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7/15/17 7:57pm - Original Message: 'quadraget CFM on a L48 Motor'
carls73
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Kingwood, TX - USA

Vette(s):
1973 Stingray 2005 Coupe

Joined: 6/30/2017
Posts: 6
looking for the cfm rating on my 1973 L48 quadrajet, anyone know where I can find the info?
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7/15/17 8:10pm - Reply: 'Re: quadraget CFM on a L48 Motor'
manchestershark Lifetime Member
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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.

Joined: 10/31/2007
Posts: 1898
Most of them are in the 600-650 range.

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7/15/17 8:42pm - Reply: 'Re: quadraget CFM on a L48 Motor'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
Here's some info:

https://www.youtube.com/watch?v=xuqz5Bs96Tw

https://en.wikipedia.org/wiki/Quadrajet

Image result for quadrajet cfm sizes
Some reading:

https://www.motorstate.com/Quadrajet.htm

Hope this helps. Basically the Q-jet is a variable CFM carb up to the maximum of either 750 or 800.  The 800s are fairly rare.


|UPDATED|7/15/2017 6:42:26 PM (AZT)|/UPDATED|


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1973 L-82 4 spd

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7/16/17 8:34am - Reply: 'Re: quadraget CFM on a L48 Motor'
carls73
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Kingwood, TX - USA

Vette(s):
1973 Stingray 2005 Coupe

Joined: 6/30/2017
Posts: 6
thanks for the information, I am in the process of rebuilding mine and am not having much luck right now. seems to be an issue with the power valve because when I adjust the mixture screws not much happens.  
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7/16/17 6:21pm - Reply: 'Re: quadraget CFM on a L48 Motor'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
There's a couple of good books on Qjets, one by HP books and the other by Cliff Ruggles.

At idle the power valve should be down unless there's a vacuum problem.  A good cleanup and rebuild will probably take care of the problem unless there's a vacuum leak somewhere else.  It's surprising (at least to me) how little air an engine uses at idle so a minor leak can have a large effect..


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1973 L-82 4 spd

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7/21/17 2:34pm - Reply: 'Re: quadraget CFM on a L48 Motor'
Sarge81 Lifetime Member
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WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2376
Make sure your primary throttle shaft doesn't have any up, down, front to rear play in it. This will be a source of a vacuum leak. If it does, there is a bushing kit out there that will fix that problem. Very common with Q-jets, especially 4 speed car because of being on and off the gas pedal between shifts. 

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GEN III 5.7L "LS6" Engine swap
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3.54 Dana 44
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7/21/17 11:10pm - Reply: 'Re: quadraget CFM on a L48 Motor'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
Good point.  But it happens to Holleys also.  I bushed my friend's '66 427 Holley.  Really helped.  The kit came w/ a reamer and bushings.

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1973 L-82 4 spd

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