QJet Question - Team Camaro Tech
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post #1 of 10 (permalink) Old Aug 8th, 03, 04:33 PM Thread Starter
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It seems as though every old QJet that I mess with has a warped bowl assembly. I was wondering do you guys think that when these old QJets get warped, fuel could get sucked out through those openings where the warpage is worst between the bowl assembly and airhorn?

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post #2 of 10 (permalink) Old Aug 8th, 03, 05:09 PM
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It is a good chance, but, I've seen them leak from the two lead plugs on the bottom of the throttle base.

One would need to clean with lacquer thinner or Brakleen and seal them with JB Weld or epoxy sealer.

One might take the affected units to a machinst friend and have him shave the two surfaces flat to seal.

Thanks for helping with the buy......

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post #3 of 10 (permalink) Old Aug 8th, 03, 06:55 PM Thread Starter
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I used JB Weld on the plugs....No more leaking there!!

My carb just continues to run rich. I have the secondaries wired shut so no fuel from there. The power piston is bottomed out at idle, so the fat part of the 45 rod is fully in the 72 jet. It's just running very rich....enough to burn your eyes and .92 on the narrow band O2 sensor....fuel is coming in somewhere. Fuel pressure regulator is set at 5 PSI so that shouldn't be overrunning the needle/seat....


No problem!!

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post #4 of 10 (permalink) Old Aug 8th, 03, 07:17 PM
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It's the airhorn warping from over tightening. The factory puts plastic washers on the front bolts for a reason. You can support the airhorn with wood and beat on the edges until it is almost straight then use a big flat file for the rest. Remember it does not need to be very tight.
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post #5 of 10 (permalink) Old Aug 8th, 03, 07:36 PM Thread Starter
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Using a straight edge. it looks more like the bowl assembly is warped....at least more than the airhorn.


I don't even know if that's it....All I know is that fuel is coming in from somewhere and I thought that I had eliminated all of the likely places. With the engine barely running and the idle screws almost all the way in and the engine just staying alive and it's running rich...

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post #6 of 10 (permalink) Old Aug 9th, 03, 06:56 AM
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If fuel level is set alittle high, it could be pulling over into the manifold via the secondary needle well. This ia a direct shot to the bowl. Check to make sure the venturi boosters aren't 'fueling' when at idle, as seen but fuel dribbling from them. This would indicate high fuel level.

I remember there being an APT valve in the middle of the bowl to aid idle & off-idle circuits, but, I think this was on '72 & later(?) carbs. Obviously, another carb would help, but, being limited by one really sucks.

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post #7 of 10 (permalink) Old Aug 9th, 03, 07:31 AM Thread Starter
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I have about ten QJets. I just decided to rebuild one from the core pile(I guess that I was bored!).....7029223, which is a 69 truck carb(it's the only non first gen camaro QJet I have). I removed the working 7028213 to use this one.

I set the float at 5/16, the rebuild kit says 3/16 but I always run into bowl overflow when I set it higher than about 5/16. I ran the carb and then pulled it carefully off the intake and popped off the airhorn. The fuel level looked good, it didn't look like it was running over....

I am going to try using two airhorn gaskets and see if that seals it up....If not, I'll get the file out. I really hate troubleshooting a carb that pulls fuel in from "mysterious" locations.

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post #8 of 10 (permalink) Old Aug 9th, 03, 01:29 PM Thread Starter
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I doubled up the airhorn gasket and that seemed to help. I also changed the rods/jets to 46/71. Now that puppy stays right on the lean side of stoich(.30 - .55) at idle and at cruise!!!

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post #9 of 10 (permalink) Old Aug 11th, 03, 10:13 AM
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Good job........

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post #10 of 10 (permalink) Old Aug 11th, 03, 05:57 PM Thread Starter
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I just read your point about the APT. That thing was used in the late 70's? The 67-69 QJets that I have all have a factory set power piston stop. You can see the screw while the throttle body is off, but they sealed that screw with a lead plug. It would be a nice tuning point to have, but you can file the bottom pin on the power piston to get it to seat further down....I guess the other factor would be the spring in determining how fast the carb transitions from idle/cruise to power.

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