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Discussion Starter #1
I have a 68 gto that I bought a couple of months ago. It is stock with a 70 quadrajet that's got me puzzled. The thing idles really rich (black smoke) and off idle it bogs and backfires unless you slowly bring up the throttle. My idle screws are around 1 1/2 out and the float level is good. The carb has been rebuilt twice, once before I bought it and once after I bought it. All internals look new and clean. Now hear comes the screwy part... if I turn the idle screws all the way in the engine cleans up and STILL RUNS! Also, if I crack the secondaries manually by themselves it has instant response with no issues. Anytime the primaries are involved it bogs and backfires. When I shut it down, almost instantly gas leaks from both sides around the primary rod onto the intake. I assume it almost empties the bowl because it takes alot of cranking to start it after it sits for awhile. When I had it apart and filled the bowl with fuel it did not leak. I suspected too much fuel pressure but under test it was under 7psi. Oh and casting plugs have been epoxied. Any ideas?
 

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To me it sounds like it's still getting way too much fuel. The flow of fuel is never being shut off from entering the bowl. Is the float full of fuel, or, is the needle bad, or, is there debris in the seat that keeps the needle from sealing properly thus allowing fuel to constantly fill the bowl?
 

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Discussion Starter #3
Needle, seat and float (plastic) are new and all clean. I'm not sure if this is supposed to happen but when I was checking the fuel pressure as soon as I shut it down the needle went down to zero in about 5 seconds. Also, there isn't any fuel dripping down the primaries which is one of the reasons this has got me so baffled. It's getting a bunch of fuel but I don't know from where.
 

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New float, but where's the float level and float drop set to? It sounds to me like your float level is waaay to high. You have a new needle and seat, but I've seen debris get in there and raise hell. Start with the float/needle/seat. You're carb is too rich, and the float affects all of the circuits in the carb.
 

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Discussion Starter #5
The kit said 3/16 and I have it set at 1/4 inch, not sure about the drop. The float was put in from the previous rebuild so with that being said could it possibly have the wrong float? Maybe the float is too short and doesn't have enough leverage to shut off the fuel? I suppose I could test that theory by taking the airhorn off, disconnecting my ignition and turning it over.
 

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1/4 is 4/16. Shouldn't matter too much, but it's a possible cause. You need to set the float drop, too. Could also be a fuel saturated (heavy) float. You might want to just replace the float with a new, correct one, set it to specs, and go from there.
 

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Discussion Starter #7
If I remember right the float sat on the bowl when relaxed. So it may be that the needle is getting wedged in the seat and not stopping the fuel because the drop isn't right. I'll have to tear it apart and try that and if that fails get another float. Thanks for all the help you guys!
 
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