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Posted: 11/11/2001 1:46:18 PM EDT
I have 1971 SS Chevelle with a 396ci. Last December I threw a new Edelbrock Q-Jet raplacment carb on it. It's a 785cfm w/ an electric choke. The problem is the carb never kicks down from fast idle. Once the choke opens up the engine is spinning @ 1800rpm at idle, even when its at operating temperature. I thought it might be a vacuum leak, but there doesn't seem to be one.
Link Posted: 11/11/2001 2:30:17 PM EDT
Link Posted: 11/11/2001 2:39:16 PM EDT
It's hooked up, but the diaphram is a little stiff. I'm not at home so I can't really look at it. Is this thing connected to the the fast idle parts? The only carb experience I have has been with Holleys, so I'm a little in the dark.
Link Posted: 11/11/2001 2:43:40 PM EDT
Look to see which screw is holding the throttle shaft open. There is one to adjust off the fast idle cam, and then your regular idle screw. If niether screw is making contact, check your linkage for corrrect travel. If its a vac. secondary, check that no lines are rubbing on the op rod ( holding them open a bit)
Link Posted: 11/11/2001 2:47:35 PM EDT
Link Posted: 11/11/2001 3:01:46 PM EDT
the pull-off is a small vacuum actuator on the side of the carb, correct? So, if its diaphram is rather stiff, it may fail to sufficiently pull?
Link Posted: 11/11/2001 3:12:08 PM EDT
[Last Edit: 11/11/2001 3:10:57 PM EDT by raf]
Link Posted: 11/11/2001 3:13:02 PM EDT
My advice is to lose the Quadrabog for a Holley....difference is like night and day
Link Posted: 11/11/2001 3:28:51 PM EDT
Link Posted: 11/11/2001 3:58:29 PM EDT
Originally Posted By Hunduh: My advice is to lose the Quadrabog for a Holley....difference is like night and day
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I have an intake with a spreadbore flange and cannot use an adapter plate b/c it will screw up the clearance for the cowl induction set up.
Link Posted: 11/11/2001 5:30:11 PM EDT
I've seen this before many times. It's usually caused by a bad ground for the carb (choke) through the spacer/manifold. Try running a ground wire from the choke to the block.
Link Posted: 11/11/2001 8:05:01 PM EDT
Just put a 650 CFM Edelbrock on my friends bronco and it does the same thing. Although it cuts down after about 5 mins or if you drive it for a short time. Also if you are going to replace it with anything get a Demon. Hunduh, I think that is the first time I have ever heard anyone recommend a Holley for street use! IM sure if you get the Edelbrock adjusted it will serve you well.
Link Posted: 11/11/2001 10:52:25 PM EDT
Originally Posted By Steel_Rat: I've seen this before many times. It's usually caused by a bad ground for the carb (choke) through the spacer/manifold. Try running a ground wire from the choke to the block.
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This was stated to me by my old boss (guy I used to work for in high school). Just one question, grounding the choke to the block would be euqally, if not less effective, than gounding it straight to the negative terminal of the battery, correct? I tried this and the damn thing didn't open any faster. My first guess was that the electric choke wasn't getting enough voltage. I haven't tried grounding it to the block b/c I grounded it to the negative terminal of the battery first, assuming that would be more effective (the positive lead comes from the ignition circuit, so the choke isn't getting power unless the car is running).
Link Posted: 11/12/2001 9:40:40 AM EDT
In that case I'd check the sending unit. Basically what you have is a power wire going to the choke, and the other wire goes to ground through the sending unit. Take the wire off the sending unit, and with the ignition turned on, ground the sending unit wire to the block, then lift it. You should be able to see the choke open and close. If it does, replace the sending unit. If not, the problem is in the choke itself. It sounds like you might have used the sending unit meant for a guage instead of a choke.
Link Posted: 11/12/2001 3:57:52 PM EDT
Hold the choke open with your fingers with the engine running then snap the throttle open by hand. If it idles down the fast idle and curb idle settings will be ok. This test kinda takes the choke out of equation. If it still idles fast check the fast idle screw on the choke side and curb idle screw on the linkage side. Dont know if you got a electrical or vacuum solenoid that could increase the idle speed. If so disable it then check again.
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