Chevrolet 12352838 CARB REM

The carburetor identification is stamped at the body side of the carburetor; the carburetor model code of General Motors Rochester carburetors has a meaning; the first digit of the carburetor model number is actually the number of barrels and then there are specific letters for the kinds of choke. Before making any adjustments, one should verify that the engine is warms up, then tighten the carburetor mounting nuts and intake manifold bolts, make sure the manifold heat valve is not stuck and then perform choke, idle speed and mixture adjustments. Curb idle and mixture settings determine the fast idle speed which is set automatically. In choke rod adjustments the stop screw fixed with the idle cam should be tuned so as to touch the fast idle cam, while there should be clearances between the choke valve and the wall of air horn. The intermediate choke rod adjustments can be carried out by placing the coil lever against a drill bit placed in the choke housing. Vacuum brakes adjustment means having to apply vacuum to the diaphragm, and check the choke valve clearance. Adjustments of auxiliary vacuum brakes come close to these and the adjustment of the choke unloader require measurement of clearance when the throttle is wide open. Float level and drop measurements must be correct for proper performance and accelerator pump has adjustments for the rod to ensure correct pump operation. Next, the bowl vent valve must be set sought after to open at the right idle speed. For specific models, configurations, and settings, use may be needed to set adjustments of versions of float level and fast idle, Choke Valve Position. The Rochester Quadrajet carburetor is two-stage with first and second venturi and with fast idle, choke rod, specially vacuum-breaks and the second throttle plates. Operations such as removals and installation include unbolting of different elements and other features concerning right positioning of gasket. Rejuvenation focuses on detailed wash and inspection and change out of parts with kits offered for extensive restoration.

The carburetor is attached to the top of the intake manifold by two or four nuts. These fasteners can sometimes work loose through normal engine operation and cause a vacuum leak. To properly tighten the carburetor mounting nuts, a torque wrench is necessary. If you do not own one, they can usually be rented on a daily basis. Remove the air cleaner assembly, tagging each hose to be disconnected with a piece of numbered tape to make reassembly easier. Locate the mounting nuts at the base of the carburetor. Decide what special tools or adapters will be necessary, if any, to tighten the nuts with a properly sized socket and the torque wrench. Tighten the nuts to a torque of about 12 ft-lbs. Do not overtighten the nuts, as this may cause the threads to strip. If you suspect a vacuum leak exists at the bottom of the carburetor, get a length of spare hose about the diameter of fuel hose. Start the engine and place one end of the hose next to your ear as you probe around the base of the carburetor with the other end. You will be able to hear a hissing sound if a leak exists. A soapy water solution brushed around the suspect area can also be used to pinpoint pressure leaks. If, after the nuts are properly tightened, a vacuum leak still exists, the carburetor must be removed and a new gasket used. After tightening nuts, reinstall the air cleaner, connecting all hoses to their original positions.

Unplug and reconnect the vacuum hoses to the EGR valve and distributor.

Open the throttle slightly to allow the cam follower to clear the fast idle cam steps.

Back out the idle speed screw until the throttle valves are completely closed in the bore.

Lightly open the primary throttle lever until the link just contacts the tang on the secondary lever.

Ensure that the coil tang contacts the bottom side of the inner face of the choke coil lever pickup arm within the choke housing.

Remove three screws and retainers.

Check that the choke operates freely over its full range of travel.

Screw in the mixture screws equally until the final idle speed (lean drop) is achieved.

First, obtain a repair kit containing the necessary gaskets and items.

Measure the dimension between the end of the slot in the vacuum break plunger lever and the air valve when the air valve is fully closed.

Initially, follow the procedure outlined in the first three steps.

If a carburetor shows significant wear, it may be more economical to replace it with a new or factory reconditioned unit.

Note the position of the accelerator pump rod before removing the pump lever by driving the pivot pin inwards slightly.

Check that the choke rod is at the bottom of the slot in the choke lever.

Connect a tachometer to the engine, ensuring it is at normal operating temperature, and place the transmission in Park or Neutral.

Position the choke coil and cover assembly with a gasket between the cover and housing, ensuring the tang in the coil is placed in the slot of the choke coil lever pick-up arm.

It is often more economical to replace the complete unit rather than dismantle it and replace individual components.

If adjustment is necessary, bend the secondary tang on the primary throttle lever to obtain the specified clearance.

Measure the distance from the top surface of the air horn ring to the top of the pump rod.

Carefully remove all hoses and electrical connections, taking note of their original positions, which can be aided by using tags or coded pieces of tape.

The choke valve should be rotated towards the closed position by turning the external lever counterclockwise.

You should check the dimension between the upper edge of the choke valve and the air horn wall.

Bend the tang on the fast idle lever to achieve the specified dimension.

Repeat the initial steps, break off the caps on the mixture screws, set the idle speed to the initial figure using the solenoid plunger, and unscrew each mixture screw equally until the highest idle speed is reached, reducing the speed if needed to the initial specifications.

Ensure that the air valves are completely closed.

Rotate the cover against the coil tension until the choke begins to close.

Clean all metal parts in a suitable cold solvent, avoiding immersion of rubber parts, plastic parts, the vacuum break assembly, wide-open throttle switch, solenoid, or air horn assembly. Do not probe the jets; instead, blow them through with clean, dry compressed air.

If adjustment is necessary to obtain the specified dimension, the choke lever tang should be bent.

Measure the distance between the upper edge of the choke valve and the inside of the air horn wall.

Hold the throttle valve open with your fingers.

If adjustment is needed, file the end of the lock-out pin, ensuring that no burrs remain afterwards.

Use a suitable hexagonal wrench to loosen the lock screw.

Remove the valve attaching screws and measure the valve and shaft.

Always adjust the choke coil lever.

The idle mixture screws are factory preset and sealed, requiring adjustment only during major carburetor overhauls, throttle body replacements, or if high emissions are detected during inspections.