Evidently the factory Thermo-Quad equipped 1973 340 (intake manifold casting #3671918) used a thermostatic choke along with an electric wire that attached to a solid state "controller" that assisted in opening the choke a little quicker than from crossover heat alone. Common knowledge/experience has found the factory controllers burn out in no time and are not available in the aftermarket anyway. I'm sure there must be some clever forum members that have found a viable solution to fix the choke problem using their common sense (I even wonder if a manual choke has ever been adapted to a Thermo-Quad?). Thank you for any tips that can help when I install the 340 with above intake manifold and Carter 6319S carb on my '72 SSP. (before and after photos)
Most of the divorced, manifold mounted choke thermostats on 1973-1984 Thermo-Quads were electrically assist heated. The electric control of the choke heater is via the small module mounted to the intake or right head. This unit times the assist based on ambient temperature and run time. The unit receives power from the ignition run circuit and applies voltage to the choke thermostat electric assist. Four styles of electric control units performing a similar function were used depending on application:
- 1973-1976 single stage. Chrysler part numbers: 3656730, 3698357.
- 1974-1976 dual stage. Chrysler part numbers 3755750, 3755770, Auto-Tune # A32-901.
- 1977-1984 single stage. Chrysler part number 4049799.
- 1977-1984 dual stage. Chrysler part numbers 4049777, 4091034, Auto-Tune # A32-903.
The dual stage units have an additional external resistor compared to the single stage units. 3656730 or 3698357 is the original number for a 1973 340, but the later units will also function. The control units are not readily available in the aftermarket, but the units rarely fail in normal operation. My 1973 Duster, 1974 D200, 1977 Fury, and 1979 Newport all still have their original units with mileage ranging from 253000 to 380000 miles.
Part numbers for the choke for a 1973 340 using a 6319S Thermo-Quad are as follows:
- Carter 170-1408.
- Chrysler 3698355, 3751484, 4027715, 4027793, 4095328, 4095331, 4095341, 4095984.
- Hygrade CV164.
- Tomco 9076.
- Auto-Tune A32-226.
- Borg Warner TH-169.
- Filko 31-92.
- P&D E20.
- Walker 102-1003.
Other chokes on later model Thermo-Quads can also be used. A non electric assist choke was available in some applications that can be used to replace the electric assist choke under the following numbers:
- Carter 170-1409.
- Chrysler 4027795, 4186322.
- Hygrade CV370.
- Auto-Tune A32-188.
- Tomco 9190.
- Filko 31-290.
- Walker 102-1077.
And the following from a Canadian application:
- Carter 170-1371.
- Chrysler 4287004.
- Filko 31-275.
- Hygrade CV400.
- Walker 102-1014.
I haven't used it, but Mike's Carburetor Parts does produce a conversion kit for the Thermo-Quad and other carburetors:
Thermo-Quad Electric Choke Conversion Kit
This kit replaces the factory divorced choke and relies on the 1973 and later factory Chrysler Choke Electric Control for its connection and control. It does not mount to the carburetor itself like those on the 9800 series Super-Quads or the Ford Thermo-Quads.
Some numbers for the thick base gaskets plus some other gaskets and spacers are listed in the following:
- 5/16" base gasket (open): Chrysler 3698365, 3879786, 3751286, Fel-Pro 1902, 60273, McCord 66-0144, Victor-Reinz G14589 (G26662 for 1971-1972), Rol CM55011 (CM55256 for 1971-1972), Walker G897, Mahle/Clevite G14589, Borg Warner 14279.
- Base gasket (4-hole): Mr. Gasket 57A, Trans-Dapt 2072.
- 1/4" spacer base gasket: Fel-Pro 60038.
- Set of four, spacer base gasket (3698365): Mopar Performance P4007902.
- 1971 340 base gasket/spacer: 3512869 (asbestos gasket), 3512870 (aluminum spacer).
For more Thermo-Quad information, visit:
Vaanth Thermo-Quad Guide Site.
