Carburetor Tuning

So why should we care about a low-tech item that no one uses anymore? Well, one reason is that there are a lot of cars running today that still use this old technology. Most collectible and resto vehicles rely on a carburetor to deliver the proper amount of fuel into the engine. And since these cars are older, the carburetors likely have problems.

Old-School Performance
Another reason that a vehicle may use a carburetor is for performance gains. It is true that fuel injection systems are very precise and can be modified for power increases, but often the cost involved in these modifications can be high. For this reason, the performance carburetor is still a very popular option in the sports racing world. So most people restoring an older car, or making performance modifications, will want to know a few tips and tricks for this old-school component.


The example we chose is a 1972 Porsche 914. In factory form these vehicles come with a very efficient fuel injection system. There are many options for performance gains with this system, but most of these modifications are much more expensive than a good set of 40 millimeter Weber carburetors.


The Weber brand is one of the most adjustable carburetors available today but because of this, they are often the most mis-adjusted carburetors. Keep in mind that the information we're providing applies to almost all carburetors, not merely Webers.

Carb Functions
The basic function of a carburetor is fairly simple. Air drawn into the engine through the carburetor mixes with fuel. It is the carburetor's job to mix the fuel and air in the correct amounts. Too much fuel, and the car will be sluggish, smelly and use excess fuel. Not enough air will cause the engine to "ping" or detonate the fuel prematurely in the combustion chamber, possibly damaging the engine. The engine tuner must therefore find the fine line between too much and too little fuel. This line can be narrow and elusive if you dive into a carburetor without any knowledge of the internal workings.