Distributor starting point for a curve

Great distributor mechanical curve sheet. All makes
  1. halifaxhops

    halifaxhops It's going to get stupid around here! FABO Gold Member

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  2. 67Dart273

    67Dart273 Well-Known Member

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    Link does not work. AbodyJoe pasted up a magazine article some time ago that covers this.......Post 28

    how much initial timing mild 360 magnum

    Crackedback came up with a chart that shows some idea of stock distributor slots to degrees advance.......

    Dimensions for Mopar distributor slots, in DISTRIBUTOR degrees

    Modifying advance slots
    degrees / slot size
    6.............. .340
    7................355
    8................375
    9................390
    10...............405
    11.5 ...........420
    12...............435
    13...............445
    14...............460
    15...............475
    16...............490
    17...............505
    18...............520
     
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    • jas0162

      jas0162 Well-Known Member

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      Sweet. I always guess then have to take it back apart again. Thank you much
       
    • 67Dart273

      67Dart273 Well-Known Member

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      Were you able to open the links? I got an error
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      See if this works.
      Initial Timing - Carb Chart (at Archive.org)
      Originally was on the now defunct Barry Grant - Demon website.

      This is for ball park setting of the initial timing based on engine displacement and cam duration.
       
    • halifaxhops

      halifaxhops It's going to get stupid around here! FABO Gold Member

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      That is great to have the only issue is you need to know the location to put it you just cant open them up and have it work to far in it restricts the advance. FBO plates are great way to limit advance, just have to be carefull to make them go further advanced
       
      Last edited: Apr 30, 2018
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        The FBO plates require a lot of fiddling or the curve is too much at low rpm and then gets cut off too early. With a distributor machine and knowledge its easier to do that (use the plates and then change or adjust springs to get it right ).
        Easier for most people looking for more performance not to fiddle with springs etc. The way to do that is to shorten the inside of the slots. That way the only part of the curve cut off is the beginning. Then set the intial like a non-CAP equivalent, or use that chart linked above for a modified engine.

        The reason for shortening the beginning is many emission era distributors have fast long advances off-idle to make up for reduced initial timing. Initial timing was reduced starting with CAP to reduce emissions at idle speed. (This is OK when everything is setup 100% stock but not when things get modified.)

        Racers used to set timing at mid or high rpm and not worry so much about initial. OK with some distributors but less than ideal; especially with street driven automatic transmission cars.
         
        Last edited: Apr 30, 2018
      • 67Dart273

        67Dart273 Well-Known Member

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        It was discussed here once. "Back in the days" some of us used to just yank the springs off and time it "total." These were dual point dist, and the points cause enough "drag" to retard the thing for startup. I variously ran (in a 426W, 440, 340) the stock Prestolite dual point, Accel which used GM points, a "hemi" tach drive, and 340 Prestolite stocker. I variously used the big rectangular Mallory coil, a couple of different (Delta, whatever) CDI, and some other "experiments." "Back then" you could get HEAVY duty Echlin "gold", Standard "Blue Streak" and Accel points. Wish I'd bought a BIG truckload!!!

        This was in the '70s when I was stationed at NAS Miramar, San Diego.
         
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