Those little holes are often added to the primary throttle blades for several reasons and may be drilled by the factory on some models. They are often used for the following: 1. to allow air to bypass the throttle blades for more idle air while allowing the throttle blades to remain closed and not expose the transfer slots. 2. Used with larger cams that don't make enough vacuum at idle to keep idle speed up and steady. 3. To keep the throttle from "sticking" with the blades completely closed.
I don't work on enough AFB's to know if they used drilled throttle plates from the factory on certain models. From a logical standpoint, I wouldn't think this feature would be needed on AFB's with idle air bypass. (the giant center adjusting screw in the center on some AFB's). Nor sure if any of this info helps.
If you install the carb and it won't idle slow enough for your application, then non-drilled butterfly's may need to be installed.
|