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ThermoQuad 9103S ~ Worth Anything?

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  • ThermoQuad 9103S ~ Worth Anything?

    I have 2 of them, wondering if they're worth anything?

    bringin' em back ~ to the Dodge Mahal !!....

    Where old Magnums can find a home.. :angel:

  • #2
    It appears to be a 1977 400 application carb.
    The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.'
    Ronald Reagan


    • #3
      Are they cores, rebuilt, or unmounted?
      The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.'
      Ronald Reagan


      • #4
        If they are undamaged and unmolested, yes.....but I am not sure if they have a ported vacuum fitting or not; most people want a ported vacuum for the distributor advance. I am assuming that these are leanburn Fed emissions 400 carbs???

        Thermoquads rule....but some are better than others.....but MOST can be modified to perform well regardless! They might be one of the most maligned carbs, next to the Quadrajet.....but, if set up properly, they are superior to almost any OE carb out there! Like Ron Popeil says....."set it, and forget it!" LOL!

        I don't need them, since I have a pretty good collection of Tquads myself!


        • #5
          R-body and GS, they're used carbs that I uncovered while digging out other stuff.

          Someone educate me on how to identify LB vs. non-LB carbs?

          bringin' em back ~ to the Dodge Mahal !!....

          Where old Magnums can find a home.. :angel:


          • #6
            Originally posted by Magnumguy View Post
            R-body and GS, they're used carbs that I uncovered while digging out other stuff.

            Someone educate me on how to identify LB vs. non-LB carbs?

            If these carbs have a throttle position transducer on the right front, they are leanburn. However, there were some 400 HP? engines in '76-'77 that did not have leanburn, nor did they have cat converters.

            The best way to tell is by the carb number, and the likelihood of being delivered on a leanburn engine! If there is no ported vacuum fitting, they are leanburn, but the reverse may not be true!





            The Thermo-Quad (TQ) was initially released for competition in 1969. Chrysler introduced the TQ on the 1971 340. The first series of TQs including the 71 340 version and the Competition Series TQs were air metered units unlike like the 72 and later TQs which were solid (liquid) fuel metered. The Competition Series (CS) were available in 850 cfm and 1000 cfm ratings. CS units use a manual choke and have a minimal amount of external attachments compared to OEM production units. The CS was discontinued in the mid-70s. Carter released the 9000 series in the latter 70s as replacement carburetors for Chrysler and GM Quadrajet applications. The 9000 series was very similar to the production Chrysler Thermo-Quads.
            In 1972, the OEM Chrysler TQs changed to the solid fuel metering type. The TQ coverage was expanded to include the 400 engine. By 1973, all Chrysler 4-bbl applications were TQs (except some 413 truck models which continued to use a Holley carburetor). As the years progressed, the TQ evolved to meet the continually tightening emissions requirements. The changes were numerous. Many features were added or modified externally and internally. The late 70s contained many variations for the various geographic regions, the various features included/excluded, and the range of applications and engines produced. Into the 80s, the TQ became more complex, but year to year major variation lessened somewhat. In 1973, TQs received a port on the base for canister purge and a port on the main body to provide a venturi vacuum signal for EGR applications. 1975 saw the introduction of the Idle Enrichment system, Altitude Compensator on some models, and the Throttle Position Solenoid for the new catalytic converter equipped cars.
            In 1976, Chrysler introduced Lean Burn ignition and the TQ was modified to produce and run on a very lean air/fuel mixture. An external idle stop switch and throttle position tranducer were added. In 1978, the TQ bowl vent was modified with the addition of an electric Bowl Vent solenoid. An additional rear base port for the vent hose replaced the bowl vent port. The fuel inlet moved to the rear center of the carburetor from the previous rear side location. Lean Burn became Electronic Spark Advance (ESA) in 1979. The very lean mixture idea was abandoned, but the electronic control of the ignition advance was retained. Hidden mixture screws were a feature starting with some 1980 model TQs. 1981 introduced a riveted cover for the choke pull-off linkage to prevent tampering and the oxygen feedback solenoid on some models. Idle Enrichment and Altitude Compensator was not used on feedback models. 82-84 did not change much more in a major way. The canister purge was eliminated by 84 in some applications and a power brake port was added to the rear base.
            After 1984, Chrysler stopped using Thermo-Quads. Instead, the Rochester Quadrajet was used through 1989 on cars and until 1988 in trucks when Electronic Fuel Injection replaced them. Carter continued to supply the fuel pumps for the Quadrajet equipped vehicles. Although Chrysler was the primary manufacturer to use the TQ, International Harvester (IHC) used them in the late 70s and Ford used them in 1974.
            The Thermo-Quad was available with two primary throttle bore sizes, 1-3/8" and 1-1/2". Flow ratings (CFM) vary depending on the source, but the TQs with the 1-3/8" bores are listed as 750-800 CFM and those with the 1-1/2" primary throttle bores are rated at 800-850 CFM. All TQs have the 2-1/4" diameter secondary throttle plates. The primary bore size depended on application. In general, all 78 and later 318s and 360s and all 340s had the smaller bore. Earlier 360s varied depending on application, most 400s and all 440s had the large bore. The 9000 series have the small primary bore and were rated by Carter at 800 cfm. Later TQs (ie, Lean Burn and ESA applications, feedback systems) are quoted with less flow ratings, but this is due to the control of the carburetion system, not the inherent flow capability of the basic carburetor. The internal metering is set for leaner running conditions for Lean Burn. Either bore size can be tuned to run well on most engine combinations. The smaller bore offers a slight increase throttle response but less overall flow. The different bore sizing, ie. speadbore, is an aspect that can lead to increased fuel economy while delivering similar wide open throttle (WOT) performance to an equivalent standard bore configuration. The adjustability of the TQ and the spreadbore configuration allows the use of a large CFM carburetor on a small displacement engine.
            The TQ gets its name from the phenolic resin main body. This is "sand- wiched" between the aluminum bowl cover assembly and the lower throttle flange assembly. The plastic body keeps the fuel ~20 degrees cooler than an all metal carb in the same enviroment, leading to less percolation problems and increased performance due to a denser charge. The TQ is a metering rod based carburetor like other Carters (AFB, AVS, BBD). The primary jets are housed in the plastic body, the primary metering rods are suspended from the cover mounted step-up piston assembly into the jets (in the 71 TQ and the CS, the primary jets are also housed in the cover). Engine vaccuum (related to load) controls the position of the metering rod in the jet, metering the fuel flow. The secondary jets are suspended from the cover. Secondary flow is controlled by variable venturi effect in the secondary bores. The TQ secondary throttle plates are controlled by direct mechanical linkage, air flow is controlled by a secondary, spring tension resisted, air valve. The valve is further controlled and damped by the choke pull-off diaphragm.
            The OEM TQs have a divorced choke (73-up with electric assist in most applications), the 9000 series have an integral electric choke, and the CS were equipped with a manual choke. All OEM TQs and later CS have screw-in jets. Early CS retained the jets via O-rings.

