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B20/B21 distributor questions 120-130

posted by  mario_e on  Tue Aug 2 12:06 CST 2005
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last visit: Wed Sep 17 06:43 CST 2008
[RELATED]

I posted this on another forum and have gotten no responses so I thought Brickboard could help.

The recent chatter about the advantages of vacuum advance has gotten
me thinking.

I have a Volvo electronic ignition from a '75 240 and it works fine
with the vacuum retard blocked off.

I've heard from John Parker that the mid-80's to mid-90's Saab Turbo
has a vacuum pot that will bolt up and can advance instead of retard.
This would be a used option as new they're about $100 for the vac pot.

I've also heard that a '78 B21 has a vacuum pot that may also have
retard/advance but don't know if it will bolt up. Its about $20.

Anyone know B21's?

Lastly, I was digging through my parts boxes and found a points-type
vacuum advance distributor which is my big fallback position. Seems
fine, needs to be cleaned up, new vac pot and I would want to lose the
points.

Bolting a different vacuum pot on the '75 seems easiest.

Thanks for any input.

-Mario E.








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    B20/B21 distributor questions 120-130

    posted by  blackjackmc on  Fri Aug 5 14:40 CST 2005
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    last visit: Mon Jul 27 10:24 CST 2009
    [RELATED]

    Paul. My 74 b20e Grand Lux has vacuum advance standard. My understanding of vac advance is to get additional advance at low load and part throttle over initial timing. Because it matches ignition timing to engine load it must increase fuel economy to some extent by maintaining ideal spark advance at all times. Regards Jack McIntyre.








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      B20/B21 distributor questions 120-130

      posted by  someone claiming to be jparker3 on  Mon Aug 8 03:38 CST 2005 [RELATED]

      Complicated by whether the vacuum source is before or after the throttle butterfly. The source can be changed to modify the advance characteristics and strength. See the article in this month's Classic Motorsports for details.

      John
      V-performance.com








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      B20/B21 distributor questions 120-130

      posted by  CyaLater on  Fri Aug 5 18:59 CST 2005
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      Your's would be a K-Jet car then, yes?
      Does your distributor have an aluminium body & take the mirror image points?

      I got my vacuum advance dizzy & K-Jet system from a '74 wagon. I fitted the K-Jet to my old '70's car & then very much later I put the dizzy in. It made no difference to my car other than give the car a bit of hesitation occasionally on the highway.


      On a different topic. Remember our discussion on Mitsubishi rod strokers à la IADR & Topi style? We can get new H-Beam 4G63 rods in the Eagle brand for $660/set. I also got a quote of just $500 for a set of Scat brand but I'm not sure this is correct as I thought Scat would be dearer than Eagle. Anyhow, do you have any mates in your neck of the woods that can tell us how big the bowl is in 4G54 '94-onwards Magna pistons? ACL 4MKRY2933 is the part number for a set with moly rings.

      PS: please reply directly to this message, so that the board can email me your reply.

      Cheers,
      Paul.







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        B20/B21 distributor questions 120-130

        posted by  someone claiming to be jparker3 on  Mon Aug 8 03:50 CST 2005 [RELATED]

        Sounds high on the Eagle or is that Aus $. Not at home where I can check easily.
        Better to go to a new thread. I would like to continue discussion of
        "Topi" style stroker. Never quite clear or satisfied with explanation of rod location side to side in journal. My recollection is that the rod is something like .050 narrower than the journal width.

        John
        v-performance.com







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          B20/B21 distributor questions 120-130

          posted by  CyaLater on  Mon Aug 8 05:57 CST 2005
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          Australian money. A set of Crowers are $1445 Australian.

          The Topi style stoker intrigues me because ACL makes some great hypereutectic pistons for the very common here in Australia Mitsubishi 4G54. They start at 91.1mm bore & have compression heights around 36mm. These pistons + 4G63 rods + 89mm stroke = the correct total height after a cleanup skim of the deck.

          Never quite clear or satisfied with explanation of rod location side to side in journal. My recollection is that the rod is something like .050 narrower than the journal width.

          The early 4G63 rod is 1.116" wide which is the same as the 8-Bolt rods IIRC.







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            B20/B21 distributor questions 120-130

            posted by  jparker3 on  Thu Aug 11 13:35 CST 2005
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            last visit: Tue Jun 9 18:47 CST 2009
            [RELATED]

            "The early 4G63 rod is 1.116" wide which is the same as the 8-Bolt rods IIRC."


