

On the one we made?

Yep, we had a choke; it was a flat.

Yup, your flap can think on its own!

Correct!

That's what we're doing; there's more than we can talk about here; you are witnessing the birth of a carburetor.

When this number is etched in, it's like naming a new baby—only a carburetor.

While this assembly line is running the main body of a two-barrel carburetor, another line is working on the throttle assembly.

I was only able to get footage of them installing the flaps for a four-barrel carburetor, but you get the idea.

My favorite part of this whole process is when they use threaded fasteners to position the flaps in place, and then they mechanically deform the screws so they can't be removed.

They're squishing it! It's almost like they're using machine screws like rivets! The sub-assemblies from both of these two assembly lines will eventually merge, creating the entire carburetor.

Alright, so what's going on here?

Okay, so you're getting down to a point now where the fuel bowls are starting to come in.

Okay, so we've done the venturi; we started doing the choke stuff.

Yep, next thing is the metering block and the fuel bowl, which will go onto this assembly.

Okay, so this piece here goes in.

Okay, look at that! That's very complicated.

It has two jets, a power valve, and a baffle.

Got its gaskets! Wow, that's amazing!

And you can see here some of the detail of the passages, the brass restrictors; that's a little bit different than what we did.

That's better than your carburetor?

Yeah, so this assembly will get mated to this one to create a main body and fuel bowl assembly.

So I have venturi here?

Yep! I got the body here?

Yep! I got the bowl here?

Correct! And I have a brain here, which I didn't have?

Correct!

Okay, you basically used a tube and an adjustment needle to create the brain.

Okay, got it, understood.

Interesting!

Okay, so how much engineering effort and human lifespan does this represent? Like we learned all this the hard way, right?

Yeah, I mean, carburetors have been around since the turn of the century, but they have evolved immensely over the years. Racing engines have changed; they've gotten bigger, higher performance. You know, you want tighter air-fuel ratios, so the carburetor is a never-ending evolution even today.

That's amazing!

Okay, gotcha!

So you're thinking very hard about where to put this back?

Yeah! I want to make sure I don't screw him up!

So I'm going to give you that back.

Got it!

Okay, so that was the bowl.

I didn't see a float; is there a float already in there?

I can show you that here; he knew exactly what I was looking for. He's on it.

This isn't his first tour; you've done this quite a bit, huh?

Alright, so this is a fuel bowl assembly; it has a sight window in the side and the fuel level in the fuel bowl just like your visible carburetor actually shows on the side of this.

This is the float assembly; this is where the fuel comes in through this fitting up in through this passage, so you can actually see if the float is stuck, correct?

Is that what's hot glass?

That's wonderful; that's great!

Did you ever have those on?

Not me!

Yeah, so the float moves up and down with the fuel level and when it reaches the proper fuel level, it will seal off and not let any more fuel come in.

Where's the needle?

The needle is back in behind here, underneath this nut and screw.

Can you adjust the needle here?

Yes, you can!

So this particular one of the benefits of a Holley carburetor is you can adjust the float level externally.

Externally? That's hard to do!

Yep, that's hard to do, and you can see it in the window just like your visible carburetor!

Well, yeah, that's amazing!

Well, are you adjusting the float level, or are you adjusting the relationship between the needle and the float?

You're really adjusting the needle; the relationship between the needle and the float, which as a result adjusts the fuel level.

Okay, that makes sense!

Now one other thing I'll show you—on this we talked about the intermediate circuit and the transition circuit, right?

This is a little diaphragm in here; that's called an accelerator pump. When you step down on that throttle, it pushes down on this lever.

Show me one more time please.

When you push down on this lever, it actuates a little diaphragm in here, and it squirts the fuel through the squirter that we saw being installed earlier.

Like a water gun?

Like a water gun, really!

Yep, so there's a mechanical pressure, correct?

Okay, got it!

Can I just pause and look at how beautiful it is?

