Carter AFB Electric Choke Conversion

Discussion in ''Da Nailhead' started by CTX-SLPR, Nov 6, 2006.


    CTX-SLPR Modern Technology User


    Is doing this worth it? Amazingly the stock hotair choke is still working and in decent shape but I'm digging into the exhauste for a TA pipe kit and it wouldn't be a bad time to eliminate the heat choke and go for an electric. I plan on keeping atleast a modified version of the heat crossover though since it is a stock motor and I do drive it in the cold.

  2. nailheadina67

    nailheadina67 Official Nailheader

    I did that on mine and it works great! For the price it's a modification that's well worth the $$. :beer

    What's best about it is that the one I got from napa has a heat sensor that bolts to the engine block. It lets the choke open quicker when the block is warm but the outside air is cold, such as if you parked the car for an hour or so in the cold weather. The choke opens quickly and won't stay closed and idle too fast for a few minutes like the original design does under those conditions. Be careful, some kits don't have this sensor.

    Also, I removed the stainless heat tube from the exhaust manifold (it was cracked anyway) and plugged the holes, that makes for a cleaner look and has less restriction to the flow of exhaust. :TU:
  3. carbking

    carbking carburetion specialist

    It depends on where you live, what type of transmission, and how you drive the car.

    If you have a standard transmission, and don't mind slipping the clutch for a few minutes after starting you can make it work.

    If you live in some area such as Miami, San Diego, or Honolulu, you can make it work.

    If you have an automatic tranny and live in a colder climate; and don't mind going back into the house for a couple of extra cups of coffee after starting the vehicle BEFORE you attempt to put it in gear, you can make it work.

    Otherwise, consider a membership in AAA (for towing insurance) as part of the price of the conversion.

    If you wish to eliminate the hot air choke, then MUCH better to go with a manual choke than with the electric for an older automatic transmission.

  4. doc

    doc Well-Known Member


    Jon is pretty well right on.
    There is one other option, in the 60s Buick used a choke that warmed up from a heater hose going up to it. If you can find the parts to make it work.
    Most chokes are set too tight and take too long to pull off. I set mine to where a 1/8 drill will fit between the lower edge of the choke plate and the body of the carb.with the engine stone cold, preferably on the coldest day of winter. :grin: :grin:
  5. I did the electric choke conversion and it has run great. I don't have a remote sensor so I run into the problem of a cold choke on a warm engine, but it was better than the alternative, a choke not hooked to anything. :grin:
  6. nailheadina67

    nailheadina67 Official Nailheader

    Why would he need towing insurance? If the conversion is done right the car should run great. :error:
  7. carbking

    carbking carburetion specialist

    OK - several assumptions here:

    (1) original automatic transmission
    (2) typical electric choke conversion without rheostat
    (3) must stop at a stopsign (stoplight) or two before hitting the interstate

    The typical electric choke is a timed choke; having NOTHING to do with the warmth of the engine. Most release FULLY in about 45 seconds! The hot air choke was keyed to the actual warmth of the engine, and would not fully release for 5 to 8 minutes, depending on driving speed.

    The engine REQUIRES extra fuel for low speed operation until it warms to operating temperature. The amount is a declining curve based on temperature.

    Typically, with the electric choke. One starts the car with no problems. Starts to drive off, and stops at a stop sign about 3 blocks from the driveway. The choke has fully released, the engine stalls AND WILL NOT RESTART! The operator now calls the AAA towtruck!

    Alternately, one MAY readjust the idle circuit to be exceedingly rich, thus wasting fuel except for the first 10 minutes, to duplicate what the original choke would have done; and the system will work, somewhat.

    While some individuals may be happy with this arrangement; if I had a nickel for every customer who called our shop AFTER installing the electric choke and having these stalling problems, I could purchase the entire state of Florida and retire!!! Well, almost.

    And regardless of the type choke (assuming the choke fully opens), the choke will not effect the fuel curve after the engine is fully warmed. It is just the first 10 minutes that matter to the choke.

