Tech Corner: How-to use a carburetor on your LS Swap!

There are a lot of good reasons to consider using a carburetor for fueling when swapping to an LS engine. The engine itself doesn’t care whether it achieves it’s ideal fuel ratios through EFI or using a carburetor. Sometimes it’s a matter of familiarity, or the fact that the car already has a carburetor on it, saving an expensive fuel system upgrade.



Using an  LS engine with a carburetor isn't about stepping backward into the past; it’s about choosing a different path to performance. For many performance enthusiasts, it strips away the digital "black box" of EFI and replaces it with a tactile, mechanical experience many hot rodders prefer. Even better, the swap is easy and the list of required parts is low.

To swap a carburetor onto an LS engine, you primarily need to replace the fuel injection components with a dedicated intake manifold and an ignition controller, but there are other changes to take into consideration as well. Because LS engines lack a traditional distributor, the ignition controller is essential for managing the spark timing for the individual coils. We highly recommend the MSD 6014 and 60143 boxes for this purpose.

Essential Conversion Components

• LS Carbureted Intake Manifold: You must choose a manifold that matches your cylinder head port shape (typically cathedral port for most 4.8L, 5.3L, and 6.0L engines, or rectangular port for LS3/L92). We have several good alternatives, for every application from daily driver to full on race car.
  
  
• Ignition Controller: This "brain" connects to your factory crank and cam sensors to fire the coils. Modern units like the MSD LS Ignition Control Box are plug-and-play and work with both.
  24x and 58x reluctor wheels. We’ve got all the installation videos you need over on our Scram Speed Youtube Channel.
  
  Here's one. We cover the software and other aspects in other videos. Check it out! 
  https://youtu.be/Ap4i1CHSHO4
  
  
• Fuel Pressure Regulator: Carburetors require much lower pressure (5–7 psi) than EFI systems. If you are using an EFI fuel pump, you must use a bypass-style regulator to drop the pressure safely. We find that trying to do this in a single stage is not reliable with many aftermarket fuel pumps.
  
  
  
  We prefer this Aeromotive two stage regulator.
  
  You can also use a regular carburetor regulator between an adjustable EFI return style regulator and the carburetor.
  
  
• Throttle Cable Bracket: Since the factory LS throttle was often "drive-by-wire" or designed for a different intake, a specific bracket is needed to secure your classic throttle cable to the carburetor. We like this bracket for GM standard throttle cables. It fits standard 4150, 4160, and Carter-style Edelbrock carburetors. Does not fit Dominator or Edelbrock VRS carbs.
  
  
  
  
• Alternator control: Most LS style alternators required a 12V exciter wire. We carry an easy to install harness that you plug into a switched 12V source to ensure the alternator charges correctly.
  
  
  
• Fan Activation: In a factory application, the computer controls the fan activation on an LS engine, and the carbureted control systems like the MSD 6014 do not provide that functionality. For best results an aftermarket fan controller is required. We sell this controller for up to two fans which is easy to install, has labelled connections, a compact weatherproof fuse and relay box, and it plugs in to one of our thermal fan switches that are a direct bolt in for the LS engine. Installs quickly and looks great.
  
  
  
  
• Thermal Switch: If you have your own fan control, you can still use one of our LS direct fit thermal switches here for any controller that activates with a ground circuit. We carry them in 180, 190, and 200* activation.
  
  
  
  

We’ve helped a lot of people with these swaps and offer recommendations for which carburetor to use with just about any LS engine and application. We carry many options in stock. If you’re interested in getting a recommendation for your build, we’d be happy to help!



You can see most of the parts featured above here:
https://www.scramspeed.com/lsx-carburetor-swap/