Distributor curve help needed

Electrical and Ignition

  1. Ricks70Duster340

    Ricks70Duster340 Child of the King, widower FABO Gold Member

    Messages:
    606
    Likes Received:
    394
    Joined:
    Feb 8, 2021
    Location:
    Sisterdale, TX
    Local Time:
    8:09 AM
    Not sure where to go at this point. The heavy long looped spring obviously did not do what I had expected. There are two springs remaining in the kit (gold and silver) that could replace the heavy long looped one. Neither would bring in timing at lower speeds, I think.
     
  2. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

    Messages:
    12,820
    Likes Received:
    8539
    Joined:
    Feb 7, 2013
    Location:
    Phila. Pa
    Local Time:
    9:09 AM
    Lets see what you got.
    upload_2021-7-16_14-57-45.png

    Still holding the weights back at 1000 rpm.

    Might be better yet if you have a Chrysler light spring in your stash.
    Softer spring rate will have thinner wire and/or more coils.

    With the existing two springs, on the silver spring increase the loop or slightly bend in the sping perch.
    It's the spring tension that is keeping the weight from moving outward with acceleration.
    The tension is a combination of the distance the spring is stretched and the spring rate.

    upload_2021-7-16_15-1-58.png

    Reducing the tension on the primary spring will let the weights move out at lower rpm.
    Advance curve will start earlier
    upload_2021-7-16_15-7-19.png

    Then to delay the heavy spring, bend the long loop perch slightly in.
    upload_2021-7-16_15-12-9.png
     
    • Like Like x 1
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

      Messages:
      12,820
      Likes Received:
      8539
      Joined:
      Feb 7, 2013
      Location:
      Phila. Pa
      Local Time:
      9:09 AM
      Yea. That's why its good to do this stuff step by step.
      Its not as obvious as it first looks.

      Since you changed the gold spring for the silver spring, anything was possible.
      Sometimes the 'soft' spring has more tension so initially applies more force. The books and magazines never mention that.
      Force = spring rate x distance stretched.
       
      Last edited: Jul 16, 2021
    • Ricks70Duster340

      Ricks70Duster340 Child of the King, widower FABO Gold Member

      Messages:
      606
      Likes Received:
      394
      Joined:
      Feb 8, 2021
      Location:
      Sisterdale, TX
      Local Time:
      8:09 AM
      I left those two springs in there and bent the tabs in. I noticed that the two pegs that slide in and out of the crossmember are already 1/2 way in the slot. Strange?

      20210716_142513[1].jpg
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

      Messages:
      12,820
      Likes Received:
      8539
      Joined:
      Feb 7, 2013
      Location:
      Phila. Pa
      Local Time:
      9:09 AM
      Halfway on the long loop would be about half of the advance available. 8.5* crankshaft degrees
      The primary spring should have enough tension to hold the weight at the bottom of the slot.
      Otherwise you will find the timing changing with idle rpm.

      upload_2021-7-16_15-38-38.png

      upload_2021-7-16_15-43-31.png
       
      Last edited: Jul 16, 2021
    • Ricks70Duster340

      Ricks70Duster340 Child of the King, widower FABO Gold Member

      Messages:
      606
      Likes Received:
      394
      Joined:
      Feb 8, 2021
      Location:
      Sisterdale, TX
      Local Time:
      8:09 AM
      The heavy long loop spring was preventing the weight from fully retracting. I removed that spring and put in a silver one with the following results:

      500-18*
      1000-19*
      1500-23*
      2000-29*
      2500-34*
      3000-35*
      3500-37*
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

      Messages:
      12,820
      Likes Received:
      8539
      Joined:
      Feb 7, 2013
      Location:
      Phila. Pa
      Local Time:
      9:09 AM
      Well you got it in the ballpark now.
      Hopefully you see what the different adjustments do now.

      I'd like to see faster rise in the timing from 1200 to 1800 rpm. Especially if you find the engine likes a little less intial (tested in gear) you can set it with less intial and still have the off-idle WOT timing it probably wants. Same if you find the 37 at 3500 is too much at WOT.
      Probably will need something closer to a factory set of springs like used in a 4bbl points car.
      No idea how the long loop spring you have would block the weights but you can take some pics and/or contact halifaxhops.
      Maybe Halifaxhops will have some springs that will work with the points distributor.

      upload_2021-7-16_16-42-51.png

      Next steps are up to you. If you want to continue refining the initial and mechanical, or make a trial with vacuum advance then come back to tuning the initial and mechanical. Depends on your focus and what your plans are. If your taking it to the drag strip or on family cruise thise weekend can shift the test plan big time!

      If you do hook up the vac advance, the timing from 2500 - 3000 may contribute to pinging when cruising. Its borderline right there depending on the vac advance and the engine specifics. Yes the vac advance can be adjusted to some extent but no point in making major mods there if the mechanical advance still needs tweaking.
      A little ping at cruise is tolerable. Any ping under heavy throttle is not.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

      Messages:
      12,820
      Likes Received:
      8539
      Joined:
      Feb 7, 2013
      Location:
      Phila. Pa
      Local Time:
      9:09 AM
      Sure looks like the weight is free to move in this photo. huh-gif.gif
      20210716_142513-1-jpg.jpg
       
    • Ricks70Duster340

      Ricks70Duster340 Child of the King, widower FABO Gold Member

      Messages:
      606
      Likes Received:
      394
      Joined:
      Feb 8, 2021
      Location:
      Sisterdale, TX
      Local Time:
      8:09 AM
      Really appreciate you working with me on this. I'll drive it tomorrow morning and see what we have. That garage was so hot this afternoon that it ran me out and into the shower!