            To identify TQs, the model number is stamped on the lower left rear bolt flange. Earlier TQs also had a tag under one of the front bowl cover screws, later ones have a bar code sticker on the bowl cover with the Carter model and/or a Chrysler part number. International Harvester TQs also have a tag under a front bowl cover screw.
            Additional numbers will be found on the carburetor sections. These numbers are not used for TQ identification, but some can be used to relate one casting to the other (note that parts with the same casting number may be machined differently). The upper bowl cover has the casting number on the top, right of center rear: 6-XXXX (example: 6-2141, 6-2080, 6-2024). The bowl has the casting number molded on the bottom of the right bowl near the front, it is difficult to see with the throttle base on the carb: 0-XXXX (example: 0-2511A, 0-1823, 0-2709A). The throttle base has the casting number on the right upper side in a small recess: 1-XXXX (example: 1-2357, 1-2294, 1-2967. More numbers will be found ink stamped, cast or stamped in various areas. Moreover, numbers are usually stamped below the model number on the lower left rear bolt flange. The model number consists of four digits, usually followed by an 'S' (ie. 6318S). The model number is the primary and documented identifier.
            The 71 OEM units can be identified externally by the mixture screws which protrude at an angle from the base, in the same plane as the base, later units protrude perpendicular to the base plane, but angle upwards from it. Note: some 1980 and later units have hidden mixture screws. The Competition Series have raised pads on the upper bowl cover for a label. Also, the CS have minimal external attachments, such as the lack of a PCV port. The mixture screws are similar to the 71 OEM TQs.
            The fuel inlet on the CS and the 78-84 OEM units was located in the rear center and the 71-77 OEM and 9000 series have the fuel inlet on the right rear side. The aftermarket 9000 series were available in 4 models: 9801, 9811, 9800, 9810. The 9801, 9811 have Chrysler linkage (9801/9811 is EGR capable). Note: later OEM TQs model number started with a 9 as well, but are not to be confused with the aftermarket 9000 series.
            TQs with 1-3/8" primary throttle bore will have '2-315' stamped on the throttle plates. 1-1/2" units will have '2-314' stamped on the plates. All secondary plates are stamped with '2-312'.

