1973 340 Choke Thermostat
#966073
04/04/11 08:24 PM
04/04/11 08:24 PM
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Dave Watt
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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 page http://www.autozone.com/autozone/parts/D...56_207659_8298_
Last edited by Dave Watt; 04/04/11 08:30 PM.
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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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Joined: Aug 2007
Posts: 6,095 Valencia, España
NachoRT74
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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
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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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Posts: 6,095 Valencia, España
NachoRT74
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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
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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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Joined: Oct 2008
Posts: 765 Shoreline, Washington
72roadrunnergtx
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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.
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Re: 1973 340 Choke Thermostat
[Re: NachoRT74]
#966084
04/05/11 05:07 PM
04/05/11 05:07 PM
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Joined: Feb 2005
Posts: 28,312 Cincinnati, Ohio
Challenger 1
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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.
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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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440newport
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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.
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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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Joined: Aug 2007
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T2R9
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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.
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Re: 1973 340 Choke Thermostat
[Re: T2R9]
#966087
04/05/11 05:21 PM
04/05/11 05:21 PM
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burdar
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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.
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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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Joined: Aug 2007
Posts: 6,095 Valencia, España
NachoRT74
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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
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Re: 1973 340 Choke Thermostat
[Re: 440newport]
#966091
04/06/11 03:50 PM
04/06/11 03:50 PM
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Joined: Nov 2003
Posts: 5,048 Atlanta Indiana
Dave Watt
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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?
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