The secondaries on a vacuum secondary carb do not open from idle no should they. Also, they will not open when you wing the throttle with the car in neutral. The open based on the velocity of air going through the primary venturi's.
Most Holley (I am assuming it's a holley) vacuum secondary carb come with the "plain" secondary spring. This is the middle of the range of springs offered. Holley's recomended method for determining which spring to use is to keep going lighter until you feel the distinct opening of the secondary then go one spring stiffer. That feeling of the secondary opening is actually a bog caused by the secondaries opening before the egine can use the additional air flow and actually results in slower acceleration than if you go one stiffer. Lighter cars with lower gears tend to like lighter springs.
You can check to see if the secondaries are opeing by placing a paper clip or a tie wrap (not too tight) on the arm and run the car up through the gears.
