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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 12-15-2011, 03:49 AM   #1
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Carb spitting gas, car stuttering

I have an 87 Trans Am with a 96 vortec 350, edelbrock performer intake, jet stage 2 quadrajet carb, Comp XR270HR cam, and hedman long tubes. The problem is when the car is revved it has a hesitation and sometimes spits gas out of the top. It also will occasionally not stop running after being shut off. Also, when the car is floored from a stop or in 1st gear it bogs, the RPMs go to redline till it finally shifts. It only does this at this gear at a stop or low speeds. Higher RPMs and it does fine. I believe most of this could be timing related, but also think it may be a carb issue? I posted this in tech but thought I may get some possible answers if it is a carb issue here. I appreciate any and all help.

Last edited by 85T/A350; 12-15-2011 at 04:08 AM.
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Old 12-15-2011, 04:13 AM   #2
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Re: Carb spitting gas, car stuttering

Did this just start happening or were you fiddling with it? Spitting back can be to far advanced. I don't get the second part of your question, are you saying there is poor acceleration from low Revs but OK from higher in the band?
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Old 12-15-2011, 04:37 AM   #3
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Re: Carb spitting gas, car stuttering

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Did this just start happening or were you fiddling with it? Spitting back can be to far advanced. I don't get the second part of your question, are you saying there is poor acceleration from low Revs but OK from higher in the band?
Its a fresh rebuilt motor and has been a problem since it has been put in the car. It equates to poor acceleration but not in that since, I have a large cam with stock torque converter and 2.73s so I know the low end power will be lacking. But what it is doing is when you floor it, it just bogs, the RPMs go up to about redline before it shifts. Basically, the RPMS go up like its accelerating but the car goes no where. However, if you are cruising at say 25mph or higher, and floor it, the car accelerates like it should. And if from a stop, if you just normally drive it does fine. If you try to do a burnout from a stop, the RPMs raise but the car bogs horribly intill it shifts. But if you are going 15-20mph or so around a corner and floor it, it will get sideways with no bog. I know Im not to cear, trying the best I can lol. Im heavily leaning toward most of this being a timing issue.
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Old 12-15-2011, 09:54 AM   #4
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Re: Carb spitting gas, car stuttering

Almost sounds like a TV cable problem...? Your description could be taken a few different ways so Im not sure.

You REALLY need to get a looser stall and better gears in it. I think you can use an S10 torque converter that will swap right in and is a lot looser than factory, do a search on it.

How big is your cam?

This may just be normal considering how tall your gears are how tight your torque converter is. There's a reason people build their whole cars around a camshaft and cylinder heads.

Last edited by InfernalVortex; 12-15-2011 at 09:57 AM.
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Old 12-15-2011, 12:16 PM   #5
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Re: Carb spitting gas, car stuttering

Sounds to me as though you have two problems. The spitting back may be carb related but I would go for the timing being off. The other sounds like a slipping trans, could be TV adjustment as the other poster suggested or the clutches/bands may be toast.

The timing thing is easy to check, there are plenty of articles that tell you how to do that.
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Old 12-15-2011, 12:57 PM   #6
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"quadrabog" [quad-ra-bawg] noun - The effect of a Quadrajet secondary air valve opening too quickly when initially going to wide open throttle. Caused by a defective or missing vacuum break, and/or inadequate tension on the secondary air valve spring. See TGO Technical Article "Tuning for Performance with your Computer-Controlled Quadrajet" http://www.thirdgen.org/quadrajet (the section "Setting the Air Valve (AV) tension on your Camaro or Firebird" also applies to non-computer-controlled Quadrajets). Proper ignition timing should be verified prior to attempting these repairs/adjustments.
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Old 12-26-2011, 08:49 PM   #7
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Re: Carb spitting gas, car stuttering

