A Carter Thermo-Quad Guide

Copyright 1998 Gary Lewallen

Contents...

• Introduction
• History and Description
  • General
  • Identification
• Subsystems
• Port Diagram
• Choices and Adaptations
• Numeric Listing
  • Thermo-Quad
  • Rochester Quadrajet
• Modification of Subsystems
• References
• Acknowledgements

Introduction...

This guide is intended to provide information for identifying Thermo-Quad carburetors and related items. It provides a basic history and basic descriptions of the carburetor and its subsystems. It is not intended as a full theory of operation manual nor a repair manual. Service documentation should be consulted for repair procedures and service details. The factory service manuals provide good service procedures and theory for specific models. Other sources may be consulted for general repair and modification procedures as well as theory of operation. See the list of references for sources.

This guide is written with carburetor 'swapping' in mind. Thus, certain items are discussed with modification consideration (ie. emission subsystem disablement) with the intent for adapting a non-original carburetor and/or enhancing performance. The modification and adaptation of the carburetors may present legal issues, so consider the interest of any appropriate government(s).

History and Description...

General:

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 transducer 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. spreadbore, 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 environment, 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 vacuum (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.

Identification:

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'.

Subsystems...

Jets:

jets are contained in the primary 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 rods meter the fuel through the primary jets. They are essentially controlled by engine vacuum 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 inlet, 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 pump 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 transferred via a plastic tube internally to the squirter which resides above the primary venturi. Later models have two adjustment 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 throttle 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 arrangement similar to the AVS.

Choke:

OEM TQs use a divorced, manifold 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 are equipped with a compensator to allow extra 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. Used 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 'dieseling' 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 the 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 attached 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 (fender well) to signal the feedback solenoid controller to compensate.

Bowl Vent (BV) solenoid:

78-84. In an 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 vacuum 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. Used 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 trucks, 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 may 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 warm up.

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 function as the Throttle Position Solenoid. Also serves as a speed sensor.

Pulse Solenoid, Oxygen Feedback Control (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 models have a cover to prevent field adjustment of the pull-off.

Port 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 Vacuum Advance (black, 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", {located on phenolic float bowl}.
• (G) Bowl Vent (gold, 71-77), 11/32", ((located on the upper bowl cover}.
• (H) Air Cleaner Heated Air Temp Sensor (black, 78-84), 5/32".
• (I) Power Brake Tube (gold, 81-84), 111/32".
• (J) Air Cleaner Heated Air Temp Sensor (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 vacuum attachments were used, ie. secondary pull-off and vacuum throttle positioner...these (like item M) were external to the TQ.

Choices and Adaptations:

Choices:

There were several internal metering and passage changes that occurred 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.

The Competition Series carbs should generally be avoided except for racing. The aftermarket 9000 series were available in 4 models: 9801, 9811, 9800, and 9810. The 9801, 9811 have Chrysler linkage (9811 is EGR capable). Note: later OEM TQs model number started with 9 as well, not to be confused with the 9000 series. The 9801/9811 is the preferred aftermarket TQ.

Because TQs are out of production (since 1985), new parts are scarce except for common service items. Kits are available through Carter, Hygrade, KEM, etc. Floats, choke pull-offs, choke assemblies are also available. Tuning parts, ie. jets, rods, are no longer available new. Carter did make rod/jet kits ( Strip Kit ), but they are discontinued. Because replacement jets and rods are no longer available, tuning can be limited, unless a supply of used rods and jets is obtained. Many variations were used in the various applications over the years. Jets and rods can be modified. The carburetors are easy to rebuild. TQs usually work well with just normal service adjustments.

Adaptations:

TQ on 'squarebore' intake:

the TQ requires a spreadbore intake manifold. It can be adapted to a squarebore type via the use of an adaptor. Several companies make these (see Service Parts section). Some performance can be lost compared to a comparable spreadbore intake depending on the quality of the adaptor and the transition area. Vacuum leaks can be an issue too.

