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Hot Rods 6x2 sbc carb issues

Discussion in 'The Hokey Ass Message Board' started by Drivinford, Dec 14, 2019.

  1. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 407

    28 Ford PU
    Member
    from Upstate NY

    It was touched on earlier get a AFR gauge on it or you’ll be guessing for the rest of your life. I also agree big time to balance the air flow with a unisync.

    Keep all carbs identical. If your jetting put the some size jet in all of them.

    You need a ton of initial timing. I would shoot for 20 initial 35 total with it all in by 2500.


    Sent from my iPad using The H.A.M.B. mobile app
     
  2. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    When I use that vac port the car runs like crap? If I put the vac where I drilled it will run, once I take it off and put it on the vac port supplied with the carb it runs worse, am I missing something? Thanks!
     
  3. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    What's a afr gauge?
     
  4. Air Fuel Ratio gauge.
     
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  5. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    When u say a initial timing at 20, and 35 all in by 2500, how do I go about setting that? Thanks alot
     
  6. Pat
    Joined: Jan 6, 2002
    Posts: 122

    Pat
    Member

    I ran a sbc X-1 with 6x2’s straight linkage, fairly healthy 240@ .050 cam. The key for me was getting all the throttle blades even before installing the linkage. Dialing it in at idle with a uni-sync was the next step. Mech advance distributor. Mine wanted about 3.5 psi. 43 jets center 45 jets outer. Used a holley low pressure reg with a stock carter mech pump. This was before I owned a wideband o2 sensor. So it took several full throttle passes down the street to read the plugs to get the jetting right.
     
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  7. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 886

    Jmountainjr
    ALLIANCE MEMBER

    I not trying to be critical, but it sounds like you are bouncing around a bit expecting that running a 6x2 straight up is as easy as a single four barrel. It's not, and as I said in an earlier post, it's a process. Establish a base line and then change one thing at a time. So in no particular order, here are some of my observations:
    1. If you have not taken the linkage off to set each carb initial throttle plate setting you need to do that. Spend $25 - $30 on a Uni-Sync and it will save you more than enough time and grief to pay for itself.
    2. If you are good at reading plugs and general tuning, you can get by without an AFR gauge. If you are new to this, weld in a couple bungs and be able to get an O2 sensor on each bank and be able to see what's really going on with your AFR under each driving condition.
    3. As to vac advance, or not, I think at least initially take it out of the equation. You can play with it later if you want. If you do go back to it, measure the vac in the intake manifold and at the carb vac port and see which value works best with the vac can that you have on the distributor. If you try just mechanical advance, the springs and weights in the distributor is where you tune the timing and amount of advance. To check how it's behaving now you will need to put a timing tape on your dampener and watch with your timing light. Then you can work from there, or send the distributor guy to get it set up on a machine.
    4. You are changing a bunch of main jets, but at the moment it sounds like your issue happens when you are trying to accelerate. That's not main jets. First I will say until it's fully sorted out, ease down on the pedal and don't smash it on like a light switch. It sounds like you are getting a backfire under initial acceleration which could be a lean fuel condition or an ignition issue. Lacking an AFR gauge, have you tried moving the accelerator pump arm settings to adjust the pump shot to see how it helps / hurts? I would start with them all at the low setting and then go richer from there.
     
  8. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,455

    sunbeam
    Member

    Sounds like to much carb to quick. Not to many engines tolerate 900 CFM off idle. It takes air flow to pull fuel into a carb low air = low fuel
     
    Last edited: Dec 27, 2019
  9. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    I appreciate it man, getting info like this helps out so much, I'm honestly just trying to learn this stuff, dont really know much about carbs!
     
  10. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 886

    Jmountainjr
    ALLIANCE MEMBER

    If it was easy everyone would be running them. And you are starting to learn about carbs on one of the most complicated setups around. I admire you for running all 6 and not dummy up 4 of them like on 98% of the 6x2s that you see out there. Read a lot. You Tube can be OK, just know that it's not all good information. If you can, find some local that might have some experience with such things. And don't back away if he is old and gray!
     
  11. DERPR30
    Joined: Jun 3, 2010
    Posts: 782

    DERPR30
    Member
    from HARVEY LA

    I agree with WICARNUT just block off the end carbs it will still run good
     
  12. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 407

    28 Ford PU
    Member
    from Upstate NY

    Search “total timing “ on u-tube.


    Sent from my iPad using The H.A.M.B. mobile app
     
  13. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    If I ease into the gas it seems like it loads up and wants to fall on its face
     
  14. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 886

    Jmountainjr
    ALLIANCE MEMBER

    What indicators make you say it seems to load up? And does it actually bog, or fall on its face? And if it does, does it recover?
     
  15. Joe H
    Joined: Feb 10, 2008
    Posts: 794

    Joe H
    Member

    Close off the outer four, then run off the two center, you are having air velocity problems. To many open throttle blades, means each carb has way less air flow then it needs. When moving off idle, the transition ports do not have required air velocity to pull enough fuel, thus the lean bog or stumble.

    Its easy enough to check with four cardboard block off gaskets. Get the two centers to run correctly, then add the outers with progressive linkage. All the other modifications are just covering up the real problem, air velocity!
     
  16. Drivinford
    Joined: Aug 24, 2012
    Posts: 658

    Drivinford
    Member

    Thank you for your advice!!
     

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