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"quadrabog" [quad-ra-bawg] noun - The effect of a Quadrajet secondary air valve opening too quickly when initially going to wide open throttle. Caused by a defective or missing vacuum break, and/or inadequate tension on the secondary air valve spring. See TGO Technical Article "Tuning for Performance with your Computer-Controlled Quadrajet" http://www.thirdgen.org/quadrajet (the section "Setting the Air Valve (AV) tension on your Camaro or Firebird" also applies to non-computer-controlled Quadrajets). Proper ignition timing should be verified prior to attempting these repairs/adjustments.
I read that and did as it said. I tuned it till the secondaries were held with zero tension. I went and drove it and it helped quite a bit, but there was still a decent hesitation. I turned it a half turn to somewhere near factory specs and drove again. This made it just as bad as it was in the beginning. Can air valves opening to slowly cause this as well? I believe they may have been opening to slowly, causing the bog. Then when I loosened it to no tension, it got better but was probably opening to soon then causing the slight bog? Then when I turned it a half turn, it may have made them open to slowly again. Only thing I can think of is back it back down to the best feel it gives and look elsewhere. Any thoughts?

Last edited by 85T/A350; 12-26-2011 at 08:53 PM.
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Old 01-01-2012, 11:46 PM   #8
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Quote:
Originally Posted by 85T/A350 View Post
I read that and did as it said.
Did you do this?
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Proper ignition timing should be verified prior to attempting these repairs/adjustments.
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Old 01-05-2012, 12:02 AM   #9
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Re: Carb spitting gas, car stuttering

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Did you do this?
Timing is set to as much initial as the motor will handle and still start. The distributor has been replaced with a brand new one. The accelerator pump shot is working good, choke pull off is working fine. The car runs fine in normal driving and any WOT pulls above 2000rpm. Im not sure what else there is to check on the carb. Im discussing this with you five7 in pms. I figured I would update this to see if anyone else might know a thing or two.
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Old 01-08-2012, 12:08 PM   #10
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Re: Carb spitting gas, car stuttering

Your description of the RPM going to redline, but the engine bogging and the car not moving makes no sense.

If the RPM goes up and you're not engaged in a gear with the tires moving, then your trans is slipping for some reason, clutches or valvebody.

A better description could be very helpful.

As for spitting gas up out of the carb, that is from reversion, backfires in the intake, or misfires - slow burn in the chamber escaping into the intake manifold during overlap.
I would check all of your sparkplugs closely, and also take a close look at your manifold vacuum first before going any further.
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Old 01-08-2012, 02:16 PM   #11
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Re: Carb spitting gas, car stuttering

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Originally Posted by 305sbc View Post
Your description of the RPM going to redline, but the engine bogging and the car not moving makes no sense.

If the RPM goes up and you're not engaged in a gear with the tires moving, then your trans is slipping for some reason, clutches or valvebody.

A better description could be very helpful.

As for spitting gas up out of the carb, that is from reversion, backfires in the intake, or misfires - slow burn in the chamber escaping into the intake manifold during overlap.
I would check all of your sparkplugs closely, and also take a close look at your manifold vacuum first before going any further.
I gave an inaccurate description as for what the rpms were doing. When I posted that it had been awhile since I drove it. What is happening is when you go WOT from a dead stop, the car will spin the tires for a split second then bog badly. Rpms DO NOT rise. This bog occurs from any WOT run from 0-1900 rpm or so. The car idles fine, normal driving is perfect. WOT runs above 2000rpm are strong with no bog. The choke pull off is working fine, the accelerator pump shot is fine.
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Old 01-08-2012, 03:21 PM   #12
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Re: Carb spitting gas, car stuttering

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Originally Posted by 85T/A350 View Post
I gave an inaccurate description as for what the rpms were doing. When I posted that it had been awhile since I drove it. What is happening is when you go WOT from a dead stop, the car will spin the tires for a split second then bog badly. Rpms DO NOT rise. This bog occurs from any WOT run from 0-1900 rpm or so. The car idles fine, normal driving is perfect. WOT runs above 2000rpm are strong with no bog. The choke pull off is working fine, the accelerator pump shot is fine.
If you floor the gas pedal slower and more smoothly do you not get the problem at the low RPM?

Describe your distributor please. Does it have a vacuum advance? and how did you set up the centrifugal advance curve?
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Old 01-08-2012, 03:21 PM
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