1-3/8" vs. 1-1/2":

The TQs have two different primary bore sizes. These units can be interchanged. The smaller bore will yield slightly better throttle response, but less overall flow.

Jets/rods:

The jets and metering rods's can be changed on the TQ to tune its performance. Many sizes were available. See the Service Parts section for sizing information. Many later model TQs were lean on the primary side. Increasing primary jet size and/or reducing metering rod size will richen the primary side. Secondary jets can be changed as well. If replacement units are not available, jets may be drilled to increase size. Rods may be filed to reduce size. Solder and drilling/filing can be used to reverse this to some extent.

Floats:

Early TQs had brass floats. By 1975, all TQs used nitrophyl floats. Over time, the nitrophyl floats can absorb gas and sink, allowing fuel levels to be too high. The floats should weigh 7.4-8.0 grams. Carter no longer services brass floats, but several sources are available (see the Service Parts Information section).

Accelerator pump clusters (squirters):

The accelerator pump clusters were available in various sizes. Drilling may be used to increase the orifices to tune pump fuel delivery.

Mixture screws:

the screws are readily accessible on 71-79 TQs. Some of these had plastic caps to limit travel. The caps can be removed. Some ~77-79 contained internal restrictors to mixture adjustment. These restrictions are in the base mixture path from the idle circuits and could be opened if needed. Note: mixture screws prior to 1976 had a 20 degree taper at the seat and cannot be interchanged with 77 and later 12 degree screws. 1980 and later TQs may have hidden screws. The base enclosed the screws in cast protrusions under press-in caps. The caps may be removed for mixture adjustment.

Interchanging bases, fuel bowls, upper bowl covers:

The three main TQ sections are matched for each applications. Most will interchange mechanically, but flow and metering characteristics may not match. The sections have casting numbers that will allow some interchange identity, but the casting machine work for applications may vary.

Evaporative Control System (ECS):

73 and later will have an extra base port for the charcoal canister purge. This is not a parasitic device and may be retained without decreasing performance. The bowl vent is plumbed to the canister to vent fumes. The purge pulls these fumes and those collected from the tank. The purge port can be capped to disable it.

Exhaust Gas Recirculation (EGR):

EGR occurs outside of the carburetor, but tuning and vacuum source provisions are incorporated into the various TQs used on EGR equipped vehicles. The tuning is usually not a major issue. TQs may provide a venturi or a front base port for EGR vacuum signals. If EGR is not used, these ports can be capped.

Idle Enrichment system (IE):

this system is a driveability enhancement. It allows a richer mixture during the warm up period to improve driveability. It supplements the choke function by blocking part of the air bleed to richen it. The TQ with IE will have 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. It is also integrated into the EGR delay circuit. The IE port can be retained or capped (if capped, the carb behaves normally).

Altitude Compensator (Alcomp...Alc):

This device alters the high speed metering circuit by sensing atmospheric pressure. It mounts to the same area as the IE system at the front of the bowl cover. This system is also a driveability enhancement, which also reduces emissions, by allowing the TQ to compensate for elevation. It could be disabled by blocking the air passage ports (or the front vent pipe) to allow a normal full rich condition for the high speed circuit.

Solenoid Bowl Vent (BV):

Most 1978 and later TQs have an electric bowl vent solenoid that replaces the earlier mechanical vent. 72-77 TQs used a linkage actuated bowl mounted vent that fed to the ECS charcoal canister. 71 TQs actuated the same way, but vented to the oil breather or the atmosphere. The later units vented through the rear base. The vent mechanism closes to vent to the ECS canister with the engine off. When started, engine vacuum opens the vent and the electric solenoid is powered to hold the vent open during low vacuum conditions. The electric power is supplied by the ignition run circuit. While running, or off-idle for earlier TQs, the bowls vent inside the air cleaner. Vents should be retained for all types. The solenoid bowl vent could be redesigned to eliminate the solenoid by adapting earlier parts, but the remachining effort is not worth the result. The solenoid bowl vent system can be retained by wiring into the ignition run circuit if adding to an earlier vehicle. If the ECS canister is not used the port can be vented to the atmosphere like 70 and earlier carburetors were done. A protective screen over the port can be used.

