Nine different types of carburetors have been used. These include:
Autolite 1100CHOKE PLATE PULL-DOWN CLEARANCE
- Determine that the fast idle speed adjustment has been properly set. Remove the air cleaner and position the fast idle adjusting screw on the highest step of the fast idle cam.
- Insert a drill of the specified thickness between the lower edge of the choke plate and the wall of the carburetor air horn.
- With the drill properly positioned, hold the choke plate in position and adjust the plastic nut on the choke pull-down rod until it contacts the swivel on the choke lever assembly.
See Figures 1 and 2
- Remove the carburetor air horn and gasket from the carburetor.
- Measure the distance from the gasket surface of the air horn to the top of the float. If the measurement is not within the specified tolerance, bend the float arm tab as necessary to obtain the specified dimension. Be careful not to exert any pressure on the fuel inlet needle, as this will damage it and result in an improper fuel level within the float bowl.
- Install the carburetor air horn to the main body of the carburetor, using a new gasket.
Carter YFDECHOKE CLEARANCE
See Figure 3
- Remove the carburetor air cleaner.
- Hold the throttle plate to the full open position while closing the choke plate as far as possible without forcing it. Use a drill of the proper diameter to check the clearance between the choke plate and air horn.
- If the clearance is not within the specified limits, adjust it by bending the arm on the choke trip lever. Bending the arm down will increase the clearance, up will decrease it. Always check the clearance after making any adjustments.
- If you have made an adjustment with the carburetor on the engine, adjust the idle speed, fuel mixture, and dashpot (if so equipped).
- Remove the carburetor air cleaner and the choke thermostatic spring housing.
- Bend a section of 0.026 inch diameter wire gauge at a 90° angle approximately 1 / 4 inch from one end.
- Insert the bent end of the wire gauge between the choke piston slot and the right-hand slot in the choke housing. Rotate the choke piston lever counterclockwise until the gauge is snug in the piston slot.
- Exert light pressure upon the choke piston lever to hold the gauge in position. Check the clearance with a drill of the diameter of the specified clearance between the lower edge of the choke plate and the carburetor bore.
- Choke plate pull-down clearance may be adjusted by bending the choke piston lever as required to obtain the desired clearance. It is recommended that the choke piston lever be removed prior to bending, in order to prevent distortion of the piston link.
- Install the choke thermostatic spring housing and gasket, and set the housing to the proper specification.
- Position the fast idle screw on the kick-down step of the fast idle cam against the shoulder of the high step.
- Adjust by bending the choke plate connecting rod to obtain the specified clearance between the lower edge of the choke plate and the carburetor bore.
- Remove the air horn and gasket from the main body of the carburetor.
- Fabricate a float level gauge of the specified dimension. (Most kits include a prefabricated float level gauge.)
- Invert the air horn assembly. Check the clearance from the top of the float to the bottom of the air horn, using the float level gauge. Hold the air horn assembly at eye level when checking the float level clearance. The float arm should be resting on the needle pin. Bend the float arm as necessary to obtain the specified clearance, but exert no pressure on the needle when adjusting the float level, and do not bend the tab on the end of the float arm.
- Reinstall the air horn assembly, using a new gasket. This dry float level adjustment is the final adjustment of float level for this carburetor.
See Figure 4
This procedure is the same as that for the Carter YF carburetor.AUTOMATIC CHOKE THERMOSTATIC SPRING HOUSING
- Remove the air cleaner assembly from the carburetor.
- Loosen the thermostatic spring housing retaining screws. Set the spring housing to the specified index mark and tighten the clamp retaining screws.
- If no other carburetor adjustments are required, install the air cleaner assembly on the carburetor.
Follow the procedure for the Carter YF carburetor.DECHOKE CLEARANCE
The procedure given for the Carter YF carburetor also applies to this type, except that the adjustment is made by bending the tang on the throttle lever.FLOAT LEVEL ADJUSTMENT
The carburetor is removed from the vehicle for this procedure.
- Remove the fuel bowl and its gasket.
