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Old 11-23-2011, 05:30 PM
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Quadrajet carb dribbling fuel into primarys

Hello fellow hot rodders, I'm having some issues with my rebuilt carburetor.
17059216 I own a copy of cliffs book and I purchased the complete kit from cliffs high performance, and also got a tuning kit. After very carefully reading over and over I set my float leval to 1/4 the first time according to cliffs book, it leaked so took it back off reset float to 15/32 according to adjustment sheet. still leaked fuel from primaries venturi.

I've done alot of reading on this problem came up wirh float leval to high , wrong float , bad float taking in fuel, I'm lost and I have got almost two hundred dollars into this carb wishing for the ture quardrajet performance ive been told about but still never experience for myself.

Can someone please please help me this is my only opperable vehicle at moment . I was wondering of maybe the needle seat was damaged I took it out it looks ok to me not noticable damage.

one more thing I noticed when the motor is idling the primaries are dry I look down into the slot between primaries and secondaries where you can look straight dowm and see float. I could see liquid on top of it I took my tiny flathead and while running pushed float down and fuel came rushing in and flooded out motor and leaked all over intake so im assuming the needle is seating fully .

Thanks everyone I hope everyone has a great thanksgiving the best day to over eat

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Old 11-23-2011, 05:45 PM
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I don't think I verified that the leaking happens after shut down
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Old 11-23-2011, 07:56 PM
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Quote:
Originally Posted by bigals77
I don't think I verified that the leaking happens after shut down
Does this occur only when the motor is hot or anytime you start the car? If the motor does not flood out when it's running, your floats should be set pretty close. If it leaks only after shut down, I would suspect the needle/seat is not shutting the fuel off and allowing the pressurized fuel in the line to leak past the needle. If it only does it after the motor is hot, it could be that the fuel is getting hot in the bowls. I would look at the needle/seat again, maybe even replace them even though they are new. JUst because they are new, don't mean they are perfect.
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Old 11-23-2011, 08:03 PM
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You either have too much fuel pressure, or not enough ignition timing.
Over 5 psi fuel pressure causes the drip.
Late spark timing causes throttle opening to be off the idle slots and tipped into the primary which also causes the runny nose. What`s the base spark timing set at and is vacuum advance in use?
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Old 11-23-2011, 11:19 PM
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It always helps to say what type/size the engine is, along w/the particulars like compression, cam, intake type, etc. when asking about tuning a carb. Also, DV asked a couple important questions so it will help if you can answer them.

When you say "still leaked fuel from primaries venturi", I am gonna assume you are saying the primary discharge nozzles are what's dripping or leaking fuel at idle. If that is the case it is directly tied to having the primary throttle blades open too far at idle. This allows fuel to be introduced from the main circuit along w/the idle circuit.

To remedy this, you need to determine why the throttle blades have to be open so far for the engine to idle. I would suspect one or more of the following is the cause of the nozzle drip:

the fuel pressure is too high
timing is retarded, causing the primary throttle blades to be open too far at idle
idle mixture too lean, causing the primary throttle blades to be open too far at idle
float level- but I believe you have this covered
power piston spring too strong for the vacuum the engine makes (how "big" is the cam?)

There IS a chance the needle and seat could be causing the float level to fubar. One thing to be sure about is how the tiny hook that's on the needle valve is attached to the float. It should be hooked to the float rear cross piece closest to the power piston- NOT hooked through one of the holes!

Do not be tempted to go too low on the float setting.
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Old 11-24-2011, 12:21 AM
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What about the plugs in the bottom of the main well? Just a thought.

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Old 11-24-2011, 12:48 AM
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The plugs can cause problems, you are right. But they won't cause the nozzles to dribble.

That's a good photo of the main wells being plugged after tapping them, and is what I often recommend. My question is, where did you find that photo? I've googled images before hoping to find something detailed like that and found nothing that good!
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Old 11-24-2011, 10:03 AM
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Seems like every Q-jet I've been into, we end up pluggin' the main wells 'the right way'.

