Originally Posted by cj5752
The venturies are machined into the carb body. If you look down the throat of the carb you will see it is tapered to a point then becomes wider again. this constriction is the ventury. The taper speeds up the air to make it draw fuel through the jets better. If the venturie area becomes to large for the amount of air you are pulling the air speed drops and you don't get as good of vacuum sinnal at the boosters. At this point throttle response gets worse.
Wow ! That makes sense,
. Even the rebuild kit exploded view identifies part #37 as the venturie boosters. I need to examine all of my boosters.
I don't have an inside micrometer. I could feel the taper you speak of. Upon visual inspection, I can even see casting marks at the taper. They do look different on my 1.21s with the larger butterfly openings but the 1.21 with the same sized butterflies as my 1.08, look the same.