That this is—can I see that?

So all those screws are torqued automatically.

So this is coming along here, so she's feeding parts this way, he's feeding parts this way?

That's correct!

So she's—there are separate lines that are feeding him and these other assembly lines down through here, so he's a critical point.

He is?

Okay, you're smirking; what are you smirking about?

He's good!

Is this you were producing this part and you're transitioning to this?

Correct!

So they've been making, you know, these carburetors all morning long; now they're transitioning to two barrels.

Line never stops; it just transitions into the next queue.

How long have you been here now, Benji?

Fifteen years.

Fifteen years? That's awesome!

You like working here?

Good place; I love it!

Been here at 52?

Your dad over there?

52!

Your dad's been here 52; you've been here 15!

What do you drive, Benji?

A 2007 Trailblazer.

Yeah, is it stock?

He just—he's not even going to get into it!

No, no!

What are you doing right now?

I'm putting on the starter body.

Body? Gas throttle body?

Throttle body? Gas?

What are you waiting on? You waiting on that part?

So you're ahead of production right now; that's where you want to be?

Yeah!

Okay, so as soon as it gets to you, you're gonna execute; you're gonna be looking at the next thing.

What are you doing there?

Setting the pump.

So you—you had it, you moved it until it closed, and then you set—you bent all those tabs till they touch?

Yeah, that's awesome!

So he's grabbing it up here; what'd you say?

Is that the automatic choke?

He said yes; putting the choke mechanism on.

So I talked—I talked about that thermostatic spring, there it is! That's a bi-metallic strip. It's a bi-metallic strip you put, you know, power and ground into, and then it heats this spring depending on the ambient temperature outside and how long the key has been on; it will change the choke block.

Did you just tell me there's a heated bi-metallic strip?

You're electrically heating the bi-metallic?

Yeah!

Yeah, yeah! This is too much!

This is a vintage muscle car carb, so this is probably either—this is probably a 3-2 for a big block Chevy, if it was 454—or 427.

Okay, yeah! So this would be like a '65 Corvette carburetor we produced these when they were new, and we still produce them today!

That's amazing!

How long has Holley been here?

Since 1952!

Wow!

So these are packaged, ready to go.

Yeah, but there's one more step I gotta show you.

Okay, how y'all doing?

Good morning!

So the carburetors come down the main assembly line; the last step before they go in the box is a quality check. One of the things that differentiates Holley from everybody else is we actually wet flow test every single carburetor with gasoline with mineral spirits.

Okay, so it has the same specific gravity without all the flammability concerns, but every carburetor actually is run, is filled with fuel with mineral spirits, run through the process flow test 100% to ensure that all the settings pass.

Wow!

So Monita is testing the carburetors as they come off the line. There's a machine behind me that I'm not allowed to show you, but I can blur it!

Yes?

Okay, so it's a machine where they actually test every carburetor, correct?

Yes!

So what are you doing?

Well, right now, I preset the other needle. I press, yeah, I preset idle needle, and I know how much I supposed to open, you know?

You know exactly how much to adjust it?

Yes, I mean, close enough!

Yeah, almost, so you open it, then close it, yes?

Okay, I closed all the way, all the way down; then I opened right now three-quarters; then I closed all the way down; then I opened like three-quarters, and now I'm gonna try testing.

Okay, here's the blurry part; I'm enjoying it!

You don't get to see it, and now I have to finish this one first, so this one's finished?

Yeah, this—the fast test!

And then now I have preset that fast idle?

Yes, that's what's called fast idle.

So you got—you got your data, and then you're making an adjustment?

Yes, adjustment like for gauge—the plate; look it, it has to be 29 on this model.

Yeah, you have to add a little bit more; it's like smooth and easy; I have to gauge.

So briefly, explain what a go-no-go gauge is.

A go-no-go, make sure you're not undersized and you're not oversized. If the go gauge goes in there, you're large enough, but if the no-go gauge goes in there, you're too large, and that's what you're doing?