The photo is this:

http://www.mre-books.com/quadrajet/i...leakrepair.gif

From MRE books website article:

http://www.mre-books.com/quadrajet/carbrebuild.html
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Old 11-24-2011, 10:18 AM
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I`ve seen that alot have the issue with the main wells. And I epoxied many which did not stop the leak.
One day I placed the body on a bucket, poured some fuel in the bowl and watched it go to dripping within minutes.
So I took the body, got a hammer and a punch then repeened the main well plugs. Then I placed it back on the bucket and refilled the bowl. No more leaks. Checked them again 6 hours later and the bowl was still full.
Checked it the next several days and the bowl was still full.
So now I do all of them this way and it`s worked every time and it sure beats buying epoxy then having to wait on it to dry only to find out it don`t work.
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Old 11-24-2011, 10:34 AM
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Thanks for the photo and link, C-10.

I have used peening to seal the wells myself. I prefer mechanical
fixes instead of epoxy because I've had Q-jets that the epoxy had
debonded after being put on the well plugs. It'll last longer than
those cheesy foam sponge pieces the kits give to stop the leak,
but epoxy isn't a permanent fix like tapping or peening, IMO.
Ruggles has recommended Marine Tex epoxy, but I've never
tried it. Looks like there's epoxy on the threads in that photo, too.

The photos below show a new main well stop leak sponge on one
side and one removed from a carb I rebuilt about a year ago. The
carb had been in service for about 5 years since it was last rebuilt.

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Old 11-24-2011, 07:36 PM
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Fuel dribbling from the main venturis is caused by fuel pressure overpowering the needle seat assembly, raising the fuel level too high. If the carb is new to the engine and the carb has a high flow seat (larger diameter than previously used), the same fuel pump pressure is likely to force the needle slightly off the seat due to the larger seat area and raise the fuel level until it dribbles out at idle.

Providing that the float is good and adjusted correctly, lower the fuel pressure. If it's a used carb and just started to have problems, it's time for a rebuild with a new needle and seat and new float.
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Old 11-25-2011, 08:08 PM
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Ok it is on a 350 with vortec heads comp 268 cam edelbrock intake and headers on 77 chevy shortwide.not exactly sure on compression ratio...
The problem happened only after shutting off the motor it would leak down the venturi.

I took carb back off this morning took apart took needle seat assembly off vacuum tested it was good, It had a windowed type seat and I changed it back to a solid type seat put new washer under reassembled it all rechecked float leval set at .420 put back on truck it fired right up let truck warm up I look down into carb while idiling primaries staying dry but when I look into that little slot behind primaries that ur can look down and see float, well when I look down their all I see is fuel on top of float andi cant see top of float at all I can stick my tiny screw driver down and gently push float down so I know the float is not stuck down I took it for a drive the shut motor off. I looked dowm into carb and watched for a few minutes never saw any fuel dripping,

I'm still wondering if thats ok for fuel to be seen on top of float, and its also got a lill bit of fuel coming from accelerator pump hole. Its a stock fuel pump on motor

I wonder if I'm suppose to have a return fuel line the pump I'm using does not have it. I'm trying to get this thing fine tuned anf its been dificult the hole way.

Thank you everyone for your replies....
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Old 11-25-2011, 08:12 PM
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float level to high

Had a Dodge v/8 with a carter done the same thing after shut down it was float set to high. Once i fixed it no problem
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Old 11-25-2011, 08:18 PM
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I forgot to mention the seat I'm using is .135 it is a fresh rebuilt carb everything cam from cliff
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Old 11-25-2011, 08:29 PM
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Something that happens more than you might think, is the old seat gasket gets left stuck to the carb then a new gasket is used- making two gaskets total. This will mess w/the float level and can leak at the base of the seat, too. It could have been that way before you worked on it and when you removed one gasket there was still another one in place. Then when you reassembled it w/a fresh gasket you'd be back to two gaskets under the seat.

I mentioned the hook on the needle earlier. If you even use a hook, is it hooked correctly to the cross piece of the float nearest the power piston and not through one of the holes that are on some floats?
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