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Thread: 4160 870 cfm unpredictable flooding & stalling.

  1. #1

    Default 4160 870 cfm unpredictable flooding & stalling.

    Hello everyone. I have a hunch this issue has been discussed several ways and I have read several threads, tried just about everything and still can't solve it. I have a Backdraft Cobra, 1500 miles, with a Roush 427R 550 hp engine. Carb is a 4160/80870 dual feed single pumper 870 cfm, electric choke, MSD ignition. Car ran fine until a month ago then every now and then the car floods out and stalls while cruising. There is no warning. I know it's flooding because I can smell the gas and it will start if I crank it over with the throttle wide open. Usually takes a couple tries and then it runs fine till the next event which could be immediately or an hour down the road. It happens often, almost every time I drive the car. Car has also developed an occasional flat spot when slowly accelerating. I'm no rookie when it comes to working on carbs. Here is what I have tried to no avail. Maybe some of you can spot something I missed. I replaced the needle and seat in both bowls with Holley replacements. Took both bowls off and cleaned inside of them. Took out the jets and cleaned them. Took out the floats and inspected them. Funny thing is that the car has a metal primary float and a plastic secondary. Don't know if this is normal? Readjusted the float levels with the vehicle running as per Holley specs and set the idle mixture with a vacuum gauge. I even put a fuel regulator and gauge on the fuel line to make sure the fuel pump isn't pushing too much gasoline. New fuel filters. There isn't much left to look at other than removing and completely disassembling the carb. Maybe the power valve. I'm thinking about maybe pulling the tank and checking it for water or other crap but I found nothing when I replaced the filters. Thanks in advance for any help. Love the discussions. Fred

  2. #2
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    Fred, please elaborate on your MSD ignition, what parts are in the system?
    Doesn't sound like a carburetor issue, I've had many Holleys, of all models & years.
    If they're set correctly, they work as designed. Gary
    Regards, Gary

  3. #3

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    Thanks Gary. I'll look at the components tomorrow. What specific info are you looking for? I received another suggestion to check the air bleeds for clogging. Thanks again, Fred
    Last edited by Fred G; 04-07-2019 at 09:09 PM.

  4. #4
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    Hi Fred. Example would be MSD magnetic pickup distributor, 6AL amplifier, Blaster coil, tach adapter, etc. Any one of these, or a intermittent electrical issue could cause your shutdown. I had a glass fuse that was the cause of many shutdowns for me a few years back. That fuse cost me over $200. Gary
    Regards, Gary

  5. #5

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    Gary. Paperwork that came with car shows a MSD 6AL mounted under dash. Blaster SS coil in engine compartment. I can't find the 6AL anywhere. Is it possible the car just has the Blaster SS coil without the other unit. Like I said, I'm not up to par on the MSD systems. MSD Ford magnetic pickup distributor with vacuum advance. New cap & rotor were installed after problem started. Like I stated above, problem is intermittent. I can always get the car to start if I hold the pedal down and crank it for 3 or seconds. I will work the carb end as I'm pretty familiar with the carbs, but I have not dealt with MSD ignitions. Any help/suggestions on that end would be greatly appreciated.

    Got home from work and took both bowls off, cleaned everything, new power valves & gaskets. Result was the same. No big bog down, but definitely not running right so I'm with you on the ignition being the cause. What's next? Fred
    Last edited by Fred G; 04-08-2019 at 06:49 PM.

  6. #6
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    Fred, if you can't find an MSD 6AL fitted, then you need to start at the distributor. If it's a magnetic pickup only, then there is an amp fitted somewhere, or it could all be a self contained RTR, (Ready-To-Run) distributor. Can you check what you have here? Does this "lights out" flood condition only happen under hard braking to a stop, etc.? Gary
    Regards, Gary

  7. #7

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    Gary, I'm definitely putting the cause on the ignition. I cleaned, blew out with air and rebuilt the main parts of the carb and set everything up as per specs. Roush confirmed it is the correct carb. Car runs okay at high RPM under acceleration, but definitely has a stutter and miss at steady low RPM. The bog is still there. Reached out to previous owner and he said the 6AL is hidden behind the glove box, which makes it difficult to get to. Condition happens unpredictably. Have not been able to recreate it. Read a lot of bad things about MSD ignition systems on the Club Cobra forum in the past few days especially the Blaster SS coils. I'm going to try a new coil. It's only 50 bucks. I assume the distributor is a magnetic pickup one. It's an MSD for a Ford that goes with the system. Suggestion? Thanks for all the help. Fred

  8. #8
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    Magnetic pickup failure is common.
    I would clean and retention the magnetic pickup harness connectors, 2-wire purple and green.
    The connector at the distributor end is more common, since exposed to the elements.
    The Blaster SS coil 8207 is a possibility, trouble is the fault disappears.
    The pickup coil should measure at about 700 Ohms, or between 400 to 1300 Ohms. Gary
    Regards, Gary

  9. #9

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    I disconnected & cleaned the connectors a little while back. Getting the coil tomorrow so we will see. Swapping out the pickup will be next. Thanks for the suggestions. Lots of stories about people dumping MSD for Pertronix on the Club Cobra forum. Fred

  10. #10
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    I don't run MSD ignition myself, but I have many friends that do. I have a Pertronix Second Strike on one car. I'm a Club Cobra member as well. Gary
    Regards, Gary

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