Turbo Compatible Carburetors

Although fuel injection (be it mechanical or electronic) is generally the best option for use with turbochargers and superchargers, there's no reason that a properly tuned carburetor can't offer comparable horsepower and driveability. Carburetor options and configurations abound; the devil is in the details of tuning everything to run well, both on and off boost.

Any Carburetor

  • There are two basic types of carburetor/turbo setups: blow-through and draw-through. Blow-through setups are so called because the carburetor is between the turbo and the intake, so the turbo "blows through" the carburetor. Draw-through setups put the turbo between the carburetor and engine, meaning that the turbo draws air and fuel through the carb. While draw-through setups do have their limitations, the carburetor doesn't know or care why the air is going through. All that matters is air volume and velocity, so any properly sized carburetor will work.

Modified Vacuum Secondary

  • Carburetors also come in two basic varieties: vacuum and mechanical secondary. Mechanical secondary (a.k.a. "double pumper") carbs use a hard throttle linkage and a mechanical linkage to shoot fuel into the engine. Vacuum secondary carbs use a hard mechanical linkage to operate the primary barrels, but use vacuum signal from the engine to open the second set. Modifying vacuum secondary carburetors to provide extra fuel under boost is a very involved process, and involves drilling and tapping into the carb body. If you don't feel comfortable doing this, you might want to consider an off-the-shelf carb modified in such a way. Remember, you'll also need to install a nitrophyl bowl float to prevent float collapse under boost.

Commercial Boost-Referenced Carbs

  • Several companies manufacture carburetors already modified to perform under boosted conditions. Some of these companies, like Barry Grant/Demon Carburetion and Edelbrock, manufacture their own blower-specific carburetors, while others, like Procharger, AED, Chuck Nuytten and The Carb Shop, specialize in modifying existing Holley, Quadrajet, Thermoquad, Stromberg, DCOE and Carter AFB carburetors for use with boost. Whether you choose an off-the-shelf unit from one of the big manufacturers or a modified unit from a carb tuner is a matter of personal preference, but many carb tuners will offer the option of custom tuning a fuel mixer to your specific application.