So what controls the secondaries on an autolite 4100 as Barnett indicated they are not adjustable? and what Carbi is recommended. The one boofhead suggested?
There is a spring that controls the opening time on the holleys and the ford carb, however, there are no aftermarket springs for the ford carb to change the timing of the opening and they are designed to open fairly late so you hardly even notice it because it is high in the rpm range . holley makes springs that fit the holleys and quick fuel carbs . those carbs also come with a spring that causes the secondaries to pen fairly late so in most caees, you will get more power lower in the rpm range if you install a lighter spring which allows the secondaries to open sooner and the most common spring that most people install is the white one but in some cases that allows them t open too early causing a slight bog/hesitation when they open so you must test the springs by flooring the car from a stop until it shifts into second . keep installing lighter springs until it bogs slightly when the secondaries open then go up one spring rate and call it a day.
also, it is easy to get jets for holley and quick fuel and they interchange with each other meaning that you ca use holley jets in a quick fuel carb and quick fuel jets in a holley carb, HOWEVER, they do not use exactly the same metering system . this means that a 60 holley jet flows slightly less fuel than a 60 quick fuel jet so when you start jetting you need to use only quick fuel jets or only holley jets or you will never get it jetted right . no one knows wtf quick fuel did this.
Here they are and an estimate of opening time in rpm. They don't rate the white spring because it opens really early.