Oxygen Feedback Pulsing Solenoid (O2):

Most 1980 and later TQs will contain an oxygen feedback controlled, pulsed solenoid in place of an IE module. The solenoid is variably pulsed by the control computer based on the signal it receives from the exhaust mounted sensor. The solenoid alters the variable air bleeds by inputting more or less air based on computer signal duty cycle. If the solenoid is disconnected, the air bleeds will allow a full rich condition. Tuning with this in mind, this TQ could potentially be used in a non-control/feedback vehicle.

Idle Stop Solenoid (ISS):

the idle stop is external to the TQ and is used to prevent engine run-on. It can be retained, disconnected, or reused for other functions such as compensating for engine loading (ie. air conditioning) like a SIS unit.

Solenoid Idle Stop (SIS):

the idle stop is external to the TQ and is used to compensate for engine loading (ie. air conditioning). It can be removed if not needed.

Throttle Position Solenoid (TPS):

the solenoid is external to the TQ and is used for catalytic converter protection. It can be removed if not needed.

Vacuum Throttle Positioner (VTP):

the positioner is external to the TQ and is used for catalytic converter protection and/or a speed sensor. It can be removed if not needed.

Throttle Position Transducer (TPT):

the positioner is external to the TQ and is used to signal throttle position and movement rate to the computer. It can be removed if not needed.

Ground Switch:

the switch is externally to the TQ and is used to signal throttle closed to the computer. It can be removed if not needed for a computer or for idle adjustment.

Idle screw adjustment on ELB and ESA TTQs:

Lean Burn carburetor idle speed is controlled with the curb idle adjustment screw that contacts the "throttle closed switch contact". This contact signals the Spark Control Computer that the engine is at idle, or not. The contact is mounted on a bracket on the passenger side of the carburetor. There is also a transducer, but it is to sense throttle position and opening rate. Some had the conventional idle screw based on application. There are two approaches to the idle adjustment... 1) retain the "throttle closed switch contact" bracket (on the passenger side) and adjust the idle there...this was the factory curb idle adjustment. 2) Drill and tap the boss for the conventional idle screw. Drill the boss perpendicular and near the center, but align the hole with the throttle bracket extension. The factory screw size is 10-32. This approach yields an idle adjustment screw like earlier TQs had.

Adding vacuum advance port to ELB and ESA TQs:

Many Lean Burn carburetors lack a vacuum advance port because advance was controlled by the ELB computer. The port may be added to provide a vacuum advance signal for a conventional non-ELB/ESA distributor system. The vacuum advance port is somewhat tricky and is best performed by comparison to an earlier throttle base that has the factory port. Using ~5/32" drill bit, drill the throttle base where the vacuum port existed on previous units....drill into the open (roughly square) opening between the outside and the throttle bore. This will accommodate the vacuum fitting. Then, using ~1/16" drill bit, drill two holes just above the throttle plate into the same square opening from the throttle bore side one hole adjacent to the other parallel to the throttle plate. Then, using a knife or small screwdriver, blend the holes together into a slot. This serves as the off-idle transfer slot to feed the vacuum port. Press a short length of 5/32" pipe or an old fitting into the outside hole. Vacuum advance is now available. Using another base with the port as a guide will ensure proper placement of the transfer slot. Misplacing the vacuum idle transfer slot can cause an off-idle stumble and will necessitate additional tuning or replacement.

Tamper-proof choke pull-off:

TQs with this feature have a pull-off with the enclosure attached. These can be replaced with an earlier standard pull-off to allow choke tuning.

Fuel bowl inserts:

these may be removed to allow full bowl volume.