- Invert the main body of the carburetor, so that the float assembly is pressing against the inlet needle and seat. Measure the vertical distance between the main body casting surface for the fuel bowl and the raised tips formed on the outer ends of the float.
- Measure for the specified setting at both ends of the float. If it is necessary to equalize the measurement, hold the float lever securely with needle-nose pliers at the narrow portion, and twist the float as required. While holding the float lever, adjust the float to the specified setting, while holding the tab of the float lever away from the inlet needle.
- Replace the gasket and fuel bowl. Install the carburetor if no further adjustments are required.
See Figures 5 and 6
Refer to the procedures listed for the Carter RBS carburetor.CHOKE PLATE PULL-DOWN
- Remove the air cleaner.
- With the engine at its normal operating temperature, loosen the choke thermostatic spring housing retaining screws and set the housing 90° in the rich direction.
- Disconnect and remove the choke heat tube from the choke housing.
- Turn the fast idle adjusting screw outward one full turn.
- Start the engine. Use a drill of the specified diameter to check the clearance between the lower edge of the choke plate and the air horn wall.
- To adjust the clearance, turn, the diaphragm stopscrew (located on the underside of the choke diaphragm housing); clockwise will decrease the clearance, counterclockwise will increase it.
- Connect the choke heat tube and set the choke thermostatic spring housing to the proper specification. Adjust the fast idle speed to specifications.
- Loosen the choke thermostatic spring housing retaining screws and position the housing 90° in the rich direction.
- Position the fast idle speed screw at the kick-down step of the fast idle cam. This kick-down step is identified by a small V stamped in the side of the casting.
- Be sure that the fast idle cam is in the kick-down position while checking or adjusting the fast idle cam clearance. Check the clearance between the lower edge of the choke plate and the wall of the air horn by inserting a drill of the specified diameter between them. Adjustment may be accomplished by turning the fast idle cam adjusting screw clockwise to increase or counterclockwise to decrease the clearance.
- Set the choke thermostatic spring housing to specifications, and adjust the antistall dashpot, idle speed, and fuel mixture.
This preliminary setting of the float level adjustment must be performed with the carburetor off the engine.
- Remove the air horn and see that the float is raised and the fuel inlet needle is seated. Check the distance between the top surface of the main body (with the gasket removed) and the top surface of the float. Depress the float tab to seat the fuel inlet needle. Take a measurement near the center of the float, at a point 1 / 8 inch from the free end. If you are using a prefabricated float gauge, place the gauge in the corner of the enlarged end section of the fuel bowl. The gauge should touch the float near the end, but not on the end radius.
- If necessary, bend the tab on the end of the float to bring the setting within the specified limits.
- Bring the engine to its normal operating temperature, park on as nearly level a surface as possible, and stop the engine.
- Remove the air cleaner assembly from the carburetor.
- Remove the air horn retaining screws and the carburetor identification tag. Leave the air horn and gasket in position on the carburetor main body. Start the engine, let it idle for several minutes, rotate the air horn out of the way, and remove the gasket to provide access to the float assembly.
- With the engine idling, use a standard depth scale to measure the vertical distance from the top machined surface of the carburetor main body to the surface of the fuel in the fuel bowl. This measurement must be made at least 1 / 4 inch away from any vertical surface in order to assure an accurate reading.
- Stop the engine prior to making any adjustment to the float level. Adjustment is accomplished by bending the float tab (which contacts the inlet valve) up or down, as required, to raise or lower the fuel level. After making an adjustment, start the engine and allow it to idle for several minutes before repeating the fuel level check. Repeat as necessary until the proper fuel level is attained.
- Reinstall the air horn with a new gasket and secure it with the screws. Install the identification tag in its proper location.
- Check the idle speed, fuel mixture, and dashpot adjustments. Install the air cleaner assembly.
See Figure 7
- Remove the air cleaner and the choke thermostatic spring housing.
- Bend a wire gauge of 0.036 diameter at a 90° angle approximately 1 / 8 inch from one end.
