What Car Part Would You Never Buy A Cheap Knock-Off Version Of?

Amazon is a grand marketplace where you can buy all kinds of car parts. You can find just about anything you’re looking for on there, and usually at a reasonable price, too. However, if you’re heading there to purchase a new carburetor of questionable make, be wary. You might not be getting the reliable bargain you hoped for.

Let’s start with an example. Uncle Tony’s Garage specializes in working on old-school muscle cars. In a new video on YouTube, Tony says he’s having trouble with a cheap knock-off carburetor. His solution? Tearing it down to figure out why it’s performing so much worse than an original example from sixty years ago.

The carb in question is an unofficial reproduction of a Carter BBD [Ed Note: I hate the Carter BBD. I replaced mien with a Motorcraft 2150.  -DT], a dual-barrel carb used on a variety of models. By pulling it apart, it becomes clear that this modern knock-off has some serious deficiencies compared to the genuine article.

They Don’t Make ‘Em Like They Used To

Tony’s not outright against knock-off carbs. “These cheap knock-off Amazon carburetors, I have used a few of them over the last few years, because in some cases, you can’t get a legit reproduction,” he explains. He notes that the price of the reproduction carbs is “dirt cheap” compared to sourcing an original example in good condition, and sometimes, it’s your only option. While he’s had some success fitting them in the past, he notes this is the first time he’s examined one that’s been in use for some time. He’s less than impressed with what he finds.

It all started with an old Barracuda project that wasn’t running quite properly. “So we bought this thing a month ago, drove it from where we bought it to the shop, and it needed work, you could tell that it wasn’t quite right,” says Tony. “No big deal, we’ll give it a tune up and we should be able to move on.” Yet despite fixing a number of obvious external issues on the engine, including swapping the intake out and a replacing a broken exhaust manifold, the car continued to run poorly.  “It would never idle the same way twice, it would surge oddly… it was weird,” he explains. “It had a very very weak accelerator pump, which is unusual because it’s a relatively new carburetor.” That carburetor in question was the knock-off version of a Carter BBD.

With the carby on the bench, the inspection begins. “You can see it’s still in relatively new shape, visually it looks like it just came out of the box; a little dirty on the front, but that’s your overall condition of it,” says Tony, noting that on the outside, it look relatively okay. But just by feel, he says you can tell it’s not the real deal. He compares it to a Carter BBD off a running car that’s sat on the shelf for the last ten years or so. “The very first thing you notice is how light [the knock-offs] are, they probably weigh two-thirds of what an original carburetor [does].”

But what of the internals? “Both of these carburetors have been used on 10% ethanol gas,” says Tony.  Despite the fuel’s poor reputation, the float bowl lid of the original Carter BBD looks fresh, clean and new. In contrast, the same area on the knock-off carb looks to be significantly corroded.

Uncle Tony puts both of these matters down to a difference in material quality, stating he believes the OEM parts were made with a superior alloy. Tony refers to the knock-off as being made of “plain aluminum” which probably isn’t the case.

It’s more likely the knock-off is using a crappy alloy rather than raw aluminum with no alloying elements at all. Indeed, many carburetors are made out of zinc alloys—and many carburetors on Amazon claim to be just that. Whether they’re made of specific alloys that are fit for purpose is another thing entirely. The corrosion would suggest they aren’t.

As for the accelerator pump? “I noticed [the knock-off] had a very weak accelerator pump shot, which is unusual, as BBDs have a very strong shot, generally speaking,” says Tony. The accelerator pump is crucial for drivability. It’s responsible for squirting an extra dose of fuel into the engine when you lean in to the accelerator—hence the name. Examining the accelerator pump on the knock-off carb reveals corroded parts with a hardened seal that would almost certainly be harming performance. Meanwhile, the older original Carter BBD has cleaner parts and a far fresher looking seal despite being a decade or more older.

It’s worth noting that these corrosion issues can seriously affect performance in a carburetor. Metering jets and moving components of the carburetor are very sensitive to dirt and debris. If they clog up and no longer flow or move freely, the carburetor will fail to meter the right amount of fuel, and the engine will run poorly. Having a carburetor that’s quickly corroding is a recipe for trouble, and it’s unlikely to run well for long.

As for the odd surging issue? Uncle Tony puts it down to the metering rod assembly. The metering rod  assembly moves in response to engine vacuum, and is responsible for leaning out the mixture at low engine speeds. While the rod on the original carb moves freely, on the knock-off carb, the moving plate sticks easily. It’s showing some corrosion, and appears to have not been clearenced properly to the guide rod. This would severely interfere with the ability of the carb to deliver the right amount of fuel.

“Do I fix it? Do I go through it and try and make it function correctly, or do I throw it in the garbage?” asks Tony. “It’s obviously junk, but I’m going to work with it anyway, because a lot of you guys are going to be faced with the same situation.” His plan is to replace the accelerator pump and fix the metering rods so they move up and down freely. He points out that since old genuine carburetors are getting so thin on the ground, sometimes your only option is to work with what new parts are available on the market.