Other Considerations:

Main jet wells:

The primary jets in 772 and later TQs are screwed into a threaded insert in the fuel bowl bottom. This area is connected via a small plastic channel to the internal fuel pickup area. There is one channel for each jet. These channels are attached to the main body with an epoxy adhesive. The epoxy can weaken and begin leaking with age. Correction can be made by reattaching the wells with new epoxy (J-B Weld has been found to work). Remove the wells and the old epoxy. Clean the area and reattach the wells with a small bead of epoxy. Remove any surplus epoxy that may interfere with reassembly.

Bowl warpage:

Due to the phenolic material construction, the fuel bowl can warp. The area most prone to warpage is the upper edge corner of the bowl at the rear. Correction can be made by resurfacing the upper surface. A large flat file can be used to resurface for corner warpage or other irregularities. Warpage of the bottom (unlikely) may require replacement due to its configuration.

Bowl breakage:

Severe breakage may require replacement of the fuel bowl. Small breaks and cracks may be repaired with a fuel-resistant epoxy. The bottom surface has tabs for gasket location. If these break, repair is not required if the break does not extend into the bowl. Small breaks around the screw holes do not require repair if the break does not extend into other areas.

Idle transfer slot:

If the primary throttle plates are opened too far in an attempt to set the idle speed, the idle transfer slot may be exposed to the air flow. This can result in an off-idle hesitation. Correction can be made by drilling a 1/16"-1/8" hole in the forward half of each primary throttle plate. The holes allow sufficient air flow for speed setting without exposing the idle transfer slot.

Step-up piston spring:

The step-up piston spring resists vacuum pull on the piston. In cases where idle vacuum is too low to allow stable holding of the step-up piston, the spring may be trimmed to reduce its force.

Commercial rebuilders:

Carburetors that are mass rebuilt by commercial rebuilders have their useful service life shortened or ended. This usually stems from mixing parts, bad service procedures, and cleaning by tumbling or blasting. Tumbling and blasting removes the factory finishes. This leads to accelerated wear and corrosion problems. In the case of the TQ, the factory linkage was cadmium or irridite finished. The throttle shafts were Teflon coated. Tumbling or blasting removes these finishes and will lead to corroded sticking linkages and binding or leaky shafts. The TQ phenolic fuel bowl can be damaged by tumbling or blasting. Jets, rods and internal orifices are further damaged by these processes. Mixed parts without proper analysis can result in a poorly performing or useless unit. A carburetor from a rebuilder of this nature requires careful examination to determine its future usefulness.

Numeric Listing...

Listing Notes:

Known jet and metering rod information is included for the earlier years as this was documented by Carter and Chrysler. Later years were not documented as well. A kit reference number is given for each carb. The kits are referenced in the Service Information section. The Carter 'Zip Kit' is the primary reference. Some conflicts arise in the documentation. Carter information is used where conflicts occur.

All primary and secondary jets are prefixed with 120- for TQs. All metering rods are prefixed with 75- for 72 and later OEM and 9000 series. CS and 71 TQ rods are prefixed with 16-. The prefixes are omitted from the listing to save space.

The 'Kit' field contains a code corresponding to a row code under the carb kits in the Service Parts section. The code is referenced to the Carter rebuild kit or "Zip Kit". Some competitor kit numbers have been provided. These numbers have been cross-indexed to Carter's. The cross-index is not 100% due to some manufacturer variances. The most common cross-index has been chosen in these cases.

Note that most TQ model numbers had an 'S' suffix. Many will also appear with a 'TQ' prefix. These were left out of the list to save column space. Where known, Chrysler part numbers are also listed in parenthesis.

Because the Rochester Quadrajet replaced the Thermo-Quad in 1985, a brief listing of Quadrajets follows the TQs as reference.

Abbreviations:

AT

Automatic Transmission

MT

Manual Transmission ( No reference means both transmissions )

Pri.

Primary Jet

Sec.

Secondary Jet

Rod

Primary metering rod

Bore

Primary throttle plate diameter in inches, All secondaries are 2-1/4"

HP

High Performance

CA

California application; generic for CA, N95

F

Federal application ( No reference means both Federal and California.)

Can

Canada application. Typically, Canada used Federal carbs except noted.

LD

Light Duty

MD

Medium Duty

HD

Heavy Duty

LB

Lean Burn, ESA. Noted on 76's. After 76, most F cars were LB (N92, N94).

IE

Idle Enrichment

Alc

Altitude Compensator. Few noted, most CA and last years had Alc (N96).

HA

High Altitude

BV

Bowl Vent valve

O2

Oxygen feedback solenoid

Thermo-Quad Listing:

Rochester Quadrajet (M4ME & E4ME) Listing:

17085407	85-87 318 O2
17085408	86 360 Truck AT F (4306408)
17085409	86 360 Truck AT F HA (4306409)
17085411	85 318 Can Exp
17085411	86-87 318 (4306411)
17085414	85-88 360 Truck HD
17085415	85 360 Truck HD
17085416	85-88 360 Truck
17085417	86 360 Truck MT F (4306417)
17085425	86 360 Truck F (4306425)
17085431	86 360 Truck HD CA Can (4306431)
17085432	85-88 360 Truck HD
17085433	85-89 318 O2 (4306433)
17085434	86 360 Truck F (4306434)
17087175	85-88 360 Truck
17087176	85-88 360 Truck
17087177	85-88 360 Truck
17087245	85-88 360 Truck HD

Service Parts Information...

Metering Rod Info (dimensions in inches):

Rod #	Econ	Mid	Power	Notes
16-615	.059	--	.040	For CS only.
16-616	.064	--	.030	For CS only.
16-632	.057	--	.040	For CS only.
16-633	.055	--	.040	For CS only.
16-634	.062	--	.030	For CS only.
16-635	.060	--	.030	For CS only.
16-655	.062	--	.040	For 71 OEM TQ only.
16-683	.060	--	.035	For 71 OEM TQ only.
16-683	.058	--	.035	For 71 OEM TQ only.
75-1937	.070	.046	.040
75-1938	.071	.051	.040
75-1939	.070	.058	.040
75-1940	.072	.060	.045
75-1962	.067	.055	.045
75-1965	.069	.061	.045
75-1966	.067	.052	.045
75-1994	.068	.043	.035
75-1995	.066	.040	.035
75-1996	.069	.048	.035	*
75-1997	.067	.045	.035	*
75-1998	.070	.057	.040
75-1999	.068	.054	.040
75-2000	.066	.054	.035
75-2001	.064	.051	.035
75-2002	.065	.052	.040	*
75-2003	.063	.049	.040	*
75-2004	.067	.058	.040	*
75-2005	.065	.055	.040	*
75-2024	.066	.054	.040
75-2086	.069	.061	.040
75-2103	.069	--	.045
75-2109	.069	.061	.045
75-2110	.069	.053	.040
75-2144	.069	.061	.050
75-2145	.069	.061	.055
75-2153	.067	--	.055
75-2159	.070	.062	.040
75-2179	.074	.066	.042
75-2210	.069	--	.045
75-2211	.0715	.064	.040
75-2385	.069	--	.053

Primary Jet Info (dimensions in inches):

Jet #	Size
120-330	.077
120-331	.080
120-332	.083
120-333	.086
120-334	.089
120-335	.092
120-3074	.074
120-3077	.077
120-3080	.080
120-3083	.083
120-3086	.086
120-3089	.089
120-3092	.092
120-4092	.092 *
120-4095	.095 *
120-4097	.097
120-4098	.098 *
120-4099	.099
120-4100	.100 *
120-4101	.101 *
120-4104	.104 *

* denotes part of 10-203 Strip kit.

Secondary Jet Info (dimensions in inches):

Jet #	Size
120-339	.110
120-340	.113
120-341	.116
120-342	.119
120-343	.122
120-344	.125
120-3113	.113
120-3116	.116
120-3119	.119
120-3122	.122
120-3125	.125
120-3128	.128
120-3131	.131
120-5110	.110
120-5125	.125
120-5131	.131 *
120-5137	.137 *
120-5143	.143 *
120-5149	.149 *

* denotes part of 10-203 Strip kit.

Needle and Seat Info (dimensions in inches):

Accelerator Pump Cluster (squirter) Info (dimensions in inches):

Carb Kits (Zip Kits):

Carter Strip Kit:

Floats:

Chokes:

Carter 170-148. Chrysler 3512875:

4972,4973,6138,6139,6144

Carter 170-245:

6090,6140,6165,6166

Carter 170-1371. Chrysler 4287004. Hygrade CV400 (non-electric assist):

9379 (Canada)

Carter 170-1408. Chrysler 3698355,3751484,4027715,4027793,4095328. Hygrade CV164:

6318,6319,6320,6321,6322,6324,6339,6340,6341,6342,6410,6411,6456,6457,6459, 6460,6461,6462,6463,6503,9008,9009,9010,9011.9012,9014,9015,9016,9023,9024, 9046,9049,9050,9051,9052,9053,9054,9056,9057,9058,9059,9062,9063,9064,9065, 9066,9068,9069,9072,9073,9074,9077,9078,9080,9081,9094,9095,9097,9099,9100, 9101,9102,9103,9108,9112,9114,9116,9119,9127,9140,9149,9153,9182,9188,9190, 9221,9243,9251,9252,9254,9275,9279,9281,9288,9292,9296,9359,9370,9375,9376, 9379

Carter 170-1409 (non-electric assist):

6518,9000,9117,9118,9150,9151,9212,9214,9357,9358,9371

Carter 170-1490. Chrysler 4027792,4095984,3830548,4027714,4095341. Hygrade CV172,CV174:

6452,6453,6454,6455,6488,9002,9004,9055,9076,9093,9104,9115,9123,9124,9125, 9126,9134,9136,9137,9147,9152,9173,9183,9185,9187,9193,9194,9195,9196,9197, 9198,9202,9207,9208,9209,9210,9211,9215,9216,9217,9218,9223,9224,9225,9226, 9227,9228,9229,9245,9246,9250,9255,9256,9265,9266,9268,9269,9270,9271,9272, 9273,9276,9277,9278,9298,9299,9311,9314,9329,9330,9331,9332

Carter 170-1598 (non-electric assist):

9234,9236,9244,9305,9306,9320

Carter 170-1621. Chrysler 4095331. Hygrade CV241:

9325,9341,9342,9364,9365,9366,9367,9368,9369,9386,9389

Carter 170-1675:

9283,9284,9293,9364,9372,9374,9385,9388

Carter 170P-1322A:

9800,9801,9810,9811 (integral choke, 9000 series)

Also note: 73-up without electric assist: Chrysler 4027795, Hygrade CV370.

Choke Pull-offs:

Carter 202-742, 202-664 (71-up)
Chrysler 3621210, 4049239, 4049240, 4049275, 4131250 (71-up)
Hygrade CPA77 (71-up)
IHC 460369C1 (74-80)
Ford D4AZ-9J549a (74)
KEM CP146 (71-up)

Carter 202-818 (81-84 tamper-resistant)
Chrysler 4267133 (81-84 tamper-resistant)
Hygrade CPA276 (81-84 tamper-resistant)
KEM CP319 (81-84 tamper-resistant)

Carter 202-821 (81-84 secondary pull-off)
Chrysler 4267137 (81-84 secondary pull-off)
Hygrade CPA269 (81-84 secondary pull-off)
KEM CP320 (81-84 secondary pull-off)

Carter 202-981 (84 secondary pull-off, vacuum controlled)

Miscellaneous Parts:

O-ring, main well cavity:

Carter 163-90, Chrysler 3685655 (or 3549406)

Needle & Seat:

Chrysler 3621161, Carter 25-1086 (OEM size), Hygrade VN87C

Accelerator pump:

Chrysler 4094867, Carter 64-465

Spreadbore/squarebore adaptor:

MP P4007522, Edelbrock # 2691.

