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Manual Choke conversion - help please

Discussion in 'A Body: Duster, Valiant, Dart, etc' started by Graham, Aug 12, 2016.

  1. Graham

    Graham New Member

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    I have a 1966 VC valiant with the standard single barrel carburetor. After many dramas with the original exhaust manifold I have succumbed to fitting extractors. It's a daily drive so at the same time I think it will be best to change to a manual choke. The auto choke never worked great anyway.

    Never done a manual chock conversion before so any advice would be appreciated - type, things to pay particular attention to etc. All advice welcomed and appreciated.

    Thanks
     
  2. ImperialCrown

    ImperialCrown Moderator
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    Is this a Carter YF or Holley 1920 1-bbl carburetor like we have here in the states?
    Is there a tag or model# stamped on the body?
    I have not had good luck with manual chokes on these. Most are homemade/cobbled together and run worse than the automatic chokes.
    If there is any possibility of saving the auto-choke, that would be the preferred method.
    An electric (heated) choke, if one could be fitted to your application would be better.
    Make sure that the vacuum choke pull-off diaphragm isn't leaking and is adjusted correctly.
     
    Bob Lincoln likes this.
  3. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    I would also save the automatic choke, or as IC said, rig up an electrically-heated automatic choke. Too hard to regulate a manual choke properly, too easy to forget to open it.

    My dad once owned a 1955 Chevy Bel Air. It would be worth a fortune today. I asked him what happened to it, and he said the choke was sticking, and a friend rigged up a manual choke.
    "Why did you get rid of it," I asked.
    He said, "I think it started burning oil."
     
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  4. LouJC

    LouJC Well-Known Member

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    I agree with keeping the auto choke. The problem with manual choke conversion kits is that they are cobbled together, low quality parts that bend and flex.
    Years ago (1977/78) we had a 1970 Ford Torino with a 302 V8 and Autolite 2bbl carb. The choke would not open on this vehicle, none of the mechanics we took it to could figure it out. I put in one of those kits and I was the only one in our family of drivers who could start it! And remembered to push it in! So finally I got a Ford shop manual and studied how that choke was supposed to work....
    Hot air choke fed by the pipe that fit into a passage in the pass side exhaust manifold. Hot air supposed to be sucked in by engine vaccum into the choke housing past the thermo spring. Well, here's what the problem was, too much play in the choke linkage shaft that went through the housing, causing a vacuum leak! And not enough hot air. I found the vac leak by spraying a little light oil on the shaft. Got sucked right in. Fix was, to find some fiber washers that would reduce the side to side play in the choke shaft and allow enough hot air to get sucked past that spring.

    As a general guide auto chokes can be kept working well if you:
    Keep the linkage & choke plate clean, a little grit on it or even oil will keep it from moving, those thermo springs do not have much tension even when new.
    Make sure the way that the choke is supposed to get heated, really works (my problem above).

    I also had some issues with the auto choke on my boat's Rochester Quadrajet (divorced choke, spring heated by exhaust gas cross over in the intake manifold). The spring was OK but it was slow to open, I started cleaning the linkage and choke pivots every season and that helped. This problem was also exacerbated by the nature of raw water cooled boat engines, they come with low temp thermostats so they never run as hot as the auto version (160*F, normal temps are 160-175). I wound up setting this one so it just closed on a cold engine, this one did not need as much choke as some because you could set the idle mixture fairly rich to keep it from stalling when cold.
     
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  5. pt006

    pt006 Active Member

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    Graham; I agree with the others. I'd keep the auto choke. They work quite well with a little maintenance. Most problems are due to a sticky or stuck heat control valve. It is the flap valve located on the lower part of the exhaust manifold. It should rotate easily. It is spring loaded in one direction when the engine is cold. This allows the hot exhaust gasses to heat up the base of the intake manifold and the choke spring area, which opens the choke faster. Another common problem is the choke pull-off. It is a vacuum 'piston' made of rubber which opens a closed choke. To a point where an engine runs well when it is cold. It is adjustable by bending a rod to a set length. I think the choke plate to carb housing dimension is ~ 1/4".

    Some of the later [1970's] cars had a choke spring heater. This must be used with a 'choke controller'. It is a little rectangular box which also shuts off the heater at a certain temperature. Your intake manifold might be different.

    Installing the intake/exhaust manifolds on a slant 6 is almost a science. Special tapered jamming nuts and special tapered washers must be used on the ends. And torqued properly!!!! Note that the outer exhaust port flanges are designed to slide on the head surface with temp. changes. If they do not slide, it is possible that the exhaust manifold will crack.

    Good luck.
     
  6. Graham

    Graham New Member

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    Thanks for all the feedback - really appreciate it. Being an aussie hemi it has the Carter 1bbl carby. It is only now, through experience, that I have come to appreciate the science that goes along with fitting the exhaust manifold. It's hard to find someone with the knowledge and experience to do it properly. That is why after the exhaust manifold was cracked due the the mechanic over tightening the nuts on a fat gasket (and not using an original steel gasket) that I succumbed and decided to go to extractors. Fortunately, they don't sound as loud as I thought they would and it certainly allows the slant to run more freely. The challenge now is to rig up an auto choke using the extractor pipes as the heat source. Has anyone had experience doing this?

    Thanks for the advice on the vacuum system. - another good reason to try to keep some sort of auto choke system in play.
     
  7. ImperialCrown

    ImperialCrown Moderator
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    This is an article on the Aussie Hemi 6 that we didn't see here in the U.S.:
    Australian Hemi Six Engines: 215, 245, 265
    You might want to look for a choke assembly that fastens to the side of the Carter carb body. Ford used this set-up almost exclusively on their 6 cylinders.
    Electrically heated kits were available to convert them from exhaust heat to electric heat. It was just more reliable.
    Dorman made an electric thermostatic choke conversion kit. This following discussion isn't about a Mopar, but a Ford with the same issue:
    Carter YF electric choke conversion? | Maverick/Comet Forums
    I also remember the rubber heater hose fastened up against the side of the choke body for faster choke warm-up on the Fords.
    Some auto-choke history and methods:
    THE CARBURETOR SHOP / Automatic chokes
     
  8. CudaPete

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    Back in the day, I installed manual choke conversions on a few applications, /6, Chevrolet, AMC, etc. All have been relatively easy and reliable. Drill a hole in the firewall, install a grommet, and the cable. Disconnect auto choke linkage and connect cable. Sometimes it takes a little imagination but certainly doable. Last one I did was back in 89 on a Matador, 232 I6, with the Carter BBS. Very simple since the BBS may have been designed with a manual choke to begin with.
     
  9. Graham

    Graham New Member

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    Thanks again for the advice. I will ask around about the availability of an electric choke that would be easy to fit (unlikely I suspect). I think I may try a manual choke in the first instance. It will be a lot less mucking around than trying to adapt extractors to accommodate an auto choke I think. If I had replaced the original manifold with a new one I wouldn't change the choke configuration.

    Given I'm the only one who drives the car I will be the only one to blame if I leave the choke on!
     

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