Purpose of these holes?

[Gaz64]

Originally Posted by Jac Mac

Gary, you should have started 10 years earlier.
Most if not all of the carbs fitted to 6 & 8 cyl Holdens, Chrysler Valiants, and Ford falcons produced in OZ during the 1970's & earlier have similar holes drilled above the throttle plate area. In this particular case with the standard production carbs/engines it was to help prevent fuel pullover from the main venturi when the choke was in operation with the throttle blade in the fast idle position. Strombergs, Carters & Email? carbs, both single & 2bbl had this feature, I will have to have a look at some Autolite/Motorcraft carbs to check, but I think some of them had an internal drilling/passage from above the choke horn to the throttle plate area that performs the same function, plus uses cleaned air. You have to remember that in this instance the carb airflow ratings and venturis were quite small .

Is that right. Let's see some photos.

Sounds like b/s to me.

"help prevent fuel pullover from the main venturi when the choke was in operation with the throttle blade in the fast idle position"......

The choke system, so aptly named, because it strangles the engine for air, it causes the engine to pull fuel from the main discharge nozzle at low airflow, ie: cranking speed.
The choke flap is offset, the flap opens a predetermined amount once the engine fires. The engine may still be partly on the main circuit at high idle.