Distributor advance springs

Electrical & Ignition

  1. VitaminCRR

    VitaminCRR FBBO Gold Member FBBO Gold Member

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    Back when I was a kid and had a 69 383 RR one of the performance "tricks" we did was to remove one of the advance weight springs down inside the distributor. This would let the distributor reach full advance a lot earlier. I don't remember if it was the light spring or the heavy spring that we removed. Anybody heard of this or do this and know which spring to remove?
     
  2. JimCoronette

    JimCoronette Well-Known Member

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    Replace the heavy spring with one from the kit. Brings timing all in by around 2400 rpms
     
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    • AR67GTX

      AR67GTX Well-Known Member

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      The heavy spring usually has some slack in it so that it doesn’t come into play until the centrifugal advance is partly in. Then it slows down the advance curve so that full advance doesn’t arrive until higher rpm. That can sometimes be a benefit in a heavy car that tends to ping when all the advance is suddenly slung in on WOT at lower rpm. Sort of a 2 stage advance curve. Changing out the smaller spring only will bring in the initial centrifugal advance quicker but the it will sort of flatten out until the rpms increase enough to start stretching the heavy spring. Change out the smaller spring and all the advance will come in earlier - more of a uniform single stage curve - which is good if your engine tolerates it OK. I’m no expert but in recent years I’ve modified the curve in my cars to allow 15 - 16 degrees initial advance with 16 - 20 degrees centrifugal (depending on the engine/car) that comes in a little slower overall. Seems to work well for me on the street.
       
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      • Shorthorse

        Shorthorse Well-Known Member

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        • toolmanmike

          toolmanmike Moderator Staff Member FBBO Gold Member

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