Carburetors Carb 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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Old Feb 28, 2017 | 04:36 PM
  #1  
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From: detroit
Car: 84 z
Engine: 350
Transmission: 700
Axle/Gears: auto overdrive
pop!

Just changed out accelerator pump on 4bl. Q-jet and used two gaskets under the horn. Is this why when I stomped to the floor it went died for a half second backfired then continued running? Adjustment issue now? 350 Z, no air or emissions. Runs ok other wise. Help and thanks
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Old Feb 28, 2017 | 04:48 PM
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From: Knoxville, TN
Car: 1988 IROC-Z
Engine: 350 TPI
Transmission: T56 swap ongoing
Axle/Gears: 2.77 9-bolt Posi
Re: pop!

Sounds to me, based on what you describe, that the car went massively lean when you punched it.
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Old Feb 28, 2017 | 05:00 PM
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Re: pop!

Did you attach linkage to the same hole in actuator arm? If you did,......did you check the float level adjustment when carb was apart? Those are 2 things to check. Also , it could be the secondary air plate needs some adjustment( spring needs more tension) to open a tad bit slower.
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Old Feb 28, 2017 | 05:07 PM
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Car: 84 z
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Axle/Gears: auto overdrive
Re: pop!

Nice looking car. and thanks for the tips well look there.
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Old Feb 28, 2017 | 05:08 PM
  #5  
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Car: 84 z
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Axle/Gears: auto overdrive
Re: pop!

ok thanks
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Old Mar 1, 2017 | 07:36 PM
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Re: pop!

thank you and you are welcome.
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Old Mar 1, 2017 | 07:39 PM
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From: Perth Western Australia
Car: 1987 Z28 Camaro
Engine: 305 LG4 4bbl
Transmission: TH700R4
Re: pop!

any reason you used 2 gaskets under the airhorn?

correct me if im wrong but wouldnt that stuff with the metering rod hanger length? as in, youd start off with the needles already sitting higher if not off of the seats?
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Old Mar 2, 2017 | 08:54 AM
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Re: pop!

There should be enough clearance between top of second gasket and bottom of primary metering rod assembly to not lift rods out of jets. I also doubt it would affect the secondary metering rods towards a lean condition. It may change the geometry of the accelerator pump linkage with the increased gasket thickness as you are raising the upper carb assembly.If the float level is lower than it should be.... its possible to affect accelerator pump operation. Spenc....... did you clean or replace accelerator pump ball check valve?

Last edited by hockeyman48; Mar 2, 2017 at 09:09 AM.
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Old Mar 3, 2017 | 12:42 AM
  #9  
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Re: pop!

Originally Posted by Spenc
Just changed out accelerator pump on 4bl. Q-jet and used two gaskets under the horn. Is this why when I stomped to the floor it went died for a half second backfired then continued running?
Known as "quadrabog". Secondary air valves opening too soon.

Assuming all linkages are there that are supposed to be there, check the choke pull-off - when pumped up with a vacuum source other than the engine (like a vacuum pump) and locked on, it should stay pulled in. If it doesn't, that's your problem - replace the choke pull-off.

If the pull-off is okay, then adjust the air valve spring tension.
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Old Mar 3, 2017 | 03:57 PM
  #10  
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From: detroit
Car: 84 z
Engine: 350
Transmission: 700
Axle/Gears: auto overdrive
Re: pop!

For now, all these ideas are on hold as the car is back in it's cold parking space. The air horn gasket was fuel saturated so the double gasket. Maybe the horn was loose. heck. Just ordered a pulse wiper motor from Get Parts U.S. Not to confident about that transaction. Thanks guys.
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Old Mar 11, 2017 | 11:01 AM
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Re: pop!

You may want to check carb top section for flatness (use straight edge) as they can warp from over torqueing the front two bolts into manifold.This may account for gasket leak.

Last edited by hockeyman48; Mar 11, 2017 at 01:36 PM.
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Old Mar 11, 2017 | 11:08 AM
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: pop!

stacking gaskets under the airhorn will change the plunger distance for the mixture control solenoid.

won't cause your issue but you need to either go back to a single gasket or adjust the plunger distance with the lean stop adjustment.
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