Vacuum secondary spring question

[patrickt]

Originally Posted by RET_COP

I respect patrickt's experienced opinion on preferring the vac sec. for the street...

That was a good post. Here's the problem with vacuum secondary carbs and Cobras: In a light weight car, like a Cobra, it is easier, and safer, to have the secondaries not open as quickly as they should, because, if you go just a little too far past the secondary opening "perfect sweet spot," then the onslaught of acceleration from the secondaries flopping open can be unpredictable, break the wheels loose when they shouldn't, and detract from the overall enjoyment of your car because the acceleration resulting from your foot movement is not consistent . Finding the sweet spot is not always easy because, on a very light car, like the Cobra, one spring might not open the secondaries fully, and the next spring will flop them open too quickly. When this is the case, your choice is to either switch to mechanicals or live with them not opening as efficiently as they could if you had been able to find the "perfect spring" (which you can't). The solution is to have an adjustable vacuum secondary that you can dial in with the turn of a screw (instead of changing out a spring), coupled with a simple, easy to tell method of how far your secondaries are opening. Short of doing this, you have to either "get lucky" with one of the incremental springs being just perfect for you, or you live with the secondaries not running to their absolute full capacity, or you switch to mechanicals. Truth be told, on a street driven Cobra, we have so much power that there is actually very little true difference between a "perfect sweet spot spring" and the spring before it, that it doesn't really matter all that much. And, in fact, before I put on my adjustable vacuum secondary housing, so that I could find that theoretical perfect sweet spot, that is exactly what I did.