            This section briefly describes the primary Thermo-Quad subsystems that are readily accessible and the various attachments for emissions. For detailed theory of operation of the subsystems or general operating functions such as the low and high speed metering circuits, refer to the references listed in the References section, specifically the Carter Thermo-Quad service manual. See the Service Parts Information section for details on parts and part numbers.
            Jets: jets are contained in the primaary and secondary circuits, one for each barrel. Early CS units had press-in jets retained by o-rings. CS and 71 TQs have the primary jets in the upper bowl cover. All other TQs have screw-in primary jets in the main body. All TQs have the secondary jets mounted in the upper bowl cover. All jets have a part number prefix of 120-. 72 and later TQs usually have the part suffix stamped on the jet, primaries: 4XXX, secondaries: 5XXX (or 120-5XXX). The XXX denotes the size, example: 4098 = 0.098", 5137 = 0.137". CS and 71 TQs have part number suffixes of 3XX or 3XXX.
            Metering rods and step-up: metering rrods meter the fuel through the primary jets. They are essentially controlled by engine vaccuum and a mechanical link, step-up cam/lever, connected to the primary throttle shaft. Many variations of metering rods were available through the years. The depth of pre-76 models could be adjusted to tune, ( primarily ), cruising condition flow via a screw adjustment. Some later models retained this feature, but starting in 1980 may have the adjustment locked via a collar. Metering rods have three steps for metering, economy, midrange, power. They are usually stamped with a part number, 75-XXXX or XXXX where the XXXX defines the step sizes. The CS and 71 TQs have numbers 16-XXX.
            Floats: TQs are a single fed, dual innlet, dual bowl carburetor. One bowl feeds each carb half, ie. one primary and one secondary. The dual bowl arrangement is contained in the phenolic main body. Dual floats and dual inlet valves are employed. Early TQs used brass floats. Later models (73-74 and later) use nitrophyl floats. All OEM TQs are equipped with needle & seat number 25-1086 (0.0935" orifice).
            Accelerator pump: the accelerator pummp is located on the left front and feeds from the left fuel bowl. The pump is activated by the left side throttle bracket. There is some stroke adjustability at the upper lever. The fuel is transfered via a plastic tube internally to the squirter which resides above the primary venturi. Later models have two adjusment holes instead of three, and perform a two stage pump that add additional fuel as the secondaries open. Three accelerator pump clusters (squirters) were available.
            Secondary air valve: TQ secondary thrrottle plates are mechanically linked to the primary on the left side. As the plates begin to open, the secondary air valve senses the opening and begins to open to provide air flow which starts fuel flow from the secondary jets. The initial opening and rate is determined by a counteracting tension spring inside the cover. The opening is additionally regulated and dampened by the choke pull-off assembly. The air valve is contoured and the movement provides a variable venturi effect. A secondary fixed baffle is mounted below the air valve. Total air valve movement is limited by a protruding tab. The counteracting spring tension is adjustable via a slot/lock screw on the left side to tune the rate. Carter designed a special tool to facilitate this adjustment. Some of the CS TQs used an adjustment and lock screw arangement similar to the AVS.
            Choke: OEM TQs use a divorced, manifoold mounted choke. Exhaust crossover heat operates the thermostatic spring contained in the choke well. Most 73-84 TQs were electrically assist heated. The electric control is via a small module mounted to the intake or right head. This unit times the assist based on temperature and time and receives power from the ignition run circuit. 9000 series have an integral choke assembly identified by the black, circular plastic thermostat housing. This unit is electrically controlled. CS units have a manual choke. Choke action is accomplished via the choke plate in the top of the primary side.
            Mixture screws: screws used through 11976 had a 20 degree taper at the seat. In 1977, this was changed to 12 degrees to reduce adjustment sensitivity. Some ~77-79 TQs also contained internal restrictors to limit adjustment. Plastic caps with tabs to limit adjustment were also installed on several models. Many 1980 and later TQs had the base redesigned to enclose the mixture screws so they could be 'capped' via plugs after factory setting.
            Choke pull-off: All TQ models. This performs the vacuum kick pull-off function for the choke at initial cold engine start. It is also used to regulate and dampen secondary air valve opening. Mounted on the right rear base under a mounting bolt and screw. Connects to the rear vacuum port, right, color code gold. The CS has the diaphragm for secondary air valve control only.
            Hot Idle Compensator: Some models aree equipped with a compensator to allow exta air into the mixture during high heat conditions. If equipped, it is located on the bowl cover over the secondary air valve. High temperatures can create an over-rich idle condition, and this compensates for it, by allow extra air flow when it opens.
            Idle Stop Solenoid (ISS): 71-76. Useed to set the idle higher than the basic curb idle screw for emissions reduction and to allow further closure of the throttle blades at engine shutdown to prevent 'deiseling' or 'run-on'. Mounts on a bracket retained by base mounting bolt and screw on the right side for 72-76. 71 mounted to the left side of the intake under the carb linkage.
            Exhaust Gas Recirculation (EGR) port: 73-84, not used in some 76~81. Some located on the main phenolic body as a tap into the venturi for vacuum signal. Venturi port is connected to a vacuum amplifier if used. Some models use a ported signal via a base port on the right front. Base ports color coded black. Venturi ports are brass.
            Evaporative Control System (ECS) port: 73-84. Used to purge the ECS charcoal canister of collected gas fumes from the bowl vent and fuel tank vent. Color coded red.
            Idle Enrichment (IE) system: 75-81. This is a driveability enhancement. It supplements th choke function by allowing an even richer mixture during the warm up period to improve driveability. This will appear as a small attachment on the front bowl cover that has a vacuum port that connects to a coolant temperature sensor (CCIE), then to manifold vacuum with bleed. It will also be plumbed into the EGR delay timing system.
            Altitude Compensator or Alcomp (Alc): 75-81. This is another driveability enhancement. It appeared on most California and Federal high altitude cars. It appears as a small cylinder attaced to the front of the Idle Enrichment system at the front of the bowl cover. A small bellows inside reacts to altitude changes and alters the air flow in the high speed metering circuit. This improves driveability and reduces emissions by maintaining a correct fuel/air mixture. Note: later vehicles may be equipped with a remote Alcomp sensor (fenderwell) to signal the feedback solenoid controller to compensate.
            Bowl Vent (BV) solenoid: 78-84. In aan effort to completely capture all fuel bowl evaporative emissions, the standard bowl vent was redesigned with a two way valve and holding solenoid at the rear of the carburetor. When the engine starts, manifold vacuum pulls the valve rubber 'puck' down, opening the bowl to the canister port. The solenoid is connected to the ignition run circuit and holds the valve open during low vaccuum periods while running. When the engine is shutdown, the valve releases and reseals the float bowl. Connects to rear base port, color code gold.
            Ground Switch: 76-84. This appeared with Lean Burn (LB). It signals the computer that the throttle plates are at idle position. Later models with solenoid idle stop combined the functions. It is located on the bracket on the right front. A throttle shaft attachment contacts it.
            Throttle Position Transducer (TPT): 776-81. This appeared with Lean Burn. It signals the position and movement rate of the throttle to the computer. It is attached via the same bracket as the Ground Switch.
            Solenoid Idle Stop (SIS): 81-84. Useed to set the idle higher than the basic curb idle when additional heavy accessory load (ie. rear window defogger, air conditioning) is placed on the engine. Mounts on a bracket on the right front.
            Dashpot: Some models, primarily truckks, may have a dashpot to slow throttle closing rate to reduce stalling. Mounted on a bracket on the left front.
            Vacuum Pull-Off Choke: A few models mmay have an additional pull-off mounted on the left rear. This connects to manifold vacuum via a control switch in the vacuum plumbing. It prevents choke operation after engine warmup.
            Throttle Position Solenoid (TPS): 75--later, some models. Mounts in the same place as the idle solenoids and is used to delay full throttle closure at deceleration to prevent a momentary rich condition thus protecting the catalytic converter(s).
            Vacuum Throttle Positioner (VTP): 75--later, some models. Mounts in the same place and performs the same funcion as the Throttle Position Solenoid. Also serves as a speed sensor.
            Pulse Solenoid, Oxygen Feedback Controol (O2): 81-84. Mounts on the front of the bowl cover (where the IE module mounted earlier). This solenoid is used to control the air/fuel mixture via varying duty cycle pulsing from the control computer based on feedback from exhaust, engine, and ambient sensors.
            Fuel bowl inserts: some later models had an insert in the fuel bowls to reduce the bowl fuel volume.
            Choke pull-off cover: many 81-84 modeels have a cover to prevent field adjustment of the pull-off.
            Port Diagram

            This section contains a diagram and notes to identify the various hose port connections on the Thermo-Quad. Different port configurations were used throughout the years. The diagram is a representation of the throttle base, top view. It is drawn with all possible ports. The label notes identify the ports and their general usage. Some ports are contained in the bowl or bowl cover. These are also identified. The ports are labeled by (x)...descriptions follow the diagram.

            FRONT ----- ___ _ (B) | | | | || || | | | | || //(F) || || | | | | || // -------||-------|---|---|-|----||------ | O (A) (C)* (D) (E) O | /| | | / |(G) | | / | | ----- ----- |--- / | / \ / \ | / | | | | | |--- =| |=O===O=| |=O===O=| |= | | | | | | | \ / \ / | | ----- ----- | | ----------- ----------- | | / \ / \ | | | | | | | | | | | | | =| |===O=====O===| |===O=====O===| | | | | | | | | | | | | | | \ / \ / | | ----------- ----------- | | | | | | | | O (H) (I) (J) (K) (L) O | ---||--|---|-||--|---|---||------------ ------- || | | || | | || \ / || | | || | | || ----- / / | | // / / | | (M) / / | | --- | | --- REAR ----
            • (A) Distributor Vaccuum Advance (blackk, 71-75, some 76-84), 5/32".
            • (B) Idle Enrichment (IE) (gold, 75-81 some models), 5/32".
            • (C) PCV (gold, 71-84), 11/32". * Note:: angled on 80-84 models.
            • (D) Canister Purge (ECS) (red, 73-82),, 1/4".
            • (E) EGR (gold) or Air Pump (blue), 5/332".
            • (F) EGR venturi port (brass), 1/8", {llocated on phenolic float bowl}.
            • (G) Bowl Vent (gold, 71-77), 11/32", ((located on the upper bowl cover}.
            • (H) Air Cleaner Heated Air Temp Sensorr (black, 78-84), 5/32".
            • (I) Power Brake Tube (gold, 81-84), 111/32".
            • (J) Air Cleaner Heated Air Temp Sensorr (black 71-77), 5/32", Bowl Vent Solenoid Vacuum Tube (gold 78-84), 5/32".
            • (K) Canister Bowl Vent Tube (gold, 78--84), 11/32".
            • (L) Choke Pull-off (gold, 71-84), 5/322".
            • (M) Choke Pull-off Diaphragm (natural,, 71-84), 5/32", {bolts to TQ base}
            • some other vaccuum attachements were uused, ie. secondary pull-off and vacuum throttle positioner...these (like item M) were external to the TQ.
            Choices and Adaptations:


            Chrysler used the TQ from 1971-1984. Ford used it in 1974 on some 460s and International Harvester used it in 74, 75, 79, 80 on 345/392 engines. The CS series was available from 69-~73. The aftermarket 9000 series was available from ~76-~late 80s. The best OEM years to locate are 72-75. TQs from this period have the least emission control add-ons. The 71 OEM TQ performs well and has minimal emission considerations. Due to its air metered design, it is unlike the later TQs and few parts are still available for it. The CS TQ was not intended for street use, thus it lacks provisions for many street engine items. Carter released the 9000 series in the latter 70s. It is a good unit for most applications. It is the same design as the OEM TQ with minimal emissions devices. In 76, Chrysler introduced Lean Burn (ELB) which evolved into Electronic Spark Advance (ESA). The 76-80 carburetors can be adapted for use in earlier vehicles. Many will need idle screws and vacuum ports added. Most 78 and later TQs use a more complex bowl venting arrangement. The IHC carburetors are fairly simple like pre-76 Chrysler TQs. 1980 TQs began began receiving a pulsing solenoid as part of an oxygen sensor feedback system to allow more computer control of the mixture. The TQs from this period are the most complex and least desirable units.
            There were several internal metering and passage changes that occured over the years for emissions. Most TQs can be tuned to match most applications. The later carbs, however, will need extra adaptation for earlier vehicles.


            Sorry, the diagram did not copy and paste well! LOL!

            Last edited by R-body_mopar; 03-01-2009, 08:54 PM. Reason: no diagram.....LOL! Duh!


            • #7
              I googled the same list that R-Body gave you to get the info that I left.
              I just asked the pointed questions so others knew what you had.
              The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.'
              Ronald Reagan