Redo Your Q

Save Your Money and Rebuild Your Old Q-Jet

Mike Petralia Aug 1, 1998 0 Comment(s)

Step By Step

Remove the nine screws from the top and the two (three for pre-’67 carbs) screws on the throttle plate on the bottom.

The accelerator-pump arm must be removed before the lid can be removed. Use a pin punch and tap in the pin toward the air horn. It is not necessary to tap it all the way out, just enough to release the arm.

Next, remove the secondary metering rods by loosening the one screw that holds the hanger in place.

Sean Murphy removed the dead choke pull-off diaphragm and choke rod next. The rest of the choke linkage can be left in place.

Use a screwdriver to gently pry off the top; be careful not to damage the main body.

Once the top plate is removed...

...you can lift out the primary metering rods and float assembly.

Lift out and discard the accelerator-pump mechanism because it will be replaced.

The last item to disassemble is the fuel inlet. Loosen the inlet fitting using a 1-inch wrench and remove the filter and spring. Notice that this spring was incorrectly wedged in sideways.

The throttle shafts were very loose, so they were removed since brass bushings will eventually be inserted. A cold chisel is used to knock off the staked ends of the throttle butterfly screws.

All parts were soaked for one hour in a cleaning solution, and some parts even needed a shot of carb cleaner to remove the hard stuff. The parts were then bead blasted with a fine glass abrasive and finally dipped in a chemical solution that restores a factory zinc finish.

The throttle plate was reamed to accept the brass shaft bushings...

...which were tapped in with a hammer.

This spot on the underside of the main body is notorious for mysterious leaks past the factory lead plugs. Murphy applied some quick-setting epoxy to the area.

The throttle plate is reassembled using all-new hardware. Check for proper throttle opening to ensure the linkage doesn’t bind.

After the new seat assembly is tightened with a wide-blade screwdriver, the new float assembly is installed along with a new accelerator pump. Use some silicone spray or light oil to lubricate the accelerator pump as it goes in.

Use a pair of side cutters to push the accelerator-pump pin back through the arm. Finish the task with a flat-blade screwdriver.

The Rochester Quadrajet carburetor is probably the best-kept secret we Chevy folks have. No self-respecting Mustang hugger is gonna think your car runs hard when you open the hood and reveal a Q-jet. Forget about the hard-core Holley crowd taking you seriously until you wax ’em off the line. With a Q-jet, you can fool almost anyone into thinking your engine is a lo-po stocker and still have an engine that runs hard, idles like a kitten, and responds quicker than your paycheck disappearing on a Friday night. Chevrolet has equipped more engines with Q-jets than all other types of fuel mixers combined, and those who can understand and repair a Q-jet are highly respected individuals. The Q-jet is probably the best carb ever designed for the street. It combines small primary fuel economy with performance, and it can be rebuilt at home in just a few hours with minimal tools and equipment.

Complete rebuild kits can be purchased from any auto-parts store; all you need to know is the vehicle application or carb casting number to get the correct kit. If you don’t want to tackle the rebuild yourself, most shops can usually do it for less than the cost of a new carb. We went to Jones Performance Fuel Systems in Huntington Beach, California. Follow along as shop manager Sean Murphy rebuilds a Q-jet.

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