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  1. #1
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    Default How far open should carb choke flap be when hot?

    Is this far enough?
    '72 350 Qjet



    Also when closed and cold engine should it be "completely" closed?

    ...and finally, can I use aluminum tape to cover those holes someone drilled in the back flaps?
    -Jason
    __________________________
    She ain't heavy, she's my Buick.

  2. #2
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    Default Re: How far open should carb choke flap be when hot?

    Primary air blades are correctly open when hot.

    As for the secondary air blades, just replace them....if you don't have any, I do. DO NOT use tape....that can come off and end up going into the engine.
    George Nenadovich
    Buick Performance Club Founder
    www.BuickPerformanceClub.com

  3. #3
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    3,678

    Default Re: How far open should carb choke flap be when hot?

    Hot engine choke plate should be vertical. Cold, engine off, it should be closed completely and open slightly when engine is started.
    No, its not a chevy motor

    Steve Mario

    '71 Skylark, street/strip beater w/JW and T/A goodies!

    (JW prepped 462 short block, ported T/A Stage 1 TE heads w/stage 3 valves, 1050 Dominator, Super Scavenger headers, 3400 stall TH400, runs on pump gas, and leaves brown skid marks on the passenger seat.)

  4. #4
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    Lawrenceburg, Tn.
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    Default Re: How far open should carb choke flap be when hot?

    The old school method was to take a 1/8'' drill and set the choke to where it just touched the drill when completely cold,,,, that allowed for the engine to get its breath and still richen the mixture enough to run cold.....
    Doc "Widely unknown"

  5. #5
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    Default Re: How far open should carb choke flap be when hot?

    Mine is about completely closed when cold, but the car won't just pop off and idle, its still cold blooded. My mixture screws are at 2 3/4 turns out. Maybe I just need to turn up the idle screw? When it is warm it has a nice low idle where it currently is.
    -Jason
    __________________________
    She ain't heavy, she's my Buick.

  6. #6
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    Default Re: How far open should carb choke flap be when hot?

    It is not your idle screw....you need to adjust your fast idle screw on the pass side.
    George Nenadovich
    Buick Performance Club Founder
    www.BuickPerformanceClub.com

  7. #7
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    Default Re: How far open should carb choke flap be when hot?

    Quote Originally Posted by GStage1 View Post
    It is not your idle screw....you need to adjust your fast idle screw on the pass side.
    Just turn 'er clockwise a bit? If you could help me out, what does that "fast idle" do, is that basically the (startup/cold idle)?
    -Jason
    __________________________
    She ain't heavy, she's my Buick.

  8. #8
    Join Date
    Feb 2008
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    Lake Forest Park, Washington
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    Default Re: How far open should carb choke flap be when hot?

    Quote Originally Posted by buicks View Post
    Just turn 'er clockwise a bit? If you could help me out, what does that "fast idle" do, is that basically the (startup/cold idle)?
    Pretty much, as far as I'm aware it just boosts idle while car is warming up and then gets ignored as soon as you put it into gear.
    Chris

    1973 Electra 225 Limited. (Glossy black with white road paint flakes) 455/ TCI turbo 400.
    1972 Skylark Custom.( Pumpkin Orange) 350/350
    1972 Skylark (Death-mobile Black) 350/350
    1999 Izuzu Hombre (S-10)

    Only 21 and I've already owned 8 cars! I'm on a roll.

  9. #9
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    Oakland Gardens, N.Y.
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    Default Re: How far open should carb choke flap be when hot?

    Quote Originally Posted by buicks View Post
    Mine is about completely closed when cold, but the car won't just pop off and idle, its still cold blooded. My mixture screws are at 2 3/4 turns out. Maybe I just need to turn up the idle screw? When it is warm it has a nice low idle where it currently is.
    It looks to me like you have an aluminum intake manifold so you couldn't be using the stock choke coil.

    This is how things work. In a stock setup(cast iron intake), there is a bi metallic coil(choke coil) that sits in a recess in the intake manifold. It has a link to the choke blade in the carburetor. The choke blade rotates from full closed to full open. As it does, it moves a fast idle cam which controls fast idle speed. The fast idle screw (passenger side) sits on the cam and boosts the idle speed. The cam has various steps so that as the choke blade opens, the idle speed drops until the cam rotates enough so that the screw falls off the cam and idle speed is controlled by the curb idle speed screw(drivers side) The choke coil responds to heat in the intake by relaxing and opening the choke, and rotating the fast idle cam. When the engine is cold, the choke coil should close the choke blade completely, and if you open the blade with your finger, it should snap (spring back to closed) much like the secondary air valves do when opened. When the engine starts cold, there is a vacuum operated(primary) choke break that will open the choke a preset amount so that the engine will run without loading up. Some carburetors have a secondary choke break that opens the choke a bit more. These breaks operate so that the engine runs smoothly as it warms up and in the interest of emissions. The rest of the choke opening is controlled by the coil. It responds to heat and relaxes opening the choke the rest of the way. All of this is adjustable by bending the links and adjusting the fast idle screw. A popular performance mod for stock iron intakes is to block the exhaust heat cross over. This blocks heat to the choke coil. The intake runs cooler for more power, but the choke will not open because the coil doesn't get hot quick enough.

    Being that you have an aluminum intake, you are using an aftermarket choke coil. It may be the wrong one, or it may need to be adjusted. George has an article on choke mods for aluminum intakes here: http://www.buickperformance.com/Edelbrockmods.htm
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    Best E.T. 11.54@ 115.00. Best MPH, 11.58@ 115.89
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  10. #10
    Join Date
    Apr 2009
    Location
    Georgia
    Posts
    25

    Default Re: How far open should carb choke flap be when hot?

    I agree with him ^_^
    Curris hinc. Hic detestatus est.

  11. #11
    Join Date
    Mar 2004
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    Minnesota
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    Cool Re: How far open should carb choke flap be when hot?

    Thanks. Yep I have a TA stage 1 aluminum intake, I also have headers and 2.5 inch exhaust with unrestrictive mufflers and an x pipe. I didn't block anything off when installing the intake. The choke coil I have was the recommended one by TA preformance for the intake and is installed on top if the intake. However I had to remove the "cover" that came with it in order to get a bent wire to work from the coil to the linkage(since it didn't come from TA with a wire of any kind to connect the two. The choke is closed all the way when cold but not quite vertical when hot, it does come back closed when I push it open by finger but not "stiffly". I am sure the "fast idle" screw is set wrong becuase I havent touched it, but the mixture and idle screws are set for good running when hot. It may be a tad rich but I do not know how to tell (other than no black in exhaust).
    p.s. I did notice in that link you supplied, that the coil in his pics is more tightly wound than mine, the end of mine juts out twards the front of the car even when cold instead of being as tightly wound as the rest, maybe bending the end of mine a little tigher would help.
    -Jason
    __________________________
    She ain't heavy, she's my Buick.

  12. #12
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    Default Re: How far open should carb choke flap be when hot?

    To set the idle mixture screws......start 1 turn out and adjust them out while you have a vacuum gage connected to an intake port....you want max vacuum when adjusting the idle screws...typically 1.5 to 3 turns out.
    George Nenadovich
    Buick Performance Club Founder
    www.BuickPerformanceClub.com

  13. #13
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    Default Re: How far open should carb choke flap be when hot?

    Yep my mixture screws are both 2.5 turns out.
    -Jason
    __________________________
    She ain't heavy, she's my Buick.

 

 

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