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.

If there is inconsistency between the information on the Decal label and that in the Specifications, then the information on the Decal label is considered to be correct. Adjustment of the idle speed must be done when the engine is thoroughly warmed up, air cleaner installed unless otherwise directed, with proper ignition timing and dwell angle installed and it is important that all the emission control equipment are operative. To measure engine speed use an external tachometer as per the manufacturer's recommendations. If equipped, loosen the electrical lead from the idle speed solenoid and then turn the base idle speed screw to the 'X' rpm indicated on the emissions label with the shift lever in Drive for automatic transaxle or in Neutral for manual transaxle. Both idle mixture screws receive factory preset and are closed; they are only adjusted at the time of carburetor overhaul, when the throttle body is replaced, or in cases of high emissions registered during inspection. The mixture screws are thus sealed, and to check it, an artificial enrichment procedure using propane gas is required because otherwise it is against the law.

First, uninstall the air cleaner; second, properly unlink the fuel and the vacuum connections of the carburetor; and, finally, take off the choke rod or wire. Subsequently, remove the accelerator linkage and the throttle valve linkage or downshift cable if the car is fitted with an automatic transmission. After that, very tender and slowly, take out all the hoses and electrical connections and it is important to remember the previous position and it may be helped by tags or pieces of colorful tape, coded. Next, take off the carburetor attaching nuts and or bolts, and then, pull out the carburetor up. Do not forget to eliminate the gasket or/and insulator before assembling the doors and jambs. For installation reverse the removal process and make sure to fill the carburetor bowl with fuel this will make it easier when starting and reduce battery draw. Change gaskets and also, while at it, angle trim and check the idle speed and mixture settings as required.

To adjust the carburetor after its removal, first put the cam follower lever on the highest step of the fast idle cam and then turning the fast idle screw in a counterclockwise manner until the primary throttle valves are shut. Subsequently, tighten the fast idle screw until it touches the lever and then turn it in an further three full turns. While the carburetor is in the vehicle, fasten a tachometer to the engine and make certain the engine is at normal operational temperature; shift the transmission to the Park or Neutral. Unclip and unscrew the vacuum hose at the EGR valve; place the cam follower above the highest line of the fast idle cam. Set the fast idle screw for the required fast idle, remake the above connections, disconnect the tachometer, and turn the engine off.

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.

The automatic choke is operated by an exhaust manifold heated coil.