    Maybe someday one of the young computer whizzes will develop an electric choke with a built-in computer chip that connects to a sensor in the cooling system and allows the choke to function like the original did; but this would be no improvement over the original. The ONLY improvement (opinion) over the original hot air choke is a manual choke. Others opinions may differ.


    CTX-SLPR Modern Technology User

    1) Stock 425 Nailhead, single stock AFB, ST400 stock transmission
    2) I'd like an effective choke, Right now the hot air works pretty good but not perfectly
    3) Lots of stop signs before the free way and and I drive it in cold weather on occasion

    A coolant sensor is a voltage based sensor, it should be very easy to affect the currect going to the heating coil element based upon the coolant temperature sensor voltage. I believe that is what Joe is reffering to. Ohm's Law is V=I*R so I=V/R, depending on if the sensor is increasing or decreasing resistance in responce to temperature you might be able to run the power for the choke through the sensor and have your current ramp with the coolant temperature. Unfortunately my experience is that things get more resistive as temperature climbs so you'd get max current at cold and it would fall as things warmed up.
    I agree that the standard electric choke pulls off way too fast for most classic engines, my Holley Street Avenger had this problem when I lived in Colorado, it took 5-10 min before I could put it in gear and get out of the parking lot without risking hitting someone and it still ran pig rich at idle in the winter.
  9. carbking

    carbking carburetion specialist

    Since you have the original? AFB with the hot air choke, my suggestion would be to get this choke working as designed. :)

    The most common cause of problems with a hot air choke is a partially clogged vacuum supply line, or one with a defective gasket. :error:

    If one has the carburetor off the engine, and removes the metal choke housing, one can see the vacuum supply line. It begins in the primary throttle area on the passenger side, and runs horizontally toward the passenger side of the carburetor, coming out behind the metal choke housing, where it is sealed to the choke housing with a neopreme gasket. Now inside the choke housing, the passage makes a couple of 90 degree bends and exits beneath the piston assembly located in the choke housing.

    The piston assembly was an integral form of a choke-pull-off. The vacuum pulls the piston against the choke spring, allowing the choke butterfly to open AS THE SPRING RELEASES.

    The vacuum escapes from around the piston, thus creating a vacuum on the inside of the entire choke housing. This is sealed by the gasket under the plastic choke cover. Since the hot air tube is connected to this vacuum, hot air from the crossover, is pulled into the choke housing, allowing the spring to relax as it is warmed, thus the choke is "in time" with the temperature of the engine.

    A faulty gasket or a partially clogged passage will slow dramatically the amount of hot air pulled into the choke housing, and will thus fowl up the "choke timing". Very seldom does the spring go bad, and many chokestats have been sold when the only problem was a defective gasket.

    Adjustment of the choke is very easy. Forget about the markings. Simply pick a day when the ambient (ourside, or your garage) is between 65 and 70 degrees F (68 degrees is the perfect temperature). Adjust the choke cap should that the butterfly will just TOUCH closed on a cold engine at this temperature, and your choke is adjusted.

    Opinion - this type of choke is the perfect choke, if one wants an automatic choke. The divorced choke is less perfect, as it must also overcome the mass of the operation rod, and requires a divorced choke pull-off (plastic, that fails over time). The water heated chokes fail from corrosion. The electric choke, devised at least as early as the mid 1930's, found no wide-spread use until the late 1970's, when some "wise" individual :spank: at the EPA determined that emissions would be lessened if the choke released earlier. Does anyone remember how well the vehicles in the late 1970's performed in city traffic? :rant: As previously stated, the only choke that will perform better than the hot air choke is a manual choke.

    Oh, and the second most common (maybe 1/100 of 1 percent) choke problem is a burned out heat stove in the manifold. This condition will be readily apparant when one removes the choke cap, as the entire inside will be sooty and corroded.

  10. 12lives

    12lives Engage! - Jean-Luc Picard

    Jon - This has been discussed before, but let me ask again: What if the heat pipe from the exhaust manifold breaks off? 1) can they be replaced (TA???) and 2) is it difficult to do (ie doe it require me to pull the manifold off)? Is there an "easy" fix?

