[MEJ1990TM]

Pulled the Q-Jet off the ‘71 to freshen it up. It ran ok, but was jetted kinda rich for the elevation, and the accelerator pump had dried up. Got it all back together with new gaskets, fuel filter, and the like. No hard parts changed with the exception of the jets, but now it’s flooding. Can only assume I’ve missed something in the assembly, but am having a hard time figuring out what.

You can see where the gasket for the top plate is getting saturated with fuel while the car cranks. Checked ,and double checked, the needle and seat and there was no debris present. Just to try it I put the old ones back in. Made no difference.

I thought maybe I’d forgotten the gasket that goes under the seat, but that wasn’t it. Is there maybe a gasket that goes under the screw that holds the check ball in place down in the body?

I’m open to suggestions.


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[77 cruiser]

New needle & seat with a new gasket? Did set the float level? Where did you put the clip on the needle?

 

[MEJ1990TM]

New needle & seat with a new gasket? Did set the float level? Where did you put the clip on the needle?

Yes, new needle, seat, and gasket. Didn’t adjust the float levels since the car has run for so long with it the way it is, but I suppose it could be worth double checking. I’d feel kinda dumb if that’s what the issue is.


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[David Ray]

To properly set the float in a Q-Jet, one hand has to do two functions, hold the float pin down in its groove with one finger, as it can sit above its groove, setting the float too high. GENTLY hold the float against the seat, set float level at the front of the float. Key here is GENTLY.

Then, there are three different design floats for them, original is brass, second is Nitrphyl (black plastic), last is a white plastic.

Brass can degrade, get pinholes, and sink, partially sink
Nitrophyl can lose its outer coating, saturate and sink, either all the way, or partially for as much fuel volume it has absorbed.
Plastic does the same as Nitrophyl, develops pot holes, sinks, partially sinks

The other place Q-jets leak is on the inderside of the main carb body, at the multiple drilled passage area, where they are simply plugged off. Sealikng the two areas with a good fuel proof epoxy will stop the leaking. These leaks drop raw fuel directly into, and through the base plate, right into the engine. Key give away is stopping the engine, then coming back the next day to fnd the float bowl dead dry empty, and the engine flooded.

 

[427L88]

Don't feel dumb; as that is likely exactly what it is. As Professor Ray describes, you physically seat the needle, oh so gently, and then measure the back of the float to top of carb body for your setting. Typically 5/16" or .300" if I recall. The setting is adjusted by bending the float arms. You ought see a cut in each to give it some flex for this.

Wish I could post a pic out of Doug Roe's book. Worth a 1000 words.

Also, I like to seat the needle a few times gently before install to ensure the mating surfaces are copasetic. Never assume , always verify. Also was 'learned' to keep that flimsy little clip spring on , as it serves to keep the needle up against the float arm for faster fuel filling.It does not go in the slots. ( Don't want to go lean the top of second or third gear!)

You will know right away if it was off. Please report back with findings.
\

>>>>>>>>>>>>>>Tom edited the .200 to .300. 5/16 is .310 or so. .200 is less than 1/4", won't work<<<<<<<<<<<<<<<<<<<,

 

[Johnny Bravo]

 

[427L88]

BOOM.~! Thnx Johnny!

 

[Johnny Bravo]

Not a problem. I haven't had that book open in a long time.😉

 

[MEJ1990TM]

Thanks, guys. I’ll play with it again tomorrow after work. I’ve only ever done one Q Jet, and it was this one eight or so years ago. Could do a Holley with my eyes closed.


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[von]

One common mistake in rebuilding Q jets is to unknowingly leave the old seat gasket in place and adding the new one, causing a leak. They're hard to see and sometimes you need a sharp pick to remove them. Also sometimes the seat gasket surface gets buggered up and the gasket doesn't seal well. You can test for leaks there by putting the needle in the seat, put a soapy water solution around the seat gasket area, gently hold the needle in place, and blow about 10-15 psi of air in the fuel inlet. If bubbles appear you have a leak there. You don't have to seal the air source to the carb, just aim the nozzle loosely in the fuel inlet.

 

[nitrofox]

You can test the needle and seat out of the carb with a hand held vacuum tester. If it'll hold vacuum with just the weight of the needle it's not leaking

 

[MEJ1990TM]

You can test the needle and seat out of the carb with a hand held vacuum tester. If it'll hold vacuum with just the weight of the needle it's not leaking

Was out there with it this weekend, and happened to notice there was a recess for the seat gasket to set into. Without remembering for sure I thought perhaps that’s what I missed, and the gasket wasn’t seated properly. No such luck.

I’ve obviously missed something in putting the carb back together, because prior to this the car ran fine. It just needed to be jetted down a hair. Back to the drawing board!


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[Tom Mobley]

what's the float level?

I haven't installed one of those little clips in 40 years of building Q-jets. if your float level is set OK it's highly likely that the little clip is the problem. there's several ways to install it wrong and it's cause a bind on the needle and it won't seal. the needle must be absolutely free in the bore. Don't install that clip with any part of it in one of the holes in the float. If the carb is running over be sure to have a good fire extinguisher on hand. A burnt down car is one thing, a burnt down house is another.

 

[David Ray]

Just looka them two fingers holding both the float pin down, and the float against the needle, told ya'

 

[MEJ1990TM]

Well, finally got the issue resolved. What I’m pretty sure I did was not have the seat gasket down in the recess at the bottom of the bowl, but that wasn’t the only thing. When the carb was off I’d also gone through the ignition system. New cap, rotor, plugs, and wires. Was out there this afternoon after work and when it would crank it sounded a hell of a lot like it didn’t have any spark.

Before I was a little too fixated on the carburetor being at fault I think ,which it was at first, but I’d remembered when putting the new cap on it didn’t feel 100% right. It still went on ok, but didn’t fit perfectly. Sure enough I put the old cap back on there and it lit right off like it was running yesterday. Visually I can’t tell what’s different in the two caps other than the old one is parts store generic, and the new one is Delco. Not sure why I didn’t think of this sooner. Too focused on the carb it would seem.


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[427L88]

Hey, that's NEVER happened to any one of us! BTDT

How about popping heads off an SBC to do a quickie valve job, only to find it was bad wires! Hey I was in college, all a learning experience.

 

[billdini]

Hey, that's NEVER happened to any one of us! BTDT

How about popping heads off an SBC to do a quickie valve job, only to find it was bad wires! Hey I was in college, all a learning experience.

Gene as long as we learn from our mistakes all is good. Its when we do it again that it’s a problem.

 

[nitrofox]

An old boss use to say, "learn from your wit, and you'll never forget".