Aftermarket car upgrades have always been considered risky, as one slight misstep might mess up the entire design and internal system.
The same applies to swapping TBI to carb: beginners must tread with extreme caution to ensure the car still runs properly after these changes.
My team would love to delve further into this matter to lift beginners’ confusion. Keep scrolling for more.
What Are TBI and Carb?
What Is TBI?
TBIs (short for Throttle Body Injections) deliver fuel to your performance engine by pumping it straight into the car’s throttle body.
This body is located near the intake manifold with one single injector, controlled by the ECU to regulate fuel based on oxygen reading, engine speed, and throttle position.
What Is A Carburetor?
Meanwhile, carburetors (or carbs) are mechanical devices that blend solid fuel and air to manifest the required combustible mixture for your engine’s operation.
Specifically, it creates low-pressure spots to pull fuel/power from the fuel bowl.
Once the engines suck in air through the venturi, this low-pressure design will draw the bowl fuel via a jet network to mix it with these new airflows.
The entire mixture is then transported to the cylinders.
How Do They Differ?
As can be seen, their fuel delivery systems clearly differ. TBI injects fuel via electronic control, while carburetors mechanically mix air and fuel to deliver the mixture to your engine.
While TBI is more efficient and has greater emissions control, their exorbitant prices, complex setups, and follow-up issues after cleaning have discouraged many drivers.
Carburetors, with their simple design and low cost, remain the trend for various car models; I am not surprised people want to switch their current TBI to carb instead.
Swapping TBI to Carb: What Are The Most Important Parts?
While swapping TBI to carburetor, you must install/replace these compartments accordingly: the intake manifold, distributor, fuel regulators/ electric fuel pumps, transmission system, air filter/cleaner, and, of course, the carburetor itself.
Intake manifolds on a TBI car distribute fresh outside air to the cylinders in your engine.
When paired with carburetors, their purpose slightly alters: the outside air will be transferred to the carb instead for further optimization.
Hence, the intake manifold connections must also undergo corresponding changes to guarantee a smooth TBI-carburetor swap. I suggest finding a high-quality adapter to adjust it properly.
Switching to a carb requires the need to change your distributors, too.
And that’s to be expected: your current distributor is being run by the computer, so pulling out the TBI will, of course, remove that computer as well.
The best distributor alternative for these cases would be HEI (short for High Energy Ignition), which fosters more powerful sparks and better usage of the wider gaps between spark plugs.
As such, the combustion becomes more powerful and complete, terrific for upgraded engine performance.
Adjustable Fuel Regulators
The TBI transmits fuel at a much greater pressure than a carb’s demands, so the old regulators are not exactly compatible with these new upgrades.
You might want to consider installing adjustable fuel regulators to your fuel line.
If you are not really a fan of adjustable fuel regulators, then fuel pumps are another option.
They are simpler, for once – and chances are your current fuel pumps have already been aging, anyway. Replacements will only be a matter of time.
Your current TBI transmission system uses modern sensors to inform the vehicle when it should shift. Now that you have decided to use carbs instead, there are two possible solutions:
- Buy transmission controller computers (from a dealership or online is fine).
- Install an entirely different transmission, which does not use electronics. For this option, a kick-down cable may also be required.
Air Filter or Cleaner
An air filter/cleaner is not really necessary in every case, but still highly recommended.
As the intake manifolds are sending air to the carb at higher pressure, there should be some protective filters to prevent debris from clogging inside.
They are the most obvious, so I decided to save them for last.
Do not just install a random carburetor; you must do proper research to decide which setup and durability will work best – even though the options do not seem that much different at first glance.
Other contributing factors (warranty, capability, etc.) also play a huge role.
Swapping TBI to Carb: How To Do So?
Note that the process of converting TBI to carb is quite complex and clearly not meant for beginners.
Unless you have some expertise or are an average mechanic yourself, it would be better to seek professional support.
