TQ mechanical choke

[Furydude1960]

I bought a 71 fury with 440 and Thermo quad… I haven’t taken delivery yet, but it should be here within two weeks.
It was fully restored about 6500 miles ago, but since the owner died in 2022, it’s driven only a few times a year.
I saw two videos of cold starts, where after setting the mechanical choke, the seller had to flutter the throttle to get it to start. But once started, it ran with no problem….. idle seems normal.
I plan on siphoning out most of the gas, and add new. But I have three questions:
1: should I use a carb cleaner additive?
2: are there known issues with the mechanical choke system that I should be aware of?
3: where can I source a good service and troubleshooting manual on the TQ?
Many thanks,
JB

 

[CBODY67]

Some outstanding TQuad manuals were recently in posts by @Vaanth in here.

As to the choke operation, does it stay closed too long OR does it come off too quickly? Important differences! If, as the engine starts, the choke pull-off diaphram should pull the choke open slightly so the engine does not choke-down from being too rich, initially. IF the choke opens slowly and might need some nudging to get the choke further open, that can be the choke thermostat being adjusted a bit too rich and needing ADJUSTMENT a notch leaner. It might also mean the linkages just need a bit of lube sprayed on them, too.

Usually, the basic choke thermostat (in the intake manifold) can be adjusted and do not break. The vac diaphrams can leak with age, though, and that might be a more normal part to need replacement. All of the diaphrams are unique to the type of carburetor, though.

@Vaanth might have some other suggestions as to parts availability?

Just some thoughts,
CBODY67

 

[Big_John]

1: should I use a carb cleaner additive?
2: are there known issues with the mechanical choke system that I should be aware of?
3: where can I source a good service and troubleshooting manual on the TQ?

1. I wouldn't.
2. Not really. The choke pull off has a rubber diaphragm that may fail with age, but easy to check and replace.
3. Service Manuals – MyMopar for a service manual.

I plan on siphoning out most of the gas, and add new.

Do this BEFORE touching anything on the carb or choke. Then drive it. If the car is running now with old gas, it's going to run better with fresh gas.

The cold starts may also be a matter of getting gas to the carb if it's been sitting for a while too. Don't go ripping into the carb (or anything else) until you have driven the car.

One thing to remember too is most carb problems are actually ignition problems.

 

[Vaanth]

I bought a 71 fury with 440 and Thermo quad… I haven’t taken delivery yet, but it should be here within two weeks.
It was fully restored about 6500 miles ago, but since the owner died in 2022, it’s driven only a few times a year.
I saw two videos of cold starts, where after setting the mechanical choke, the seller had to flutter the throttle to get it to start. But once started, it ran with no problem….. idle seems normal.
I plan on siphoning out most of the gas, and add new. But I have three questions:
1: should I use a carb cleaner additive?
2: are there known issues with the mechanical choke system that I should be aware of?
3: where can I source a good service and troubleshooting manual on the TQ?
Many thanks,
JB

The Thermo-Quad was not available on the 440 until 1973, so your 1971 440 has been refitted with an intake manifold and carburetor.

The previous posts have provided good input, but to add a little to that for your questions:

1. After replacing the old gas in the tank, preferably with non-ethanol gas if available to you, a cleaner additive is not necessary, but adding Berryman B-12 Chemtool to a full tank initially, and on occasion, can be helpful.

2. Factory Thermo-Quad 440 intake manifolds have the provision for a divorced choke, and except some truck, marine, or industrial engines, the choke has an electric heat assist with an external controller. A non-electric assist was available on some non-passenger car applications. Known issues can be maladjustment, incorrect linkage, weak thermostatic spring, or damaged or sticking choke pull-off. The vacuum controlled choke pull-off can be checked with a vacuum pump, or simply depressing the diaphragm and blocking the vacuum port to see if it holds vacuum and releases smoothly. From your description of the start-up, it does not necessarily sound bad, just a cold start after sitting with possible gas loss due to evaporation or draining. Adjustment might be needed, but as advised, don't make any changes until you get the car in person, inspect everything and get known good gas in it.

3. Chrysler's own service manual for the year and application of the Thermo-Quad is the best in general. To identify the original application of the carburetor, see A Carter Thermo-Quad Guide. The guide is an information and reference tool for identification, parts information, some theory, and some adaptations. Some general service, theory information, and other can be found in the Other section of my site.

Although a rebuild is not indicated, if you get to that point, in addition to the factory service manual, the rebuild kit instructions are usually good, and some rebuild tips can be found in this post.