- Block the throttle about halfway open and make certain that the fast idle cam does not contact the fast idle adjusting screw. Insert the bent end of the wire gauge between the lower edge of the piston slot and the upper edge of the righthand slot in the choke housing.
- Pull the choke piston lever counterclockwise until the gauge is snug in the piston slot. Hold the wire gauge in place by exerting light pressure on the choke piston lever. Check the clearance between the lower edge of the choke plate and the air horn wall. To obtain the proper clearance, turn the choke plate clevis adjusting nut as required.
- Install the gasket and thermostatic spring housing on the choke housing. Install the retainer.
- Rotate the spring housing counterclockwise (rich direction) to align the center index mark on the choke housing with the index mark on the spring housing.
- Rotate the spring housing an additional 90° counterclockwise and tighten the retaining screws. Check the clearance between the front of the choke plate and the air horn wall. If adjustment is required, turn the fast idle cam lever adjusting screw inward to increase the clearance, or outward to decrease it. Be certain that the adjustment is made with the fast idle screw at the index mark of the fast idle cam.
- Position the fast idle screw on the second step of the fast idle cam.
- Set the thermostatic choke housing to the specified index mark and tighten the retaining screws.
- If these adjustments were performed while the carburetor was installed on the car, perform an idle speed and fuel mixture adjustment. If so equipped, adjust the antistall dashpot.
Refer to the procedures for this adjustment on the Autolite 2100 two-barrel carburetor.Autolite (Motorcraft) 4300 4 BBL
See Figures 8 and 9
The procedure listed for the Carter RBS one-barrel carburetor also applies to this model.FAST IDLE CAM CLEARANCE
The procedure for this adjustment on the Autolite 2100 carburetor also applies to this model.DECHOKE CLEARANCE
Follow the procedure given for the adjustment of dechoke clearance for the Carter YF Carburetor. Adjustment to the Autolite 4300 is accomplished by bending the pawl on the fast idle speed lever forward to increase or backward to decrease the clearance.FUEL LEVEL FLOAT AND AUXILIARY (SUPPLEMENTAL) VALVE SETTING
See Figure 10
- Refer to the illustration for details of construction of a tool for checking the parallel setting of the dual pontoons.
- Install the gauge on the carburetor and set it to the specified height.
- Check the clearance and alignment of the pontoons to the gauge. Both pontoons should just barely touch the gauge for the proper setting. Pontoons may be aligned if necessary by slightly twisting them.
- To adjust the float level, bend the primary needle tab down to raise the float and up to lower it.
See Figure 11
- Remove the choke thermostatic housing cap.
- Place the choke plate in the fully closed position by opening the throttle lever to about 1 / 3 throttle, and pressing down on the front side of the choke plate. While holding the choke plate closed, release the throttle lever.
- With the choke plate in the closed position, measure the distance between the flat of the fast idle cam and the choke housing mounting post. If adjustment is required, straighten or bend the choke rod until the desired clearance is obtained.
- Bend a 0.036 inch gauge wire at a 90° angle at approximately 1 / 16 - 1 / 8 inch from one end. Insert the bent end between the lower edge of the piston slot and the upper edge of the slot in the choke housing. Open the throttle lever to approximately 1 / 3 throttle and rotate the choke lever counterclockwise so that the bent end of the wire is held in the housing slot by the piston slot with light pressure applied to the choke lever. Measure the distance between the air horn wall and the lower edge of the choke plate. If the clearance is not to specification, bend the adjusting tab on the choke lever to obtain the specified clearance.
- Install the choke thermostatic housing. Be sure that the bimetallic loop is installed around the choke lever. Set the cap notch to specifications.
- Connect a tachometer to the engine. With the engine operating and the temperature stabilized, set the fast idle screw on the kick-down or second step of the fast idle cam.
This preliminary adjustment, which is accomplished with the carburetor off the car is performed simply by inverting the fuel bowl and checking to see that the center of the float is an equal distance from the top and bottom of the fuel bowl.FUEL FLOAT LEVEL-WET
See Figure 12
- Position the vehicle on a level floor, be sure that the fuel pump pressure is within the specifications, and operate the engine until normal operating temperature has been reached.
