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Old 08-17-2012, 05:46 PM   #1
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Quadrajet running Rich

I honestly don't know Squat about Quadrajets.

So we finally fired this Firebird up last night to break in the Cam, get things settled down to set the idle and timing but this thing is really running rich.

Have the idle screws turned dam near all the way in, the choke is NOT stuck and bumped the timing to 12 BTDC which helped on a '67 Firebird 400.

Any thoughts???
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Old 08-17-2012, 05:51 PM   #2
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Have you checked the float level and the float needle and seat?
Too high a float level will cause it to run rich, as will a bad needle valve and needle valve seat that allow fuel to leak by and make the fuel level too high.

You'll need to pull the carb to check and set the float level because it's easer to do it with the carb upside down.

Sweet looking car by the way.
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Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
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Old 08-17-2012, 08:01 PM   #3
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Quote:
Originally Posted by NavyVet View Post
Have you checked the float level and the float needle and seat?
Too high a float level will cause it to run rich, as will a bad needle valve and needle valve seat that allow fuel to leak by and make the fuel level too high.

You'll need to pull the carb to check and set the float level because it's easer to do it with the carb upside down.

Sweet looking car by the way.
Haven't really checked it. The carb was professionally rebuilt by a carb shop we've been using for years. It's the original carb and the engine received a Ram Air IV style Comp Muscle Car Cam at .516 lift. The carb shop has done Pontiac Tri Powers and others for us in the past
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Old 08-17-2012, 10:31 PM   #4
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Quote:
Originally Posted by torquedork View Post
Haven't really checked it. The carb was professionally rebuilt by a carb shop we've been using for years. It's the original carb and the engine received a Ram Air IV style Comp Muscle Car Cam at .516 lift. The carb shop has done Pontiac Tri Powers and others for us in the past
What kind of fuel pump are you using?
Excessive fuel pump pressure will cause the same thing.
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96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 193k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles.
In the paint shop now.
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Old 08-17-2012, 11:17 PM   #5
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Quote:
Originally Posted by NavyVet
Have you checked the float level and the float needle and seat?
Too high a float level will cause it to run rich, as will a bad needle valve and needle valve seat that allow fuel to leak by and make the fuel level too high.

You'll need to pull the carb to check and set the float level because it's easer to do it with the carb upside down.

Sweet looking car by the way.
Quote:
Originally Posted by NavyVet

What kind of fuel pump are you using?
Excessive fuel pump pressure will cause the same thing.
This, also get a vacuum gauge and make sure the idle mixture is set properly I don't know how but I missed the part you said that the idle mixture screws were almost all the way in and still running rich, do you have a pressure regulator on it?
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Old 08-18-2012, 09:58 AM   #6
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More I think about this, the idle mixture screws regulate air not fuel.
All the way in would be rich, but it would only affect idle.
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96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 193k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles.
In the paint shop now.

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Old 08-18-2012, 09:59 AM   #7
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Quote:
Originally Posted by NavyVet View Post
What kind of fuel pump are you using?
Excessive fuel pump pressure will cause the same thing.
Just your average stock fuel pump.
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Old 08-18-2012, 10:27 AM   #8
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Quote:
Originally Posted by NavyVet
More I think about this, the idle mixture screws regulate air not fuel.
All the way in would be rich, but it would only affect idle.
They regulate the amount of fuel gets pulled in by vacuum, to far in and it will idle lean,to far out, rich.
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Old 08-18-2012, 10:36 AM   #9
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I disagree, in is rich and out is lean.
In shuts off air, out lets more air in.
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96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 193k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles.
In the paint shop now.
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Old 08-18-2012, 06:00 PM   #10
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Quote:
Originally Posted by NavyVet
I disagree, in is rich and out is lean.
In shuts off air, out lets more air in.
http://www.motorcycleforums.net/foru...does-work.html

This, in is lean, out is rich. The more open they are the more fuel is aloud to be pulled in by vacuum, and it doesn't make it pull more air, it makes it pull more fuel with vacuum
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Old 08-18-2012, 06:16 PM   #11
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Idle Air Adjustment Needle Valve (Model-A.org)

And this one is just the opposite.

So there are differences.
At any rate here is a link to a pdf about Quadrajets and it states that in is lean as you said.
http://www.lbfun.com/warehouse/tech_...ng%20Paper.pdf

But it's backwards from what I remember from tuning my 66 olds 442.
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96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 193k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles.
In the paint shop now.

Last edited by NavyVet; 08-18-2012 at 06:18 PM.
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Old 08-18-2012, 08:05 PM   #12
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I do have a '67 Factory Service Manual and it says to lean the mixture, turn the screws "Clockwise" and it seems the idle system meters fuel more than air.

It's what I love about GM back in the day!

1. "Drugs"

2. Engineers...... Quote: "We don't have to fix it" "LOL"!!!!

By the way guys, thanks for the links!
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