CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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Secondary,take a long time to open, do they open fast while driveing?
hi, if I take the air cleaner off and look at the carb I have to almost redline the motor before the secondarys start to open, is that normal? do they open faster when driving? thanks
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I could be totally off on this, but its my understanding that while the car is in park or neutral, basically under no load, theres not enough vacuum generated in the manifold to open the secondaries....Thats how i understand it anyway. Please someone correct me if im wrong.
Put the rear up on stands, put it in drive and try it again.
It is actuall because there is too much vacuum in the manifold that holds them closed. When you slam the throttle down under a load the vacuum drops to 0 and the secondaries open. If there is no load the engine will rev up fast enough to keed a vacuum and hold the secondaries closed.
The more I think of it yeah, that really makes alot more sense. Cause if you drive a car that is supercharged or whatnot and watch the gauge, when you step on it you see the needle come out of vacuum, past 0 and into boost. but when idlin or cruisin you're in the vacuum area.
Which poses another question, not one that really makes any difference, but on an NA car.. at WOT for example, you're out of vacuum in the manifold....is 0 the relative stopping measurement point? Or does it go on to create some minute measurement of boost? Sorry if this doesn't make any sense or is a stupid question. It sorta makes sense in my mind but don't know how to convey it properly.
Originally posted by Apeiron Spring tension holds the secondary air valve closed, not vacuum.
That is true @ sustained WOT. Transition from part-throttle to full throttle is a different story. You have a vacuum brake that has a 2-3 second delay built into it that allows for a smooth transition. A performance version will be drilled to allow for a 1 second pull-off.