- Check the fuel level in each fuel bowl separately. Place a suitable container below the fuel level sight plug to catch any spillover of fuel. Remove the fuel level sight plug and gasket, and check the fuel level. The fuel level within the bowl should be at the lower edge of the sight plug opening 1 / 16 inch.
- If the fuel level is satisfactory, install the sight plug. Do not install the air cleaner at this time.
- If the fuel level is too high, stop the engine, install the sight plug, drain the fuel bowl, refill it, and check it again before altering the float setting. This will eliminate the possibility that dirt or foreign matter caused a temporary flooding condition. To drain the fuel bowl, loosen one lower retaining bolt from the fuel bowl and drain the fuel into a suitable container. Install the bolt and the fuel level sight plug and start the engine to fill the fuel bowl. After the fuel level has stabilized, stop the engine and check the fuel level.
If the fuel level is too high, it should be first lowered below specifications and then raised until it is just at the lower edge of the sight plug opening. If the level was too low, it is necessary only to raise it to the specified level. If either is necessary, refer to the procedures for either adjustment.TO LOWER FUEL LEVEL
- With the engine stopped, loosen the lockscrew on top of the fuel bowl just enough to allow rotation of the adjusting nut underneath. Do not loosen the lockscrew or attempt to adjust the fuel level with the sight plug removed and the engine running because the pressure in the line will spray fuel out and present a fire hazard.
- Turn the adjusting nut approximately 1 / 2 turn in to lower the fuel level below specifications ( 1 / 6 turn of the adjusting nut, depending on direction of rotation, will raise or lower the float assembly at the fuel level sight plug opening 3 / 64 inch).
- Tighten the lockscrew and reinstall the fuel level sight plug. Start the engine. After the fuel level has stabilized, stop the engine and check the fuel level at the sight plug opening. The fuel level should be below specified limits. If it is not, repeat the previous steps, turning the adjusting nut an additional amount sufficient to lower the fuel below the specified level.
- Loosen the lockscrew and turn the adjusting nut out in increments of 1 / 6 turn or less until the correct fuel level is achieved. After each adjustment, tighten the lockscrew, install the fuel level sight plug, and then start the engine and stabilize the fuel level. Check the fuel level at the sight plug opening. Install the sight plug and gasket.
- Check the idle fuel mixture and idle speed adjustments. Adjust the carburetor as required.
Perform steps one, four, and five under the procedure To Lower Fuel Level.Rochester Quadrajet 4MV
See Figure 13
See Figure 14
- Seat the vacuum break diaphragm using an outside vacuum source.
- With the air valve completely closed and the diaphragm seated, measure the clearance between the air valve dashpot rod and the air valve lever.
- The dimension should be as specified. If not, bend the rod at the air valve end to adjust.
See Figure 15
- Hold the choke plate in the closed position. This can be done by attaching a rubber band or spring to the vacuum break lever and a stationary part of the carburetor.
- Open the primary throttle plates to the wide open position.
- Insert the specified plug gauge between the lower edge of the choke plates and inside the air horn wall. The choke rod should be in bottom of slot when checking setting.
- To adjust, bend the tang on the fast idle lever to the rear to increase and to the front to decrease the clearance. It is advisable to recheck the unloader setting after the carburetor is installed on the engine by depressing the accelerator pedal.
See Figure 16
- Remove the air horn assembly.
- With an adjustable T-scale, measure the distance from the top of the float bowl surface (gasket removed) to the top of the float at the toe (locate gauging point 1 / 16 inch back from the toe on the float surface). Do not gauge on top of part number.
When checking the adjustment, make sure the float hinge pin is firmly seated and the float arm is held down against the float needle so that it is seated.
- To adjust, bend the float pontoon up or down at the point shown in the illustration.
- Install a new air horn gasket on the float bowl, then install the air horn.
