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I don't think my secondaries are opening anymore....

Torque Junkie

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Torque Junkie Enthusiast

Torque Junkie

Posted
Posted

When I put a new air cleaner on my truck a few weeks ago, I played around with the throttle, fully opening it and I noticed that the secondaries don't move at all, even when wide open.  Also, it doesn't really feel like they're opening either.

I don't know all that much about carbs, so is the opening of the secondaries triggered by throttle placement AND engine rpm, or do they open as soon as the throttle's opened passed a certian point?

Secondly, if they aren't opening, how would I go about fixing it?

FYI, My carb is a Carter AFB, and I don't know the CFM rating of it.

Guest Friz

Guest Friz

Posted
Posted

The secondaries are most likely vacuum operated.

When you nail it, if you hear the big, deep WHOOOO sound, they're opening.

Kansas Kid Senior Enthusiast

Kansas Kid

Posted
Posted

When I had my old Buick with the quadrajet carb on it, the secondaries would never open if I tried what you were doing.  But they would open if I was going down the road and punched it, so yours might act the same way.  Just listen for the sound Friz described, if you can hear anything over your exhaust?  (not sure if you have stock exhaust or not)

Torque Junkie Enthusiast

Torque Junkie

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Posted
Quote: from Kansas Kid on 1:27 pm on June 24, 2001

Just listen for the sound Friz described, if you can hear anything over your exhaust?  (not sure if you have stock exhaust or not)

I'll have to go and give it a try and listen for that...  I think the sound Friz described does happen, but I thought it was just the fan picking up RPM with the engine. Is it pretty loud or something quiet you have to listen closely for?

My exhuast is stock, but the mufflers were rotted out so I just hacked them off and am running straight pipes until I get back from Florida at the end of July (won't be running the truck between now and then) at which time I will be putting a completely new exhaust system on it.

-Mike

76BBSub Enthusiast

76BBSub

Posted
Posted

I'm not sure about the Carter, but on a QuadraJet if you blip the throttle wide open (quickly, don't want to break anything) the secondary "flaps" should just open a bit, maybe 1/4" or so.  The lower butterfly is mechanically opened by the throttle linkage, but the vacuum created by the opening of the butterflies is what opens the upper flaps.  If your carb has vacuum actuated secondaries, which I believe it does, it should be the same.  On a QuadraJet there is a spring the holds tension on the upper flap.  There should be something similar on your Carter, which should be adjustable.

Jeff

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