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1973 340 Choke Thermostat #966073
04/04/11 08:24 PM
04/04/11 08:24 PM
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Atlanta Indiana
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Dave Watt Offline OP
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I'm looking to purchase a choke thermostat for a '73 340 Thermoquad. No idea what it should look like. I've been online to NAPA, Advance, and O'Reilly. Auto Zone seems to have the only one that is labled correctly, most will show a 340 2BBL application. This is a Duralast manufactured by Wells. Does this look correct?
Web pagehttp://www.autozone.com/autozone/parts/D...56_207659_8298_

Last edited by Dave Watt; 04/04/11 08:30 PM.
Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966074
04/04/11 08:52 PM
04/04/11 08:52 PM
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Valencia, España
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thats the one my BB 4bbls have and I think SBs are the same

connects to this:


welll actually thats double stage for BB... the SB uses single stage which are the same but without the ballast


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: 1973 340 Choke Thermostat [Re: NachoRT74] #966075
04/04/11 09:30 PM
04/04/11 09:30 PM
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Where in the world does that thing go and what is it? I've had my car for 26 years, learn something new every day.

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966076
04/04/11 09:54 PM
04/04/11 09:54 PM
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Shoreline, Washington
72roadrunnergtx Offline
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Here's some detailed info on choke heater controls


1972 Road Runner GTX 440 6bbl 5-speed
[img]http://72rrgtx.com/carpics/bucket/DSC06730r-1.jpg[/img]
Re: 1973 340 Choke Thermostat [Re: 72roadrunnergtx] #966077
04/04/11 11:22 PM
04/04/11 11:22 PM
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Very interesting read. You've really done some intense work to get it right. Thanks for sharing with us.

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966078
04/05/11 12:01 AM
04/05/11 12:01 AM
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is not REEAAALLY NEEDED OR MANDATORY due engine heats by itself the coil, but is an electrical assistant to shorten the choking time and really helps out.

the units with ballast sends two diff voltage sets what changes with engine bay temperature. ( double stage )

The units without that, has only one voltage level untill warms up ( single stage )

normally SB and /6 carries single stages


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: 1973 340 Choke Thermostat [Re: NachoRT74] #966079
04/05/11 10:07 AM
04/05/11 10:07 AM
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Actually, I think your information will help an engine with the heat crossover blocked off.
Thanks again.

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966080
04/05/11 10:08 AM
04/05/11 10:08 AM
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So is the part in my above photo the correct part for a '73 340?

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966081
04/05/11 12:10 PM
04/05/11 12:10 PM
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Iowa
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NO it's not...at least it's not for a 318 application.

My 73 318 uses two bolts to hold it to the intake. All the replacements I've found use one bolt and one tab like in your picture.

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966082
04/05/11 04:42 PM
04/05/11 04:42 PM
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73’ was the first year electrically heated choke springs were used for most engine carburetor combinations. The intent was to get the choke off quicker than engine heat alone could for the sake of meeting emission requirements of the day. If the choke spring pictured is correct for your application, the pic clearly shows it having a heating element, then a choke control was installed on your car originally (usually under a intake manifold bolt head, on the passenger side near the choke well). Unlike modern day aftermarket electric chokes, those heating elements draw close to 2 amps while in operation and was only required during the first 5-10 minutes of cold start, after which crossover heat keeps the spring relaxed. 2 amps added to the ignition run circuit, including the bulkhead connector and ignition switch. As mentioned, there were a couple different versions, with and without a by-pass resistor, and was later superseded to a solid state design around 77’ or so and continued on through to the end of carbureted engines.
I believe Nacho’s point was if you go without the controller (don’t power up the heating element and crossover is open) there will be sufficient heat to open the choke, just later than originally designed.


1972 Road Runner GTX 440 6bbl 5-speed
[img]http://72rrgtx.com/carpics/bucket/DSC06730r-1.jpg[/img]
Re: 1973 340 Choke Thermostat [Re: 72roadrunnergtx] #966083
04/05/11 04:55 PM
04/05/11 04:55 PM
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The choke control was mounted to the front coil bracket bolt. I've been looking for origonal pictures of 73 340's. I havn't found one yet that clearly shows the thermostat. Other than the number of mounting bolts, the one pictured is right.

I did find a picture of a survivor 74 Cuda with a 318 and it has the mounting arangement like the one you pictured. It just uses a straight rod instead of an angled one like the 4-barrels had. The 73 318's may have used an oddball thermostate.

