ThermoQuad info

FRONT
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(B) | | | |
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| O (A) (C)* (D) (E) O | /|
| | / |(G)
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| ----- ----- |--- /
| / \ / \ | /
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=| |=O===O=| |=O===O=| |=
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| \ / \ / |
| ----- ----- |
| ----------- ----------- |
| / \ / \ |
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=| |===O=====O===| |===O=====O===| |
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| \ / \ / |
| ----------- ----------- |
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| O (H) (I) (J) (K) (L) O |
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/ / | | //
/ / | | (M)
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REAR
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- (A) Distributor Vaccuum Advance (blackk,, 71-75, some 76-84), 5/32".
- (B) Idle Enrichment (IE) (gold, 75-81 ssome 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), 5/3322".
- (F) EGR venturi port (brass), 1/8", {lloocated on phenolic float bowl}.
- (G) Bowl Vent (gold, 71-77), 11/32", ((llocated 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--884), 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 uussed, ie. secondary pull-off and
vacuum throttle positioner...these (like item M) were external to the TQ.

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Choices and Adaptations:
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Choices:
- - - -
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.

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 prefered 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:
- - - - - -
Note: for tuning basics and repair procedures see the References section
for possible information sources. This section considers basic and
emission subsystem adaptation possibilities.


- TQ on 'squarebore' intake: the TQ reqquuires 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. Vaccuum leaks can be an issue too.

- 1-3/8" vs. 1-1/2": The TQs have two ddiifferent 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 rodss 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. BBy 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 readillyy 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, upperr 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 aand 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 ooccurs outside of the carburetor, but
tuning and vaccuum 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 vaccuum signals. If
EGR is not used, these ports can be capped.

- Idle Enrichment system (IE): this syssttem is a drivability 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): TThis 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 drivability 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 anndd 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 vaccuum 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 inputing 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 sttoop 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 sttoop 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): thee solenoid is external to the TQ and is
used for catalytic converter protection. It can be removed if not needed.

- Vacuum Throttle Positioner (VTP): thee 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): hhee 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 externall 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 TTQQs:
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 vaccuum advance port to ELB andd ESA TQs:
Many Lean Burn carburetors lack a vaccuum advance port because advance was
controlled by the ELB computer. The port may be added to provide a
vaccuum 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 accomodate 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 lenght 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 necesitate additional tuning or replacement.

- Tamper-proof choke pull-off: TQs withh 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 removveed to allow full bowl volume.