When should my secondaries open
Thread Starter
Melting Slicks
Joined: Apr 2003
Posts: 2,592
Likes: 44
From: Gods Country WI
When should my secondaries open
Had the top of the air cleaner off and wanted to see the secondaries open up. Held the throttle open for a couple seconds but neither the butterflies or the top flap budged. I can't even push the butterflies open with a screwdriver, is this normal or might I have something binding. The car is a 78 w/L48 and stock carb. My son said the tach read 4000 rpm before I let off.
Racer
Joined: Aug 2001
Posts: 473
Likes: 0
From: Raleigh NC
Re: When should my secondaries open (Jeff78)
There are folks on here that are much more knowledgable than me, but it is my understanding that they will not open unless the motor is under load. In other words, sitting in the driveway and hitting the gas is not a good indicator.
Drifting
Joined: Jul 2002
Posts: 1,855
Likes: 0
From: Cocoa Beach FL
Re: When should my secondaries open (Jeff78)
Take it for a drive and get on it hard and you'll know if they are opening or not...you'll hear them. It's as deeper tone. Don't try to open them by revving the throttle in neutral (or park) you'll hurt something! :thumbs:
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: When should my secondaries open (hudman)
In addition to only working on demand there is a secondary lock-out on the fast idle cam/linkage that will not allow the seconaries to open while the choke is on. So if the engine is not fully warmed up or the choke is mal-adjusted the secondaries will not open.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: When should my secondaries open (bluevetteman)
And to add to the caution on the choak lockout on the Quadrajet, you will not be able to manually open the air valve unless the throttle is wide open (don't try this with the engine running unless you put a basket under the block to catch the grenaded parts).
Heel & Toe
Joined: Apr 2003
Posts: 22
Likes: 0
Re: When should my secondaries open (Jeff78)
The secondary air valves will not open as long as there is enough manifold vacuum to hold the vacuum break / choke pulloff in the retracted position. When you open the throttle under load (only), the manifold vacuum drops off and the vacuum break retracts to the same position as when the engine is off, letting the linkage allow the air valves to open as required. The secondary throttle blades will not open if the choke is still active, but you don't want to go there because the power would push you past redline (at least for a couple of seconds!).
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Pro
Joined: May 2003
Posts: 619
Likes: 0
From: winnipeg MB
Re: When should my secondaries open (Rich's78$pit)
crawl in the engine bay, get the wife to lower the hood down on you, then get her to drive on the freeway and nail it. Note: her head will have to be out the window so she can see. If she is mad at you she will slam on the brakes and you and the hood will go in the ditch. On your way out- tear out as many vacuum line and wiring as you can..... :lolg:
