DISASSEMBLY
The fuel metering system maintains a direct relationship between fuel flow through main jets (metering and vacuum piston rod height) and throttle plate position. This relationship is preset at factory and should not be altered.
To maintain this relationship while disassembling and assembling carburetor, proceed as follows:
- Place fast idle speed screw on TOP step of fast idle cam
- Scribe a line on pump operating lever and air horn
NOTE: This line will be used as a reassembly reference. DO NOT use the lines already scribed on the lever and housing. They are for manufacturing reference only.
- Remove throttle link-to-vacuum piston limiter lever by removing nylon adjusting nut.
- Place carburetor on suitable stand to prevent throttle plate damage
AIR HORN
- Remove fuel inlet line from filter
- Remove choke clean air pickup tube
- Disconnect choke control from automatic choke lever
- Remove air horn attaching screws
- Remove pump drive rod at throttle lever
- Separate air horn from main body
- Turn air horn upside-down
- Remove float pivot pin, float(s) and float drop limiter
- Remove main and auxiliary (supplements) fuel inlet valve seats and gaskets
- Remove secondary air valve lever pivot pin and rod from damper piston assembly and air valve plate
- Remove air valve damper piston rod and spring
- Remove secondary air valve plates or shaft only if necessary
NOTE: Perform this operation with carburetor removed from vehicle to avoid dropping parts into intake manifold
- Remove secondary air valve plate link from damper lever
- Remove air valve plate screws and slide shaft out of body.
NOTE: Record position of spacers used at each end of shaft
- Lift out air valve plate and attached metering rods
- Remove choke valve by removing valve attaching screws
NOTE: File staked ends of screws before removal. Remove flares from threaded tips to prevent damage to shaft threads
- On models equipped with altitude compensation, disconnect compensation choke plate link
- Remove choke plate, shaft and lever from air horn
CAUTION: Choke lever is attached to shaft with a LEFT HAND THREAD screw
- Disengage pump arm from pump piston
- Remove pump operating shaft clip
- Remove both vacuum limiter lever and pump arm
- Slide shaft out of air horn
- Remove hex head screw attaching fuel bowl vent valve operating rod retainer. Remove retainer and rod
- Remove "C" clip retaining spring on shaft
- Remove spring and plunger assembly
MAIN BODY
- Turn main body upside-down and catch accelerator pump discharge needle and ball as they FALL OUT
- Turn body right side up
- Depress metering rod hanger. Check gap between bottom edge of metering rod hanger and top of vacuum cylinder
- Record this measurement for reassembly reference
- Remove nylon vacuum piston stop from channel in main body (use needle nose pliers)
- Remove main metering vacuum piston and fuel metering rods as an assembly
CAUTION: Do not change setting of piston adjusting screw or metering rod adjusting screw
- Unscrew vacuum piston cylinder and remove cylinder, return spring and guide pin
- Remove main metering jets from fuel bowl
- Remove altitude compensation aneroid assembly (4 screws)
- On altitude carburetors, remove (2) hot idle compensator screws through poppet valve holes. Remove compensator
- On non-altitude carburetors, remove cup plug from carburetor body and then remove compensator assembly as outlined in step 10
THROTTLE BODY
- Remove throttle body-to-main body screws and separate castings
CAUTION: Do not remove idle mixture limiter caps or mixture screws from throttle body
- Remove choke housing cover, gasket and spring
- Remove choke piston lever screw and piston assembly
- Remove primary throttle connecting link from secondary throttle lever
- If throttle plates or shaft are to be removed, file off staking on throttle plate screws. Remove screws and plates and discard screws
- Secondary throttle shaft is made up of two sections. Pull each half out of throttle shaft bores after plate removal
- Remove screw from primary throttle shaft
- Remove fast idle lever and screw
- Slide shaft assembly out of primary throttle shaft bore
- Slide return spring off of primary throttle shaft
NOTE: Remove fast idle cam or its bushing only if necessary. If bushing is to be removed from choke housing and bushing column, assembly must be properly supported or column may bend or break
- Carefully press bushing out of choke housing while supporting assembly
REASSEMBLY
NOTE: Be sure to use new gaskets and seals. Check to see that new gaskets fit properly and all holes and slots are punched in correct locations
THROTTLE BODY
- If throttle plates and shafts were removed, install return spring on one-piece primary throttle shaft
- Slide shaft into shaft bore. Primary bores are the smaller bores, with the secondary bores being the largest
- Place primary throttle plates in respective bores with ground flat edges of plate FACING TOWARD idle mixture screws
- Install retaining screws snug, not tight
- Rotate throttle shaft to closed position
- Tap plate gently so that plate(s) are fully seated in throttle bore(s)
- Hold throttle body up to light. Little or no light should be seen around edges of plates
- Install secondary throttle lock out lever
- Install fast idle speed lever and adjusting screw
- Insert throttle plate return spring tang into recess in throttle body casting
NOTE: Spring should operate in closing direction
- Install return springs on each half of secondary throttle shaft. Hook must be positioned over lever and straight tang on inboard end of shaft
- Insert shafts into respective bores until tang on return spring engages boss
- Rotate halves of shaft in OPPOSITE directions until center key indexes
- Install secondary throttle plates
NOTE: Embossed letter "A" faces UP and TOWARD REAR of carburetor
- Install plate screws snug, but not tight. Position and align secondary throttle plates as outlined in steps 4 throuhg 8
NOTE: Be sure return springs operate in closed direction
- If fast idle cam and bushing were removed, insert choke shaft bushing through choke housing
- Place fast idle cam between housing and bushing column
- Slide bushing through fast idle cam
- Press bushing into column. Be sure to properly support casting and column to avoid breakage
- Condition bushing with 1/4" reamer
- Insert automatic choke shaft and lever in bushing
- Place choke piston in choke cylinder
- Place lever on automatic choke shaft. Install screw and lock washer
- Install hot idle compensator into bypass air intake. Install (2) screws through altitude compensation poppet valve opening and secure
- Install secondary throttle-to-primary throttle rod
MAIN BODY TO THROTTLE BODY
- Place main body on bence with fuel bowl down
- On altitude compensation models, install aneroid assembly and gasket to main body (4 screws)
- On non-altitude models, seal poppet valve hole in casting with 1 1/8" plug
- Install new main body-to-throttle body gasket on main body
- Install throttle body to main body
- Turn assembly right side up
- Install main jets in fuel bowl
- Install vacuum piston cylinder and gasket assembly into main body. Place spring over guide pin so it sits in retaining groove
- Place pin and spring in bottom of cylinder
- Slide vacuum piston over spring
- Position metering piston and metering rods into cylinder and main metering jets. Push assembly to full downward position. Install nylong piston stop in main body channel
- If metering rod adjustment has been accidentally changed, depress metering rod hanger. Use a 3/32" screwdriver to turn vacuum piston adjusting screw and metering rod adjusting screws COUNTER-CLOCKWISE until hanger is fully seated against top face of vacuum cylinder
- Hold metering rod hanger in full downard position; Turn each metering rod ajusting screw CLOCKWISE until hanger just starts to rise
- Turn vacuum piston screw CLOCKWISE until clearance between bottom of hanger and top of cylinder is reached
NOTE: Adjust to clearance recorded at disassembly
- Mount choke-to-throttle lock out lever
- Install pump discharge check ball and weight in correct location in carburetor body
AIR HORN
- Install pump operating shaft into bore in upper body casting
- Mount vacuum piston limiter lever and pump operating arm to shaft end. Install clip
NOTE: If new pump arm is being installed, see Accelerator Pump Adjustment
- Install pump assembly on arm
- Install vent valve plunger, spring and clip
- If choke valve and shaft were removed, slide shaft through holes in air horn
- Install choke shaft lever on end of shaft on automatic choke side
- On altitude compensation models, place compensation choke valve link to both choke valves
NOTE: Lever and shaft are tapered. Attaching screw has LEFT HAND THREAD
- Install choke valve screws snug but not tight
- Close choke valve and tap lightly to align in housing
- Tighten attaching screws and stake (peen) screws in place
- If air valve shaft and plate were removed, insert shaft through holes on secondary side of air horn
NOTE: Slotted end of shaft must be in air valve spring chamber
- Install secondary metering rods into keyed slots in air valve plate
NOTE: Do not try to remove or install secondary air valve plate and metering rods with carburetor on vehicle. Shaft spacers, rods and screws can fall into intake manifold
- Install air valve plate into position. Guide metering rods into air valve wells
- Slide air valve shaft and spacer(s) in position
- Install air valve plate
- Close plate and tap to align in housing. Tighten and stake screws in place. Check for free shaft movement
- Install fuel inlet needle, seat and gasket
- Install auxiliary fuel inlet valve and gasket
- Install float and lever assembly and hinge pin
NOTE: Install hinge pin from accelerator pump plunger side
- Position return spring over air valve damper rod
- Install assembly through upper body
- Insert cranked end of damper rod into INNER arm hole on damper link
- Place damper link (bell crank) over post on air horn. Install split-pin shaft
- Place cranked end of air valve link through tang on air valve plate. Position other end through outboard end through remaining hole in damper link. Install "C" clip
- Insert pump bleed disc into pump bleed cavity
- Adjust float level at this time
- Mount mechanical bowl vent valve lever. Install retainer and screw
UPPER BODY-TO-MAIN BODY
- Install new air horn-to-main body gasket on main body
- Position upper body assembly over main body. Guide pump plunger and secondary throttle dashpot piston into their chambers
- Lower upper body onto main body. Install screws
- Position throttle levers so fast idle screw is on HIGH step of fast idle cam
- Insert key end of pump link into keyed hole in primary throttle lever
- Place threaded end of pump link through hole in pump lever
- Install nylon nut so that index marks made during disassembly line up
NOTE: Nut is self-locking
- Insert end of choke control rod into automatic choke lever. Install clip
- Install choke cover gasket
NOTE: Round hole in gasket must line up with air inlet hole in casting
- Install choke thermostatic spring housing and retainer
- Move cap to 90* RICH position
- Adjust fast idle cam clearance at this time
- Reset choke cap to correct position indicated in specifications
- Install carburetor on vehicle
- Adjust mechanical fuel bowl vent valve with carburetor on vehicle