Carburetors are complex units whose proper performance depends upon the cleanliness of internal and external components and the proper adjustment of all parts. In addition to the usual adjustments made to external components at regular tune-up intervals, it eventually becomes advisable to remove, disassemble, clean, and overhaul the entire carburetor in order to restore its original performance. To overhaul a carburetor, one must first purchase the proper rebuilding kit. It is advisable to read the instructions and study the exploded view of the carburetor thoroughly, prior to the actual removal, disassembly, etc.
When the carburetor has been removed from the car and disassembled, the parts (except for the accelerator pump diaphragm, spark control valve, power valve, secondary operating diaphragm, antistall dashpot, and the carburetor solenoid, if so equipped) should be soaked in clean carburetor cleaning solvent, rinsed in clean kerosine to remove all traces of the cleaning solvent, and dried with compressed air to remove all traces of dirt from all passages. The use of rags should be avoided. Drills, wire brushes, and similar tools should never be used for carburetor cleaning. All traces of old gaskets should be removed from the parts prior to reassembly.
When reassembling any carburetor, all of the applicable new parts in the rebuilding kit should be used. One carburetor rebuilding kit is usually used for several different types of carburetors. There may be parts in the kit which are not applicable to your particular carburetor. Check the choke shaft for grooves, wear, and excessive looseness or binding. Inspect the choke plate for nicked edges and freedom of operation. Make sure that the automatic choke housing and piston are clean and the piston moves freely when installed in the housing. Check the throttle shafts in their bores for excessive looseness or damage and make sure that the throttle plates-when installed-close properly.
The float should be checked for leaks by immersing it in water which has been heated to just below the boiling point and watching carefully for bubbles. If bubbles appear, the float is leaking, and should be replaced. When installing the float, check for binding on its shaft. If binding occurs, check the shaft for grooves or damage, and replace it if necessary. When the float is installed, check its adjustment with the tool which is included in the carburetor rebuilding kit.
All stripped screws and nuts should be replaced, as should any distorted or broken springs.
If any gasket mating surfaces show damage, the part(s) involved should be replaced.
On carburetors equipped with an antistall dashpot, the rubber boot should be carefully checked for proper installation in the groove of the stem bushing. Check the stem movement for smooth, free operation and replace the assembly if it is damaged. Do not lubricate the stem.
REMOVAL & INSTALLATION
See Figures 17 through 33
- Remove the air cleaner.
- Remove the throttle cable or rod from the throttle lever. Disconnect the distributor vacuum line, the fuel line at the inline fuel filter, and the choke heat tube at the carburetor.
- Disconnect the choke clean air line from the air horn.
- Remove the carburetor retaining nuts. Pull the carburetor straight up to remove it from the intake manifold. If the fuel in the float bowl is to be examined for contamination, keep the carburetor in the right-side up position.
- Remove the carburetor mounting gasket, the spacer (if so equipped), and the lower gasket from the intake manifold. Discard these old gaskets.
- Thoroughly clean the gasket surface of the carburetor, spacer, and intake manifold. Place the spacer (if so equipped) between two new gaskets and then place the spacer and gasket assembly on the intake manifold.
- Place the carburetor onto the space (if so equipped) and gasket assembly, and install the retaining nuts. Alternately step-tighten the nuts.
- Connect the fuel line at the inline fuel filter, throttle cable, choke heat tube, and distributor vacuum line.
- Connect the choke clean air line to the air horn (if so equipped).
- Perform the preliminary adjustments of idle speed and mixture settings. On carburetors not fitted with plastic limiter caps on the idle mixture adjusting screws, turn these screws clockwise until they lightly seat, and then turn them counterclockwise 1 1 / 2 turns. Do not tighten the mixture setting screw(s) on any carburetor until they seat hard, as this will damage the tip of the screw and necessitate replacement. On carburetors with limiter caps, the mixture adjusting screw(s) should be turned to the full counterclockwise position. To adjust the idle speed adjusting screw, turn it clockwise until it barely contacts the screw stop on the throttle shaft and lever assembly, and then turn the screw clockwise another 1 1 / 2 turns. Be sure that the dashpot (if so equipped) does not interfere with the operation of the throttle lever.
