Q&A / Tech

Mailbag: Choosing the Right Carburetor for Supercharged Applications

 

Q: I plan on installing a supercharger in the near future and I’m not sure what carburetor to use. Do I need to upgrade from my current carburetor to a larger carb to get the most from the blower? Are there any special tuning measures I need to take?

A:  Much depends on the intended use of your vehicle. If your blown engine is primarily driven on the street at moderate engine speeds (under 4,000 rpm) with moderate boost (4 to 6 psi), you won’t need a larger carburetor(s). However, at full throttle a blown engine can require 50 percent more air than an unblown engine. A larger carburetor(s) will be required to make full power.

Typically the carburetors(s) will need to be enriched by 5 to 10 percent on the primaries, and 10 to 20 percent on the secondaries. The idle mixture screws may need to be enriched by one or two turns. In either case, the carburetors need to be jetted properly to prevent a lean condition. A lean condition can lead to overheating and detonation. For initial start-up, it is better to have a slightly rich condition to help prevent the engine from overheating. After initial start-up, check the spark plugs for proper reading (color) and adjust the carburetor(s) accordingly. You want to see a medium to dark tan color.

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