    1967 340 - AFB

    - Bill
  11. carbking

    carbking carburetion specialist

    Bill - this would depend on where it is broken and how.

    If "numbers matching" then the manifold probably needs to be removed and an original repair.

    If not "numbers matching", then depending on the location of the break, a repair is feasible. If the tube is broken from the top of the manifold, the tubing may be "squeezed" so that it may be pressed into the hole in the manifold. If the tubing has rusted or broken such that a piece of it is still present, the next larger size may be used as a "sleeve" to join two sections together. Generally possible to repair.

    Not sure how Buick does the heat tube in the manifold, as I do not have a Buick manifold to inspect. Pontiac, Olds, and Cadillac have a tube pressed into the underside of the manifold through the exhaust crossover. If this tube burns out, then the manifold must be removed, the old tube machined out, and a new tube pressed in.

  12. 12lives

    12lives Engage! - Jean-Luc Picard

    Thanks! If you use the sleeve method, do you apply a sealer or glue (JB Weld??) to the joint?

    - Bill
  13. carbking

    carbking carburetion specialist

    No, crimp it. This can be done by blunting a cutting tool for a tubing cutter.

  14. telriv

    telriv Well-Known Member

    I have been using the NAPA electric choke conversion for years. It is, by far, the best one out there & the only one I sell at my shop. It DOES have a temp. sensing electronic unit that governs how long it will take for the choke to open. Normally, anywhere between 5-8 minutes & it will be fully open. Since it has a temp. sensor the choke won't close because it's not getting any voltage to supply heat to the coil. There is a red wire that's hooked up to an always hot wire that senses the temp. of the engine through the electronic unit. If you ask for one for an AFB they won't have one. You need to ask for one for a Holley or Ford.
  15. CTX-SLPR

    CTX-SLPR Modern Technology User

    Once again Tom coming through in the clutch. Do you have the part number? By the way thanks for the P/N on the KYB shocks for the Riv, ordered them today though the 107 Install kit didn't ring any bells at PST.

  16. nailheadina67

    nailheadina67 Official Nailheader


    Do you even OWN a Buick? Have you ever driven a dual quad Nailhead on a daily basis?

    I have owned mine for my whole life since I was 18........and I'm 47 now. I don't need a carburation professor to tell that something won't work when I know it does. If you prefer to go epoxying things and shoving sleeves down what was a a poorly designed choke system to begin with, then go ahead.

    Carroll asked me as one fellow Buick owner to another comments and suggestions about an electric choke conversion........and I gave my opinion based on what works very well for me.

    No wonder people are reluctant to answer technical questions on this board. :Dou:
  17. CTX-SLPR

    CTX-SLPR Modern Technology User

    I'm not Carroll, I'm Will but I'm just glad that it was an attempt at a personal acknowledgement.
  18. telriv

    telriv Well-Known Member

    Will, I don't know why PST doesn't know what your talking about. It's just like when I tell people to use poly bushings for the top of their shocks. They call & talk to the salesmen & they say "they don't make poly top shock bushings". These bushings are 3/8ths. diameter just like the majority of sway bar link bushings. If you ask for 3/8ths. sway bar link bushings they have them in stock, which I do also. The 107 installation kit is available through Summit or Jegs. You need it to take up the slack at the upper shock bolts. The shocks use a 1/2" bolt & the stock Riv. has 7/16ths. bolts. It's just a sleeve, I get them all the time. You gotta remember about these "salesmen" at these different mail order company's. Probably the majority of them were insurance salesmen last week.
  19. CTX-SLPR

    CTX-SLPR Modern Technology User

    Very true Tom,
    I think I'm going to get the Energy Suspension brand end link bushings from Advance auto for ~$10 for a package of 8 and skip the rear shocks for the time being as they seam to be still doing pretty good, its the front shocks that are blown.
    Any word on the Napa part number or the cost from you on that electric choke kit?

  20. nailheadina67

    nailheadina67 Official Nailheader

    Sorry for that, Will......some of us have our names included in our signatures, I wasn't reading yours as close as I should have. :eek:

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