Yeah, that's what I'm doing!

Okay, and after that, I make sure I drain fuel.

Like draining all the way?

Uh-huh, I'm just to look at my face for a minute!

Basically, she's draining the fuel off the device!

Okay, she—that was a good one!

So this is not tested; this is testing, this is already okay!

So here we go, check this out, I can describe what I'm seeing; there's a lot of—now I'm testing computer, working and waiting for wide open, yeah.

When wide open fast, now I can—oh wow, I see!

So she's testing different flow rates in different ways; we're making sure we're getting different pressures.

Okay, if I understand correctly, you're literally running liquid through it and running fuel through it, and you're testing the pressures, and you're getting real-time feedback on how it's doing, correct?

And we're growing a vacuum on it, right?

So it's simulating an engine running!

That's cool! How long have you been able to do that?

As far as I know, since the '50s when this facility was set up.

Pretty rad!

Last step, how are you today?

How are you doing?

Good!

Yeah, doing good, busy?

That's good!

So this is foam, right?

You gotta get the box closed before it blows up!

Alright, I don't know if you caught that; I want to show that again, that was really, really cool!

This machine has a bag in it, and it's got chemicals. I don't know where they are; there's chemicals either in the bag or something like that, and when he brings it out, it mixes those chemicals together, and it's like that spray foam insulation.

And it stays in the bag, and he throws it in the box, and it forms around the part!

Let's watch him do it one more time; that was pretty cool!

So he's putting that in there, so that's putting the foam in and squishing it, and then it starts growing, right?

It's like baking bread; that's growing really fast!

Thank you!

Thank you for your time!

If you don't put it underneath that roller, it will blow the box out and pop the top up!

Oh, so that's literally holding it together?

It is! So this right here is holding the box together?

Yep!

So when you open the box, it's custom-formed?

Right!

That's so [Music].

Top of the box too; you can feel some heat in them.

Oh, it's warm?

Yeah, it's an exothermic reaction!

It is, surely you haven't always done that; that's like a—

That's like a finishing touch kind of thing.

They've done that for the 20 years that I've been here. Before that, they used various cardboard and other structures in there to hold it in place; that's the quickest and cheapest way to do it. That's the best way; it's the safest for the product!

So you do this all day, every day?

That's a lot of carburetors!

Dude, I don't usually do this; I'm helping him out!

So where is he going?

So he's going to basically the back dock; he will load it on a truck at that point, and it will go over to our distribution center, which is about three or four miles away.

That's a lot of carburetors, dude!

It's a lot of carburetors!

So people are still putting carburetors on cars every single day?

Why?

In all honesty, they're a very simple device; people know how to work on them, they know what to do with them, they're comfortable with them, they're affordable and people like them!

Yeah, because they feel like a muscle car!

They don't—yes exactly!

And you know you can fix them anywhere, you know, side of the road; something happens, you can get parts readily available, and you can make it go again!

I love manufacturing!

Now that you know how carburetors are made, check this out! You remember the metering block between the bowl and the throttle body?

Here, well I didn't know this, but it actually gets input from way over here on the base plate!

There's a little slot down here; this blew my mind!

And as you operate the throttle here, look at that; that little slot opens up gradually, and the size of that slot precisely controls the airflow that's going to the metering block.

That changes between all the different circuits!

It's like a precise dance between pneumatics and fluid dynamics!

It's an analog computer; this is incredible!

And that is just another reason why I think carburetors are amazing!

What—you've got something in your ear, or you should have something in your ear.

I'm just joking!

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That's two magic tricks in a row! Let me show you what these things are!

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Oh, what is this?

We even got some lanyard action!

Oh, look at that!

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Let me do a little, uh, little—yeah!

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How Carburetors are Made (Basically Magic) - Holley Factory Tour | Smarter Every Day 261

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