FIAT 124 Spider
Engine Maintenance + Modification
35
Figure 32: ADF Dimensions
4.8.6 Weber ADHA
The ADHA is similar to the ADFA except for the secondary barrel, which is vacuum
controlled. This is a hard carburetor to love. Introduced with the 2000cc engine the
ADHA was a small carburetor on the largest of the Spider motors. Although a carburetor
with 23mm and 32mm barrels should be adequate for a 2 liter motor, the jetting, intake
manifold, and array of pollution control devices both on and off of the carburetor resulted
in a fairly uninspiring driving experience.
4.9 Carburetor Tuning
These are the recommended procedures per Weber with some modifications, you will
find the same general steps in any publication on setting up carburetors. Should the
engine fan come on during these steps STOP working (leave the engine running) until it
shuts off. Fans draw current from the alternator, creating a load that will reduce engine
speed and may cause you to make incorrect adjustments. Fans are also dangerous to
work around.
4.9.1 Set Carburetor to Factory Settings
Back out the idle speed screw until it is no longer in contact with the throttle stop lever.
Now turn the screw until it contacts the lever and again 1 ½ turns.
Turn the idle mixture screw (on our carburetors it is typically in the center bottom of the
carburetor body) in until it is fully seated - do not force the screw. Now turn it back out
two full turns.
4.9.2 Start and warm the Engine
Disengage or block the choke open. On automatic chokes you can use a small clamp or
wire to pull the choke mechanism open. The engine should start and run poorly (if it
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