How Can I Tell What Size My Demon Carb Is?

by Dan Ferrell
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The line of Demon carburetors were designed for high engine performance on the street and on the track. A product of the Barry Grant company, a fuel system manufacturer, Demon carburetors come in different sizes and design variations for stock replacement, muscle car increased performance and other road racing and marine applications. Moreover, each carburetor application is available in a variety of sizes. Here, you can identify the size of your Speed Demon series carburetor.

Step 1

Open the hood and loosen the butterfly nut from the top of the air filter housing, on top of the carburetor. Use a pair of slip joint pliers, if necessary.

Step 2

Remove the butterfly nut and remove the air cleaner assembly from the top of the carburetor.

Step 3

Look over your Demon carburetor where you will see the choke tower. This tower encloses the primary throttle bores. Next to the choke tower, you will find a set of two secondary throttle plates.

Step 4

Look for a single digit located on the circular perimeter, which circles the first and secondary throttle assembly and serves as the base for the filter housing of the cleaner assembly. This single digit is engraved on the circular perimeter between the two secondary throttle plates. Here you will find a number 6, 7 or 8.

Step 5

Find out which of the two types of boost venturi you have installed in the secondary throttle plates of your Demon carburetor. The boost venturi is the small cylinder or cup sitting on top of each secondary throttle plate. This small cylinder has either a small straight shaft, with annular booster venturi or an angled shaft, with downleg style booster venturi on the side.

Step 6

Identify the size of your demon carb as follows. You have a 575 size demon carburetor if it comes with a 6 digit and annular venturi. If it has the downleg venturi, it is a 650 size. You have a 700 size demon carburetor if it comes with a 7 digit and annular venturi. If it has the downleg venturi, it is a 750 size. You have an 850 size demon carburetor if it comes with an 8 digit and annular or downleg venturi.

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