Vacuum Secondaries

This is why I don't like those carbs. I've been on the dyno with them and they won't open the secondaries until way past 7k. That was a big block Chevy. Most of the time they won't open until it's way too late, even with the lightest spring in them.

I call them boat anchors and catch hell for it.

This /\ /\ /\

The750 isn't too big. There is no reason to ever run vacuum secondary carbs. Once you get over that metal hurdle of the old school "vacuum sec for street, mech sec for strip" you will be much happier.