Re: 1973 340 Choke Thermostat [Re: NachoRT74] #966084
04/05/11 05:07 PM
04/05/11 05:07 PM
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Cincinnati, Ohio
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Quote:

thats the one my BB 4bbls have and I think SBs are the same

connects to this:


welll actually thats double stage for BB... the SB uses single stage which are the same but without the ballast




Are those available in the aftermarket? I'm thinking so. I have a few stock iron manifolds with those things still attached.

Re: 1973 340 Choke Thermostat [Re: Challenger 1] #966085
04/05/11 05:16 PM
04/05/11 05:16 PM
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St. John's Newfoundland
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Quote:



Are those available in the aftermarket? I'm thinking so. I have a few stock iron manifolds with those things still attached.




You can get a modern equivalent that works the same, but they don't look like originals.

6570040-92738.jpg (697 downloads)
Re: 1973 340 Choke Thermostat [Re: Challenger 1] #966086
04/05/11 05:17 PM
04/05/11 05:17 PM
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Conway, SC
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The picture the OP posted does not look correct for a 340, I used a 73 340 choke on my Duster with a TQ and the rod was straight. I got mine from Rock Auto. LINK I would also like to find out if the resister is available new, I need one for my Charger, and have had no luck finding one.

Re: 1973 340 Choke Thermostat [Re: T2R9] #966087
04/05/11 05:21 PM
04/05/11 05:21 PM
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Iowa
burdar Offline
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I found a resistor on E-bay but it was NOS and I didn't really want to spend that much.

I'm almost possitive the 4-barrel cars had an angled rod. The carbs are a lot wider so a straight rod wouldn't work.

Last edited by burdar; 04/05/11 05:27 PM.
Re: 1973 340 Choke Thermostat [Re: burdar] #966088
04/05/11 06:19 PM
04/05/11 06:19 PM
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Lets say the crossover is blocked off such as with the Edelbrock heads. After the car warms up, do you constantly power the choke thermostat to keep it open? Or will the thermostat burn up?

Re: 1973 340 Choke Thermostat [Re: 72roadrunnergtx] #966089
04/05/11 08:59 PM
04/05/11 08:59 PM
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Quote:


I believe Nacho’s point was if you go without the controller (don’t power up the heating element and crossover is open) there will be sufficient heat to open the choke, just later than originally designed.





yes, exactly that..

BTW I have a NOS CORRECT choke assistan that could sell BUT dunno about the shipping cost being overseas... killer by fedex/ups/dhl due the cost, but regular postal service maybe is affordable just that will take around a month to get it delivered

with the crossover blocked I would consider the electrical assistant control MANDATORY


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966090
04/06/11 01:40 AM
04/06/11 01:40 AM
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Quote:

Lets say the crossover is blocked off such as with the Edelbrock heads. After the car warms up, do you constantly power the choke thermostat to keep it open? Or will the thermostat burn up?




the power is an automatic feed from control unit as soon you start your engine ( key in run ). If wired like factory did, you don't control that, just ign switch and it decreases the power when engine temp is reached, thats the deal for the control unit. If wasn't in that way wouldn't make sense hook a control unit, instead wire the choke directly from ign switch

Hard to damage the choke really

LATER models ( the round ones ) were also used along with a three prongs oil sender switch, where the power to controil is turned on just when oil sender sense the oil, meaning engine is running. In that way you won't heat the choke just switching on the ign swithc at RUN without start the engine


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: 1973 340 Choke Thermostat [Re: 440newport] #966091
04/06/11 03:50 PM
04/06/11 03:50 PM
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Atlanta Indiana
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Quote:

You can get a modern equivalent that works the same, but they don't look like originals.



Can you tell us what make and model of car uses this style?

Re: 1973 340 Choke Thermostat [Re: Dave Watt] #966092
04/06/11 03:54 PM
04/06/11 03:54 PM
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Valencia, España
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here is the one I'm talking about without the ballast attached and the right one for 73/74


http://cgi.ebay.com/ebaymotors/NOS-1973-...=item53e3e39a7b

not cheap, but mostly sure somewhere somebody will float on another one

or simply get the double stage one and done! will work the same

http://cgi.ebay.com/ebaymotors/NOS-37557...=item35b101fb06

I think in fact you can cut the ballast anyway and will work like a single stage, need to be sure though.

I have both kind NOS, will check casted number on white plastic to check if PN matches, and just service PN is diff due teh ballast


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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