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Old 02-09-2012, 06:04 PM   #1
savatreatabvr
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Mystery Screw on Quadrajet!

Can anyone tell me what this screw does? Its a Quadrajet 17057213.

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Old 02-09-2012, 06:43 PM   #2
rs72z
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Re: Mystery Screw on Quadrajet!

I could be wrong but it looks someone plugged a vacuum port.
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Old 02-09-2012, 07:13 PM   #3
Corts60
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Re: Mystery Screw on Quadrajet!

I agree with rs72z. There is definitely nothing to adjust there.
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Old 02-09-2012, 07:13 PM   #4
savatreatabvr
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Re: Mystery Screw on Quadrajet!

You may be right because I tried turning it and it wouldn't budge!

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Originally Posted by rs72z View Post
I could be wrong but it looks someone plugged a vacuum port.
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Old 02-09-2012, 07:39 PM   #5
ray_mcavoy
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Re: Mystery Screw on Quadrajet!

According to the Rochester Carburetor book by Doug Roe, that's the early form of the APT (adjustable part throttle). The screw adjusts the lower stop for the power piston. That screw was normally adjusted at the factory and then covered with a little press-in plug. The later Q-Jets have the APT system in the fuel bowl.
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