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Author Topic: Initial Settings  (Read 3490 times)

Offline Iggy

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Initial Settings
« on: August 26, 2016, 11:53:25 AM »
I have not rebuilt a Quadrajet since 1990 until last year.  Bought a 1969 Grand Prix and the carb had a couple of flat spots and was a little varnished so I put my skills to the test - turned out great.  Now the problem is I just tore into one for a 1978 C20 454 Camper Special that currently has a Buick Q-Jet on it.  I pulled the carb off of a 1986 K30 (454) parts truck I have to rebuild it and found that the previous owner had messed with the carb and the APT and the Idle Mixture screws were fully seated - I have always used the method of turning them in until lightly seated, and recording those for my initial settings.  Since I cannot do that on this carb, what is a good initial setting for the APT and Idle Mixture screws.  It is a stock 1978 454 (same cam and compression as the 1986) with a TH400 and 4.10 gears, truck will be used to haul my 9-1/2' slide in camper.  Thanks.
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Offline Frank400

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Re: Initial Settings
« Reply #1 on: August 26, 2016, 05:54:33 PM »
Knowing the carb number would help, but if we assume it's a mid eighties carb,  that makes the idle mixture screws metric with very fine threads so minus 3 turns would be a good starting point in my opinion.  Frank.
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Offline Ethan1

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Re: Initial Settings
« Reply #2 on: August 26, 2016, 06:55:27 PM »
 And the APT screws 2 turns out is a good starting point as well.

 Also, Welcome to CHP! 8)
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Ethan

1972 Chevelle

(oo______oo)

Offline Iggy

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Re: Initial Settings
« Reply #3 on: August 26, 2016, 08:30:52 PM »
Thanks, I will start with that.  The carb # is 17085212 if that helps.
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Offline Cliff Ruggles

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Re: Initial Settings
« Reply #4 on: August 29, 2016, 09:48:56 AM »
I certainly you got one of our kits for the 17085212 carburetor, they are very special and unique units and require the correct components for them to work like they are supposed to.

They also used special primary metering rods, and limited access to the APT system.

Most likely the idle screws were fully seated because it was too rich at idle after the last rebuild and highly likely it has the incorrect gaskets in it......Cliff
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Offline Iggy

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Re: Initial Settings
« Reply #5 on: August 30, 2016, 11:44:16 AM »
No kit yet, that is my next step.  It was definitely cobbled together by who ever rebuilt it. 
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Offline Cliff Ruggles

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Re: Initial Settings
« Reply #6 on: September 01, 2016, 09:08:10 AM »
They actually take different parts and settings than other Q-jets.  Dedicated Motorhome/HD Truck carburetors are very specific to their applications, and nothing I know of works better on a 454 in a towing application......Cliff
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