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How to make a Single Point Setup?

Discussion in 'Technical Q&A' started by 308GTS, Nov 14, 2003.

  1. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    I am curious on how to run a single point setup. I have replaced my points before when I first got my car and then went to the Crane XR700s but I would like to know the procedure for a single point setup. Which point do you keep? I assume the timing has to be bumped up to at least 7 deg. advance. Anyway I would appreciate some info. Thanks.
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,324
    Texas
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    Steve Magnusson
    R1 is the point set you keep (IIIC R2 is not hooked up in a way that would work without a wiring modification if R1 is not present), but if you only had/have 1 Crane XR700 box per distributor then you were/are running in a "single point set-up" (unless I'm misunderstand the term). You've got it right that with a single trigger device in the distributor that lacks some sort of "sharp step" in the low-RPM advance behavoir, you would set the 1000 RPM idle timing to ~7 deg BTDC to match the stock single-point recommendation.
    Personally, I'd put a little $ premium on a healthy R1+R2+microswitch system in a US version (or at least having the hardware in a box) since it makes the carb idle airflow set-up less tweaky (and I guess I'm becoming a stock freak ;)), but understand that the complexity is a downside so most are eventually removed.
     
  3. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Yes, I do have an XR700 per dist. as it is a US spec car and I did keep my points. Personally I don't see the plus side of keeping the R1 and R2 points in the car especially at the price they charge for one point set.
    Anyway, back to the question. You would remove R2 and just keep R1 point sets in each distributor and the wiring wouldn't need to be altered?
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
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    Steve Magnusson
    Yes (but wouldn't it be better to use the optical triggers that came with the XR700s if you're going to a single point architecture? I'd even do the Pertronix trick and put both optical triggers in one distributor at 135 deg mechanical/45 deg electrical).
     
  5. Dave

    Dave F1 Rookie

    Apr 15, 2001
    2,722
    Little Rock
    Full Name:
    David Jones
    I agree with Steve,
    Why not use the optical triggers instead of dick'n around with the points.
     
  6. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Guys I am not going back to single points. I am keeping the XR700s with their optical triggers and using no points at all.
    My question is having no XR700s at all how would you make a single point setup. I have heard about them and a few users used them in the past but I am wondering how you would do it with just the stock setup. Sorry if my question came accross that I was planning to use it. I just wanted to know how to do it. Thanks.
     
  7. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,324
    Texas
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    Steve Magnusson
    Got the picture -- and, just to be complete, you would also remove the 2-wire condensor when you remove the R2 point set (doesn't matter if you leave the wiring harness going to the microswitch or not with the R2 points and the 2-wire condensor removed).
     
  8. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Great so basically you just remove the R2 points and their condensers and that is it, besides adjusting the timing accordingly? Will the car repsond approx. the same way it does with the XR700s or ? since I have never tried the single point setup.
     
  9. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,683
    North shore, MA
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    THE Birdman
    There is a simplifed schematic of the ignition circuit in the owners manual. You can pretty easily see there how the whole thing is wired. Basically, remove (or just unwire) the switch on the throttle cable (near carbs) that switches between the 2 sets of points, then remove (or unwire) the second pair of points and that's about it I think. My car came with the second set already removed, so I never did the mod, but I rewired some flaky ignition wiring when I got the car , so I went through to see what they did. Pretty simple actually.

    My understanding is that the second set of points, along with the high idle mechanism, were purely emissions-related items and removing them doesn't harm the performance of the car, but reduces the number of things that can go wrong.

    Jonathan
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,324
    Texas
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    Steve Magnusson
    IMO yes (assuming both systems are working well)
     

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