Vacuum secondary spring question

[Texasdoc]

Right, I have the spring kit and have been doing that. The instructions say that you shouldn't feel the opening of the secondaries. If you feel it, you will get a bog and should back off to a stiffer spring.

I don't get a bog, but I also feel it when they open. Which is better - feel the opening without the bog, or don't feel them open.

I realize it should be measured with a stop watch to see which one is actually fastest - I just don't have the time (or police free straightaway) to compare now.

I'm going to the Friday night drags at Texas Motor Speedway tomorrow night - if it doesn't rain. I want to get it going as fast as possible. I just want to beat CoralCobra who is going too . I won't have time to compare different springs, so I have to go by concepts. Holley says that the car is faster if you can't feel them open.

[patrickt]

Originally Posted by Texasdoc

Holley says that the car is faster if you can't feel them open.

I believe this to be true. I have an adjustable vacuum secondary on my Holley (see this thread: Theoretical Vacuum Secondary Question ) and my "informal street testing" would seem to back it up. You do have a zip tie on the shaft that shows you how far they're opening, right?

[jhirasak]

You should not feel a bog or a change in the rate of acceleration if the correct spring is used. If you feel a bog, the spring is too soft and allows the secondaries to open too early. If you feel a change in acceleration when the secondaries open, the spring is too stiff and the secondaries need to open sooner. If there is no spring available between these two conditions, I would elect to use the stronger spring and avoid a bog during acceleration.