Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Q-jet jetting questions

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WhiteC3:
Hi, I have a 81 Corvette that I'm in the process of removing the troublsome computer  and replacing dist and going to earlier Q-jet. I got a carb from a 76 corvette and would like some advice on jetting and initial set-up. I did run it with 77 jets and 52 rods with orange power piston spring. It ran ok slight roughness at around 2000 rpm and above. I have looked up original jetting for many years of corvettes near my vintage and came up with 77 jets with 52 or 53 rods late 1976-78 and 1979-80 72 jet with 41 rod Would it be better to use the later jetting? Also does anyone know the spring color to use in place of original Gm spring 7029529 as this is the spring that belongs with the 77/52 set-up? I hope to be able to set this carb up after rebuilding it now and only install it once and fine tune. Thanks! Tim

By the way my car is bone stock with only a free flow exhaust and is a 350 w auto trans...

omaha:
this is a hard question to answer.  Might be a good application for a wide band O2 meter to see what is actually going on. My gut instinct says to put in a fatter jet. More detective work needed.  Need more information. Could be something else altogether causing the roughness.   Just my .02 cents.

WhiteC3:

--- Quote from: omaha on November 23, 2009, 08:52:25 PM ---this is a hard question to answer.  Might be a good application for a wide band O2 meter to see what is actually going on. My gut instinct says to put in a fatter jet. More detective work needed.  Need more information. Could be something else altogether causing the roughness.   Just my .02 cents.

--- End quote ---
Thanks I was thinking of using the 77 jets since they are most commonly used for the application. I will stay with the 52 rods, but will have the power tip turned down to proper .026 size. It looks like according to the jetting chart I should use the black power spring.
http://www.corvette-restoration.com/resources/technical_papers/Q-Jet_Carb_Tuning.pdf

Cliff Ruggles:
Those large main airbleed carburetors are very difficult if not near impossible to tune.  Just too much emulsion air on the main system.

I would recomend installing one of our recalibration kits.  It comes with jets, metering rods, and 4 drive in main airbleeds.....Cliff

WhiteC3:
Ok I will call to order a kit. Thanks!

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