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 "rich proof" feature on later QJ secondary side 
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Joined: Sat Aug 24, 2013 7:57 pm
Posts: 152
Location: Frostburg, MD
All,

A friend has a QJ that doesn't respond to metering rod changes.

I remember reading about a feature on some later QJs' secondary that prevented the engine from going richer than stoich. Iirc, tuner even posted a pic of the rear of a carb body so equipped.

I'm not sure if it was here or elsewhere. l have looked and looked, and I'll be danged if I can find the thread. Anyone know of it?
Thanks.
Dave


Fri Nov 13, 2015 2:09 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1702
If there is a plug about 7/16" diameter on the rear of the body, use a sharp punch and a light hammer blow to knock a hole in the center of it so the punch can pry it out. The screw is behind the plug. Just turn it all the way in tight. If you have the carb apart you can plug the passages near where they join the main well with some lead.


Fri Nov 13, 2015 3:24 pm
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Joined: Mon Dec 29, 2014 1:26 am
Posts: 433
Aux air bleed circuit disabled with #6-32 blank plugs.
Image

You can also ID them from the top with the carb assembled by opening the rear flaps. Check out the difference here around the air cleaner stud hole:

Image

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Fri Nov 13, 2015 4:49 pm
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Joined: Sat Aug 24, 2013 7:57 pm
Posts: 152
Location: Frostburg, MD
Many thanks, Gents.

Dave


Sat Nov 14, 2015 10:56 am
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Joined: Mon Dec 29, 2014 1:26 am
Posts: 433
And, if you plug the upper holes like in my first pic, you can then repurpose the adjuster screw in the back into a curb idle air bypass. The 'correct' baseplate/bowl gasket for these carbs blocks a hole that would allow vacuum into the adjuster screw cavity. If you use the 'wrong' gasket (from a non-aux bleed model) with that hole not blocked, the screw will pass idle air from the rear vent boss thing (so, filtered air) down through the baseplate into the manifold.

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Sat Nov 14, 2015 9:00 pm
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Joined: Sat Aug 24, 2013 7:57 pm
Posts: 152
Location: Frostburg, MD
thank you!


Mon Nov 16, 2015 9:30 am
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