Re: Holley vac. sec. question
When we would get cars with vacuum secondary Holleys into our shop for dyno testing, I always made a point of forcing the secondaries wide open at about 5000 rpm on one of the runs to demonstrate how much power they were leaving on the table. It's almost impossible to get a vacuum secondary spring that offers a smooth transition to the secondaries and still allows the secondaries to open fully at the max power point.
One side effect that most folks don't think about is the effect that opening the secondaries has on the vacuum in the primary venturi that controls the opening of the secondaries. The secondaries don't open smoothly from a closed position, but rather they open a bit, then close off some, then re-open at a slow rate.
"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
Semper Fi! L/Cpl Edwin L. "Tim" Craft, B Co 3rd AT's, Khe Sanh Combat Base, February, 1968