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BS Tech: Pro Tuning Secrets

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  • BS Tech: Pro Tuning Secrets

    (Words and Photos by Scott Liggett) -#The proof is in the numbers. In our first part to this article we followed Yannick Sire of Sire Custom Performance take an old crusty GM HEI and do a little magic to it to find a few more horsepower. With nothing more than a little time, a bit [...]

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  • #2
    Neat set up and great write up again Scott.

    What I find interesting is the change in HP at peak for the same total timing. Does the engine just have a better acceleration run going when it hit's peak so it increases the peak HP too? Is that what we are seeing?
    Escaped on a technicality.

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    • #3
      We're limiting total mechanical advance to 18* by welding part of the slot. The weight and springs allow that advance at a much faster rate and earlier rpm.
      Also, some stock distributor's mechanical advance allow as much as 27*. If your only works with 36* total timing. That means you can only have 9* initial. On a stock low compression motor with dished pistons wahy below the deck,you can tbrow over 42* advance before they start having problems. With those lousy quench you need a ton of ignition advance so the flame has a chance to travel.
      Last edited by Scott Liggett; March 30, 2012, 01:52 PM.
      BS'er formally known as Rebeldryver

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      • #4
        You're running 20* initial?
        Escaped on a technicality.

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        • #5
          For the test I did. Normally I run 18* initial, 36 total.

          The problem with my engine combo is that my pistons are .024 below deck and dished and the Vic Jr head chambers are designed for domed pistons. I bet I could pick up 50 hp by zero decking tbe block to for 11:1 pistons.
          BS'er formally known as Rebeldryver

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          • #6
            Good work Scott

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            • #7
              i posted the distributor tuning secrets in another forum and this one person is a non believer ....

              Ya know, the more I read the articles the more problems I had with them.

              First off, neither one of those distributors looks right to me. Hate to point it out but both the stock one they used from the junkyard and the "modified" one, the weights aren't retracting fully on either one. One of the advance weights is hanging out a bit on both distributors.

              On stock HEIs the "head" of each weight should rest against the "tail" of the other when fully retracted.

              On the Moroso kit the heads of each weight should rest against the centerplate when fully retracted.

              I'd say both of them have issues- likely the pins the weights rotate around are worn. A very common problem with old HEIs. And no recurve kit is going to fix it.

              Also, they ran both engines at 38* total timing. One makes 20 more HP than the other at that same setting? How does that have anything to do with the timing curve? By 3000 or so the centrifugal advance is done. But the "modified" distributor continues to outperform the stock one all the way up to redline.

              I just question exactly what they are measuring in this test. Whatever it was that made the difference it ain't the timing curve. Only thing centrifugal advance affects is at what RPM it gets there. Above that point 38* is 38*. When you're there, you're there. End of story.
              "if it's too loud you're too old !!! "sigpic

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              • #8
                nice write up.

                the tune is not just a peak to look at, you gained even more way down at 2000 to 2500.
                daily driving is a real notice down low like that.
                nice work.
                Previously boxer3main
                the death rate and fairy tales cannot kill the nature left behind.

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