Like I said, Tony’s experience of these types of carburetors hasn’t been universally terrible. “I’ve been optimistic about these carburetors, and my experience in taking them out of the box and then bolting them on something so far has been fantastic,” he says. “This is the first one of these carburetors that’s been through a few cycles, it’s been through a year or two under the hood, it’s had fuel sitting in it.” His ultimate finding? While these carburetors work well when they’re new, they don’t seem to have anywhere near the longevity of the genuine article.

The final assessment? “My opinion of these things has definitely gone down somewhat,” Tony says. He doesn’t recommend avoiding them entirely, noting the realities of the modern market for these parts. “If you can’t find an original, usable version of what you need, sometimes it’s your only alternative,” he says. “But I would say it’s a good temporary alternative—something that will get your car running and down the road long enough for you to find the right thing and swap it on.”

Again, we only just showed a single example, so maybe that Amazon carb isn’t as bad as it seemed. With that said…

Not An Isolated Example

Tony’s not the only one out there tangling with these knock-off carburetors. YouTube channel Muscle Car Solutions has done multiple reviews of cheap knock-off carburetors, and he’s often less than impressed. One of his most popular videos concerns a cheap Edelbrock-type carb that he purchased on eBay for $230.

From the drop, his opinion is altogether negative. “I have to apologize for having this hot pile of garbage on my workbench,” he says. “It was worth it to show you why you should not spend your money on a knock-off carburetor that clearly has no business going on anything.” His first complaint? The quality of the Phillips fasteners that hold it together, as opposed to the nicer Torx hardware in modern genuine Edelbrock carbs. “They use the absolute cheapest garbage they can find,” he says. This can make it difficult to work on the carburetor without stripping screws and the like.

Other problems he identifies include a weak step-up spring, a broken float, and cheap gaskets. There’s also no thread locker on important fasteners, which can put your engine at risk if a screw happens to come loose. Nor were there reference markings to line up the electric choke. Worst of all though? This particular carby had proved difficult to tune on idle. That turned out to be because one of the idle screws had broken off inside the carb and was no longer properly adjustable.

This carb had only run for 30 minutes on the dyno. There’s no evidence of corrosion or anything like that, unsurprising given its short period of use. Regardless, the disassembly shows a whole bunch of other problems that you can find with these cheaper knock-off parts. Between its weak springs and broken components, it wasn’t exactly predictable during tuning. “Erratic was the word that was used to describe how the [air fuel ratio] bounced around,” he says. “It’s just not gonna be able to give you the correct control over the fuel system.”

Head out to auto forums and you’ll find plenty of other people griping about their knock-off carb experiences. There are tales of clogs from metal filings left over from manufacturing, poor quality castings, and lots of problems with leaks. The general consensus from most is that while sometimes you’ll get a good one, the quality is hit and miss at best.

The graveyard of chinese carbs
byu/john4927 inJustrolledintotheshop

Not The Best Choice

There are some parts of your car where you can often get away with cheaper parts. An exhaust, for example, is pretty simple—it’s some metal tubing welded together with a flange or two. Similarly, things like radiators, gas caps, and bulbs are unlikely to give you much trouble unless they’re really badly made. But a carburetor? Not so much.

You can almost think of a carburetor as a complex mechanical computer. It measures airflow and responds by dosing the correct amount of fuel in response. It does this across a wide range of engine operating conditions, from idle to high RPM, from cruising to high load hill climbs and hard acceleration. To achieve this feat, it has a ton of tiny little parts that all have to dance together perfectly to get the fuel delivery just right. It’s a precision piece of equipment that needs to be built well to work properly.

If you build a carburetor in a slapdash fashion, you’re going to have all kinds of problems. If your idle screws are falling apart, you’re never going to get your engine to tick over nicely. If your accelerator pump leaks, the car’s always going to hesitate when you hit the gas. If everything’s corroded, parts aren’t going to move freely and your jets are probably going to end up clogged, leaving your engine running lean or maybe even stalling out.

It’s a simple fact that carburetors are too mechanically delicate to run well when you build them without proper regards to quality. You might get lucky with a knock-off that’s put together well and manages to hang together for a while. But the truth is that the genuine article is more expensive because that money is spent on proper parts, proper materials, and quality checks that ensure the thing actually functions the way its supposed to. You can cheap out on those things, but you’ll often suffer the consequences.

You might save yourself $500 to $800 on a cheap knock-off carb. But if it has problems, and it costs you a day or two of tuning time? Then it’s all a wash and you’re out just as much cash anyway. Sometimes it’s easier to save yourself the trouble.

Now, since this is Autopian Asks, I put it to you: what car part would you never buy a cheap knock-off version of?

Image credits: Uncle Tony’s Garage via YouTube screenshot, Amazon, eBay, Muscle Car Solutions via YouTube screenshot, Summit Racing