- Start the engine and bring it to its full operating temperature. This may be accomplished by letting it run at high idle (approximately 1,500 rpm) for 20 minutes. When it is fully warmed, stop the engine.
- Make sure that the ignition timing and distributor advance and retard are in proper adjustment before attempting the final carburetor adjustments.
- On manual-shift cars, the carburetor idle adjustment should be made with the transmission in neutral. On automatics, the transmission should be in Drive for the idle adjustment. When adjusting the carburetor with the car in Drive, be sure that the wheels are adequately blocked.
- See that the choke plate is in the full open position.
- Attach an accurate tachometer to the engine, following the procedure recommended by the manufacturer of the instrument.
- Remove the air cleaner, start the engine, and turn the headlights on high beam. On 1964-1969 cars, except 302 V8s with automatic transmissions and 200 cu in. six-cylinder engines, the air conditioning should be on. On all other cars, the air conditioning should be off.
- If your car is equipped with a throttle solenoid, examine the solenoid assembly. It will consist of either an assembly held in place by a bracket with a locknut, a fixed assembly with a nut head on the end of the plunger, or an assembly which can be adjusted by turning a screw in the base of the assembly. Determine the type with which your car is equipped, and adjust it to obtain the correct idle. Bear in mind that the correct idle speed is, in this case, the higher figure of the two-figure specification. (See Engine Performance And Tune-up for idle speed specifications.) Disconnect the solenoid lead wire at the bullet connector and adjust the carburetor throttle stop adjusting screw to obtain an idle that corresponds with the lower figure in the two-figure specification. Connect the solenoid lead wire, open the throttle slightly by hand, and observe that the solenoid plunger follows the throttle lever and remains in the fully extended position while the ignition key is in the ON position. Check the tachometer to be sure that the higher figure in the idle specification is obtained. Install the air cleaner, check this idle speed again, and adjust if the installation of the air cleaner affected the idle. Remember that the final idle speed must be obtained with the air cleaner installed.
- On vehicles not equipped with a throttle solenoid, simply turn the throttle stop adjusting screw to obtain the specified idle. Install the air cleaner, check the idle, and adjust it if necessary.
- To adjust the mixture on carburetors equipped with limiter caps, turn the adjusting screw(s) clockwise until the smoothest possible idle is obtained. On carburetors with more than one mixture adjusting screw, the screws should be turned an equal amount. Remember that you should be making this adjustment with the air cleaner installed.
- On carburetors not equipped with limiter caps, turn the adjusting screw(s) in until the idle begins to drop slightly, and then out. As a general rule, one-barrel (1-bbl) carburetors require one-half to one full turn out, depending upon the point at which the smoothest idle is attained. Two-barrel carburetors usually require about one full turn. (In all cases adjustment is correct when the smoothest possible idle is attained.) Like those carburetors with limiter caps, this must be done with the air cleaner installed.
- Adjust the fast idle by manually closing the choke plate, moving the fast idle cam until the fast idle adjusting screw rests on the proper step of the cam, usually indicated by an arrow on the cam; and adjusting the screw to fast idle specifications. When the adjustment has been made, allow all equipment, which you positioned for the adjustment, to return to its normal position.
- When all other adjustments have been made and checked, the antistall dashpot should be adjusted. First, refer to the accompanying chart to find the proper adjustment for your car. On all carburetors except the Autolite 1100, loosen the antistall dashpot locknut, hold the throttle in the closed position, and depress the plunger with a screwdriver blade. Measure the distance between the throttle lever and the plunger tip. Turn the antistall dashpot in whichever direction is necessary to attain the proper clearance between the tip of its plunger and the throttle lever. Tighten the locknut to secure the adjustment and check the adjustment to assure that it was not altered during tightening. On the Autolite 1100 carburetor, turn the dashpot adjusting screw outward until it is clear of the dashpot plunger assembly. Turn the same screw inward until it contacts the plunger assembly and then turn it in (clockwise) against the plunger assembly. On cars with manual transmissions, three turns in against the plunger assembly are required. On automatic models, two turns will suffice.