Non-CC Q-Jet help needed>>
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Joined: Jul 1999
Posts: 272
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From: Tucson, AZ
Car: '82 Camaro
Engine: 383
Transmission: TH-350
Non-CC Q-Jet help needed>>
I just rebuilt a non-cc Q-Jet and put it on in place of my Edelbrock. Everything is fine but the idle is way too high. With the idle speed screw out all the way (primary blades totally shut) it idles at 750 rpm in gear. Ok maybe that is not super high but it shouldn't be that high with the primaries shut, I would think it would choke it off enough to kill the motor. Also the idle mix screws have no effect to speak of. I have them all the way in and it doesn't make much difference, I think it is still idling rich. The other strange thing I noticed was some raw gas came out of the rear manifold vacuum port (right next to the where the power brake vacuum line goes in) when I pulled that hose.
I didn't have any problems like this with the Edelbrock so I assume it is related to the carb. I had the primary throttle shaft rebushed and the shop didn't do a superb job of getting the blades back in but I don't THINK that they are off enough to allow the thing to idle so high...but maybe that is the problem. Any thoughts? Thanks.
I didn't have any problems like this with the Edelbrock so I assume it is related to the carb. I had the primary throttle shaft rebushed and the shop didn't do a superb job of getting the blades back in but I don't THINK that they are off enough to allow the thing to idle so high...but maybe that is the problem. Any thoughts? Thanks.
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Joined: Sep 1999
Posts: 7,072
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From: Philly, PA
If fuel can get out, air can get in. Usually, unless the throttle blades are badly misaligned, a high idle is the result of a vacuum leak.
The idle misture screws having no effect is odd. Most QJets (stock) have very lean idle circuits. Once you're down below about 2-3 turns open on the mixture screws it should start getting lean enough to slow the idle and eventually cause a lean miss if you keep going.
Another possibility..........
The SECONDARY throttle plates may not be aligned properly. They should seat TIGHT in their bores with almost no light visible past them (carb base plate off carb and held up to the light). The edges of the secondary throttle plates are actually beveled so they seat snug in their bores when fully closed. If you have a plate slightly cocked in it's bore it's like running around with the throttle slightly open. Idle will be high (usually rough, too) and will also be very rich since the secondary calibration is very rich for full throttle performance. I've seen this quite a few times. And since your throttle shafts/plates have been messed with it's a definite possibility.
The idle misture screws having no effect is odd. Most QJets (stock) have very lean idle circuits. Once you're down below about 2-3 turns open on the mixture screws it should start getting lean enough to slow the idle and eventually cause a lean miss if you keep going.
Another possibility..........
The SECONDARY throttle plates may not be aligned properly. They should seat TIGHT in their bores with almost no light visible past them (carb base plate off carb and held up to the light). The edges of the secondary throttle plates are actually beveled so they seat snug in their bores when fully closed. If you have a plate slightly cocked in it's bore it's like running around with the throttle slightly open. Idle will be high (usually rough, too) and will also be very rich since the secondary calibration is very rich for full throttle performance. I've seen this quite a few times. And since your throttle shafts/plates have been messed with it's a definite possibility.
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