Step One. Gather The Right Equipment and Tools
Before starting, prepare all necessary equipment:
- A TBI to carb conversion kit
- The carburetors themselves (which you have researched beforehand)
- Intake manifolds
- Adjustable fuel pressure regulators
- Stock fuel lines.
Also, to play on the safe side, keep a vehicle manual with you in case mishaps happen.
Step Two. Remove Your TBI System
Disconnect all the TBI’s electrical connections and batteries. Once done, remove the fuel lines, throttle linkage, and air cleaner.
Next, pull out the gasket and bolts to completely detach the TBI from its intake manifold.
Step Three. Install Your New Carb Intake Manifold
Bolt your new carb intake manifold to the car’s engine block. Make sure the gasket seating is correct and well-aligned with the manifold port.
Step Four. Install The Carb
Now install your carb onto the new intake manifold; while at it, double-check whether the major mounting bolts have been properly tightened.
Attach the throttle linkage and fuel lines to the carb, then settle the air filter/cleaner.
Step Five. Install Fuel Pressure Regulators
Put the pressure regulators between the carburetor and the fuel pumps. Adjust the pressure to the carb’s recommended setting (refer to its instructions/manuals for more info).
Step Six. Adjust The Carb’s Ignition Timing
Again, use the manuals or instructions to adjust the carb’s ignition timing. To ensure it is set up correctly, use timing lights.
Step Seven. Adjust Your Carburetor
Inspect and change the carb settings to guarantee the correct air fuel ratio. You may start and run the engine for 4-5 minutes first, then change the mixture screws and idle speed if needed.
Step Eight. Test/Fine-Tune Your New System
Get in the car and test-drive. Are there any lingering issues like fuel delivery error codes, ignition timing problems, or poor drivability?
If yes, fine-tune your car again until it runs smoothly.
Step Nine. Enjoy Your Carbureted Engine
Now that the swapping is finished and your system has been correctly tuned, you only need to sit back and enjoy the engine’s performance, torque, and throttle response.
Does The Swap From TBI to Carb Affect Power and Performance?
TBI uses higher technology than carburetors (which I already mentioned), so do not be surprised if there are slight decreases in power and performance.
- Power: TBI relies on electronic controls, resulting in more precise power delivery and fuel atomization.
Carbs, on the other hand, work on mechanical mechanisms, which are not always 100% accurate.
- Performance: The precise fuel meter above offers tons of other benefits, too, including improved drivability and throttle response.
Meanwhile, carburetor cars might experience slight response delays.
Still, remember that this sentiment does not always apply to every swap; there are hundreds of carburetor types and models.
Plus, you can always give the carbs extra tuning (with the help of an TBI to carb swap kit) to optimize their ignition timing, fuel-air mixture, and other relevant parameters.
If done right, they can offer comparable or even better transmission/ fuel delivery than their TBI counterparts.
Can You Swap From An EFI To A Carburetor?
Yes, you can.
First, remove the vacuum lines, harness, factory ECU, etc., then install your new carburetor or manifold.
Since EFI (electronic fuel injection) distributors are quite incompatible with the new carbs, consider replacing them with a D.U.I version.
You might also need new fuel delivery systems (either installing low-pressure pumps or purchasing pressure regulators is a good choice).
Do Carbureted Cars Smell?
Yes. Occasionally, they will give off a gas-like odor. That is because carb engines often arrive with float bowls to contain residual fuels after the car has been shut off.
On another note, mildew smell is also another potential culprit.
Do Carburetors Overheat or Rust?
Yes. Rusting/overheating is among the most popular issues with carbureted engines and cars. Hence, you should check on them frequently, at least every two-three months.
Swapping TBI to carb is possible, but quite complex.
Although my article does offer a detailed DIY guide for TBI to carb swap, I do not recommend you perform this task on your own.
Seeking help from an expert – or at least from someone you know with decent experience in the matter – would be great.