Engine Maintenance and Modification Bradley Artigue

FIAT 124 Spider
Engine Maintenance + Modification
4. Carburetion
FIAT Spiders manufactured from 1967 through 1980 were equipped with carburetors,
except in California where the 1980 model year introduced fuel injection. Carburetors
were provided by Weber SpA (Italy). FIAT and Weber have a long history; in the 1920s
Eduardo Weber began producing carburetors for conversion kits intended for FIAT
vehicles. His designs were the first progressive twin-barrel types with one barrel smaller
than the other. Various updraft, downdraft, and sidedraft designs were produced by
Weber and the carburetors were installed on vehicles ranging from small engine street
cars to twelve cylinder racing cars. Weber carburetors are still used today in off-road,
racing, and street applications.
4.1 Understanding Carburetors
An easy way to understand how a carburetor works is to study a very simple type, the
single-barrel, updraft carburetor. After this brief introduction we’ll work through
subsequent improvements to arrive at carburetors similar to the one on your FIAT.
F
A
B
E
D
C
Figure 2: Updraft Carburetor. A Float Chamber Vent , B Fuel Bowl or Chamber, with Float , C Spray Tube,
D Fuel Jet , E Venturi , F Throttle
Referring to figure 2, an updraft carburetor has the following features:
• A fuel bowl or chamber (A) in which a float-controlled needle valve keeps the
fuel constantly at a level 5-6mm lower than the fuel in jet (D).
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