Quote:
Originally Posted by Z Man
I have an ERA Cobra with a 427 FE and dual 4160 Holleys (600CFMs). !
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Z Man, a
perfectly adjusted vacuum secondary will meet, or exceed, a mechanical secondary in almost all respects -- certainly for a predominantly street driven car. The problem is that changing the springs in the vacuum secondary, and then clearly observing the effect on the secondaries opening, is a real PITA. Add to that the fact that any change in the air cleaner, or running without one,
completely changes the equation, and it becomes real easy to just throw in the towel on vacuum secondaries. All of that could be easily remedied if the carb manufacturer just included a simple opening adjustment and a gauge to measure the opening of the secondaries... but they don't. Fortunately, you can do that if you're so inclined. I have a single vacuum secondary and I have installed an easily-adjustable vacuum canister, along with a tell-tale zip tie to measure secondary openings. It makes adjusting your secondaries about as easy as adjusting your idle. Here's the thread on it:
Theoretical Vacuum Secondary Question