      When I pulled the top off, the weight connected to the heavy spring was not fully retracted. The spring was on the pin but had a lot of slop in it so did not provide any tension. After this change I did see the idle drop from 750 to 650 in gear. Was a bigger drop before making these changes. Tomorrow's test will tell more. Thanks again!
       
      • Like Like x 1
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

        Messages:
        21,459
        Likes Received:
        8688
        Joined:
        Jan 19, 2014
        Location:
        South-Central Manitoba,Canada, 900ftelevation
        Local Time:
        8:09 AM
        Are your Post #1numbers with the V-can defeated?
         
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

        Messages:
        12,820
        Likes Received:
        8539
        Joined:
        Feb 7, 2013
        Location:
        Phila. Pa
        Local Time:
        9:09 AM
        Sounds good. Cool off!
        I've got to get ready for two days playing in the sun and rain. :rolleyes::realcrazy:

        Exactly

        It will retract from the motion of the governor plate.
        The primary spring needs to pull its weight against the inside of its slot.
        The secondary weight will then follow. There may be a little slop between the slot and the second weight's pin. That's OK.

        Here's an ugly example. You can see ther secondary weight has some play but the primary one is tight to the inside.
        upload_2021-7-16_18-54-7.png

        There needs to be enough side play between the slots and the pins so they run free. The machining on most of these are not that precise. It doesn't effect operation and sometimes even helps it.

        A cleaner example (with a heavier primary spring installed).
        upload_2021-7-16_18-51-43.png


        Direct Connection race distributor (no vac advance) initial.
        upload_2021-7-16_18-45-11.png

        When the governor plate has rotated enough degrees, the secondary spring will engage its weight and slow the advance.
        upload_2021-7-16_18-48-24.png
         
      • Ricks70Duster340

        Ricks70Duster340 Child of the King, widower FABO Gold Member

        Messages:
        606
        Likes Received:
        394
        Joined:
        Feb 8, 2021
        Location:
        Sisterdale, TX
        Local Time:
        8:09 AM
        Yes, the can was unplugged.
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

        Messages:
        21,459
        Likes Received:
        8688
        Joined:
        Jan 19, 2014
        Location:
        South-Central Manitoba,Canada, 900ftelevation
        Local Time:
        8:09 AM
        Well then yes, I would limit the cam to 20* and reset the power-timing to in the range of; 34* at 3200 to 36* at 3600, and just drive it. This should make the Idle-timing to be 20 degrees less, which should be lots.
        If you need more power below stall, the right thing to do is increase the cylinder pressure.
        If you need more power at low speed then you need a higher stall.
        If the power sucks all the time in first gear, you need a bigger number rear gear. Or a bigger engine.
        If you just need a lil more power at Part Throttle and low speed, get more timing from the Vcan.
        My stocker made 22*. @TrailBeast got 24* out of his. Just map out at what throttle opening yours starts dropping off, and run in the zone, for max torque. I installed a vacuum gauge on the signal line, to tell me where I was on the throttle. Easy-Peasy.

        BTW
        I run that one-long loop 318 spring and it is what helps my combo run 87E10 at 11/1 Scr; by delaying my "all-in" to ~3400rpm.
        The little one gets me 28*@2800 starting from 14* initial at about 900/1000rpm. Great curve for my combo. Yes it had more torque with more low-rpm timing, but if smokes the tires just the same with less timing,lol.
        My V-can brings 22* to the table any time the throttle is reduced. By 1600 or so, at PT, the timing is getting to be over 40, and by 2000, it could be as high as 44. At 2800 with the Vcan it could be 50* and all-in, with the Vcan, it could be 56*, and to that I can add up to 6 more with the dial-back.
        The dial back is also great for starting because with it, I can take 9* out during cranking so it cranks on 5*. Then as soon as it starts (cold) I can dial all 15 back in for 20* at idle, during the warm up, so no choke is needed. Then, after the warm up, I take the 6 out again, and leave it alone. All from the saddle.
         
        Last edited: Jul 16, 2021
      • Bewy

        Bewy Well-Known Member

        Messages:
        1,076
        Likes Received:
        650
        Joined:
        Jan 1, 2021
        Location:
        Australia
        Local Time:
        12:09 AM
        Post #29. Pic shows 8.5 on the T piece. That is cam degrees, not crank degrees, Correct?
         
        • Agree Agree x 2
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

          Messages:
          21,459
          Likes Received:
          8688
          Joined:
          Jan 19, 2014
          Location:
          South-Central Manitoba,Canada, 900ftelevation
          Local Time:
          8:09 AM
          yes; at the crank that would be 17*
           
        • dartfreak75

          dartfreak75 Restore it, Dont part it! FABO Gold Member

          Messages:
          10,764
          Likes Received:
          8359
          Joined:
          Aug 10, 2011
          Location:
          Virginia
          Local Time:
          9:09 AM
          Multiply that by 2 to get your total mechanical advance.
           
        1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
          By continuing to use this site, you are consenting to our use of cookies.