Air horn gasket:

Chrysler 53030600

1/4" spacer base gasket:

Chrysler 3698365

Set of four, 1/4" spacer base gasket (3698365):

MP P4007902

Solenoid Bowl Vent:

Carter: 213-93 (78), 213-145 (79-84 Truck, 79-80 CA), 213-211 (81 CA MT, Can, 81-84 Export), 213-111 (80-84 Mexico), 213-229 (CA AT Truck), 213-240 (81 CA late Truck) Pulsing Solenoid (O2):

213-193 (81-84 318 car)

Tools:

Air Valve Tool:

Carter 109P-397, Miller Special Tools # C-4152B

Strip Kits...

Early Kits, CS and other carbs:

Early Kits, OEM and 9000 TQ:

Later Kits, OEM and 9000 TQ:

Later Kits, AFB, AVS:

References...

• Carter Service Manual # 3623A "Thermo--Quad"
• Carter Service Manual # 3630A "Basic FF acts and Principles"
• Carter Carburetors catalog, # 3878, April 1975
• Carter Floats catalog 1980
• Carter Carburetor95 catalog, # 3788, August 1977
• Carter Zip Kits & Carburetor Components catalog, # 3880, 1991
• Carter Carburetor Emission Components catalog, # 3881, 1989
• Carter Performance Products catalogs 11979, 1980, 1982, 1984
• Carter Strip Kit Specifications & Instructions, # 3270, 1-73, revised 11-75
• Carter Strip Kit label, # 3272, 7-75
• "Carter Carburetors", SA-Designs, Dave Emanuel, 1983
• Chrysler Technical Guide, Thermo-Quad Carburetor, 1982, # 81-699-2009
• Chrysler Student Reference Book, Quadrajet Carburetor, 1984, # 81-699-5003
• Chrysler factory service manuals, various, 1971-1984
• Chrysler parts catalogs, various, 19711-1984
• Chrysler Technical Service Bulletin # 14-01-72C, Dec. 15 1971.
• Direct Connection & Mopar Performance catalogs
• Mopar Performance Engine Manual, # P52249010, 8th Edition
• Hot Rod magazine, June 1970
• Car Craft magazine, March 1972
• The Hot-Rodders Manual for Street & Strip, '79-'80 & '81-'82 Annual (Hot Cars)
• Popular Hot Prodding, October 1973, October 1981
• High Performance Mopar magazine, Summer 1988.
• Mopar Action magazine, February 1991, October 1991.
• Mopar Muscle magazine, August/September 1995.
• Chrysler Power magazine, January, March, May 1988.
• KEM Air & Fuel Management Systems Parts, # AF-114, 1993
• KEM All Line Buyers' Guide, # BG-116, 1995
• Hygrade Carburetor Kit & Component Parts Guide, # FC-91, 1991
• Hygrade Carburetor & Fuel System Parts Guide, # CM-88, 1988
• Hygrade Carburetion Component Guide, ## FT-91, 1991
• Holley Replacement Carburetors catalog, # L-30033-4, Spring 1985
• Borg Warner Carburetor Kits catalog, ## CK-79, Sept 1979
• Motorcraft Carburetor, Emission Parts & Tune-up Kits, # F200W, 1985
• AC-Delco Carburetors & TBI, Carb Kits & Parts, # 9A-100, 1986
• Tomco Remanufactured Carburetors & TBII catalog, # D.I. 1991, 1991
• Kimco Carburetors, # 30-9, 3-1-83
• Kimco Carburetor Numerical Listing & OEM Section, # 30-9, 3-1-83
• Mopar Mailing List (MML) postings
• My memory (not so good) and my Thermo--Quads (somewhat better).

Acknowledgements...

• Thanks to David Wright for early Strip Kit information.
• Thanks to Cam, Uncle Pete, Jim, and David for brass float information.
• Thanks to the MML in general.