1974 Chevy Camaro Z28 Quadrajet - Special Q

This Q-jet was dirty but still working well enough when we rolled our '74 Z28 into the CHP shop. With a stouter engine in the works, however, we wanted this mixer in tip-top shape. Sean Murphy begins the teardown by removing the secondary rod hanger; the rods themselves pull right out with it.

Lift the lid, and our Q-jet's internals are in plain view. The top of the power piston assembly protrudes through the air-horn gasket, so be careful when peeling it off. Once the gasket is out of the way, the power piston and the attached primary metering rods pull right out. Don't forget the power piston assembly spring underneath; it might be easier to get at once the fuel-bowl insert and float-and-needle assembly are removed.

The intermediate choke lever disconnects from inside the carb after the intermediate choke shaft and the fast-idle cam are pulled from the side.

Here, the float-bowl needle seat has been removed, as has the pump-discharge ball screw...

...Next to come free are the pump-discharge ball (previous) and the unscrewed main jets.

The main body and the throttle-body can then be separated. The idle needle screws are removed from the throttle-body, as are the old gaskets and the fuel filter in the main body, then both bodies are chemical-dipped and air-blown clean.

Murphy then disassembles the throttle-body assembly. In this shot, the fast-idle cam follower has already been removed, as have the secondary butterfly valves. The secondary blades had never been removed, so the flattened ends of the factory retaining screws had to be ground down before disassembly

The primaries, however, had already been out. Look closely, and you'll see that the throttle shaft has bushings installed to guard against leaks. This is a normal part of SMI's Q-jet rebuild and tuning service.

At this point, the main body is worked over in the media-blast cabinet and then recolored (along with the disassembled air-horn assembly). The throttle-body gets a very light once-over on the sanding wheel, just to make sure its mating surface is true.