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The huge number of carburettors available on the market may seem confusing at first, but choosing the right one doesn't have to be difficult.

The first thing you need to ask yourself is the application that this carburettor will be used for - on a race vehicle, or street-legal. If you need a street-legal carburettor, give us a call with your make and model of car, or look up your vehicle in one of the listings.

You may have to choose between square flange and spread flange, choosing the type that was not made for your manifold will mean buying an adaptor.

See below for choosing the right carburettor size for your car.

Carburettors are available in many different sizes, rated by their maximum flow. Buying a carburettor that is too big for your car will cost you more money than necessary, whereas a carburettor that is too small for your car will not give you the performance your engine is capable of.

Try our carburettor size calculator to find the best carburettor for you. Type in your engine size and type, as well as the highest RPM. Then press calculate to see the optimum carburettor size:

Engine Size:
Engine Type:
Maximum RPM:
Aspiration:

Best Carburettor Size:

Next, you need to choose whether a vacuum secondary or mechanical secondary carburettor will be best for you. Vacuum secondaries usually work best for heavy vehicles, vehicles with street gearing, automatic transmissions, and engines with more low-down torque. On the other hand, mechanical secondary carburettors work best for lighter vehicles, vehicles with strip gearing (4:11 or higher), manual transmissions, and engines built for high-end power.

Carburettors with mechanical secondaries must be chosen very carefully, as a carburettor that is too big will result in "bog" or "sag". On the other hand, a carburettor that is too small will give better acceleration times, but power may fall off at higher RPM. In this case, a bigger carburettor is not necessarily better. To calculate the best size carburettor for a mechanical secondary carburettor, follow these guidelines.

The first thing you need to know is the lowest RPM at which you use full-throttle. In a manual, you should drive around to look at your personal driving, and watch your tacho. In an automatic, use the convertor stall speed (about 1350 RPM for a typical Chevy converter). Typically, a heavier vehicle with a higher gear ratio (lower numerical ratio) will have a lower RPM rate here. A normal value for a 300 - 400 CID engine is a 650 or 700 CFM carburettor. A lighter car might have a 700 or 750 CFM carbie. To find the exact value, click on the link below and print out the page that opens, or hold a ruler against your screen to connect your minimum full-throttle RPM with your engine size, and extend the line to the carbie size.

Carburettor Graph

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