Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Poor MPG's

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tony79gmc:
I inherited my dad's 79 GMC Caballero with a 4.3 V6 we put in several years ago. It has a Q-jet 17084226 on it right now. It gets very poor gas mileage with a lot of black sout in the tail pipe. What would you recommend to lean this carb to improve gas mileage.

Cliff Ruggles:
What is the history on the carburetor, rebuilt, when, by whom, unknown, etc?.....Cliff

tony79gmc:
It was orgianaly on a 305 that was in the vehicle when dad purchased it, then we put in on the 4.3. I tried to rebuild it about 4 years ago. Dad wanted larger main jets so we changed them. I don't remember what size. I have the original jets they are 73, everything else is stock as far as I know.

Cliff Ruggles:
I would put the original 73 jets back in it.  I would install one of our kits while it is apart to insure the internals are up to par for this new fuel.  While it's apart remove the aluminum plug over the APT screw.  Tap it for a 3/8" set screw (provided in our kit by request).   Make sure the primary power piston metering rod hanger arms are level and EXACTLY even.

Then you will have full control of part throttle A/F from rich to lean.  The carb should be using "M" series primary metering rods which are tapered .010" on the upper section

This will restore the carb to correct working order and get the fuel mileage back where it should be.....Cliff

tony79gmc:
What is the correct float level for this carburetor?

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