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Old 09-21-2002, 08:33 AM   #1
sam's 72
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Join Date: Nov 2001
Location: Pasadena, Texas, USA
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Adjusting carburetor??

I put a new Quadrajet ( 4 barrel ) on my truck, I did this about 6 months ago, well, all I have done was took it right out the box and installed it. Well, I would like to try and get a little better milliage out of the engine, it is running rich, I am not sure what all I can try to adjust on the carb. And which way to move the adjustments, I know where the air fuel adjustment is at, just not sure which way to move them. The engine is a stock 305 out of an 86 chevy truck. It is a big time dog, I just installed a 700r4 in the truck, and just looking to try and pinch a litle more fuel milage out of it. Some one help me out here.
Sam
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Old 09-21-2002, 09:30 AM   #2
ChevLoRay
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Location: Benton, AR "The Heart of Arkansas"
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Q-jets have metering rod and jets that can be changed to alter the mixture. The setting of the rods in the bores of the jets can be critical. The steps on the rods are important in this process.

For the initial settings (idle air) I have always started by turning the screws in, until they barely seat. Then, I back them out 2 full turns. I do this on both. At this point, a lot of variables kick in, like state of tune, cam, etc. You can use a tach and adjust the idle air screws to maximize the idle speed, which you can then adjust with the idle speed adjusting screw. Vacuum is another indicator, which means you'd monitor the vacuum and adjust the idle air screws for the highest vacuum.

Like I said, there are a lot of variables working here. Short of what I've said, I hope that others can offer suggestions.

I bought a new Edelbrock 1901 Q-Jet and bolted it on my '69 with original 350 block and a Performer intake. I have made no adjustments except for idle speed.

Good luck.
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