Need Vacuum Secondary Help

[Oydllay]

Try disconnecting the secondary link from the throttle shaft. Take it for a ride. Bog still there? Not saying your early opening problem isn't possible but its not likely that you are developing too much vacuum. You're right about the black spring. Its pretty stiff and renders the secondary nearly useless. Holley chart is based on stock vac. I'm sure you have at least that assuming your in tune. Any other mods, large cam etc. would drop the vac. and delay opening. Also, don't put a lot of faith in the 4000 rpm in park thing. I can't remember for sure but the secondary servo may be fed ported vacuum developed in the primary venturi. With no load on the engine you may very well be able to get them open at that point. Try diabling the secondaries and verify your problem is not elswhere first.