            I keep thinking of the 6 bolt rod width.
            The Mitsubishi sounds like a reasonable setup in the 8 bolt crank if done right.
            Think I'll try one. ---

            Actually have two done by Topi sitting in the shop right now, including his own 140 rally car. Can't be sure which versions they are unless I pull them part though. He did the strokers several different ways over the years. Some more successfull than others.

            John
            V-performance.com








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              B20/B21 distributor questions 120-130

              posted by  CyaLater on  Thu Aug 11 20:21 CST 2005
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              It's the cheap way to go, but I like the sound of a 92mm stroke fully counterweighted crank. Can you squeak any more stroke out?

              KB have 4G54 cast pistons you would be looking for to go with 4G63 rods.







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                B20/B21 distributor questions 120-130

                posted by  jparker3 on  Fri Aug 12 01:22 CST 2005
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                last visit: Tue Jun 9 18:47 CST 2009
                [RELATED]

                The problems with the custom cranks have been price and delivery time.
                Cranks that were due in May are not here yet and I can't live with that kind of
                scheduling. Obviously there are priorities and not everyone is waiting 6 months.

                In any case, it's nice to have alternatives, so I am going to try a couple of different ways of doing this, especially if we can make more power available to other customers at a lower price and still have good reliability. My concern, though , is keeping reliability. With the Mitsubishi rod journal size and a stroker we are giving up a lot of bearing surface area and gaining a lot of bearing speed. Thanks for the piston info.

                John
                V-performance.com








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    B20/B21 distributor questions 120-130

    posted by  CyaLater on  Tue Aug 2 21:57 CST 2005
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    There's no point putting vacuum advance on a stock B20B or E. That's why they didn't fit it as standard. You *might* get some more MPG with vacuum advance on a D-Jet car if you are prepared to fiddle with the map sensor.







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      Emissions tricks? 120-130

      posted by  mario_e on  Wed Aug 3 02:06 CST 2005
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      last visit: Wed Sep 17 06:43 CST 2008
      [RELATED]

      I've read some recently on the advantages of vacuum advance and its been my impression that a lot of what was going on in the early seventies had to do with passing emission standards than making engines run better.

      The article in the current Classis Motorsports is what got this all started. Better MPG and part throttle performance is exactly what I would like to improve.

      I'm still trying to figure this out, but I'm thinking that with vacuum advance the carb tuning and total advance curve can be adjusted for better overall efficiency.

      Another component seems to be a high energy spark, John Parker seems to be currently thinking that it can help off-idle throttle response. Seems to eliminate lean stumble without having to adjust the carb so much that you get too rich of an air/fuel mixture at cruise.

      In any case I'm still researching.

      -Mario E.








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        Emissions tricks? 120-130

        posted by  CyaLater on  Wed Aug 3 04:31 CST 2005
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        its been my impression that a lot of what was going on in the early seventies had to do with passing emission standards than making engines run better.

        They would have tuned to maximum fuel economy too.

        Another component seems to be a high energy spark, John Parker seems to be currently thinking that it can help off-idle throttle response. Seems to eliminate lean stumble without having to adjust the carb so much that you get too rich of an air/fuel mixture at cruise.

        With a high energy ignition you might get a couple of extra MPG with a vacuum advance, but you also have to provide a weaker part throttle mixture. What sort of induction have you got?

        If you have a stock engine with stock carbs & you also have off-idle stumble, then you need to fix this first before doing anything else.







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          Emissions tricks? 120-130

          posted by  mario_e on  Wed Aug 3 08:04 CST 2005
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          last visit: Wed Sep 17 06:43 CST 2008
          [RELATED]

          I'm running and will be running SU's.

          I don't have off-idle stumble but the advance conversion isn't so much for problem solving as for improving the day-to-day life with technology this old. So if vac advance and high energy spark allows for better carb-tuning at cruise then all the better.

          In the early seventies I thought the focus was on reducing emissions and lean mixtures and timing tricks did this at the cost of performance. If they were trying to increase fuel efficiency wouldn't power per cubic cc have increased? I was watching Sesame Street when this was happening so I don't really know the history.

          I'm afraid I'm not enough of an engine guru to make an informed argument for or against. I'm doing research to see if this vacuum advance is worth trying.

          Dyno and gas analysis would probably be the only way to get real info. and I'm not currently planning on doing either soon. But will have to do at some point as seems the way to best tune carb and ignition timing for a truly happy B20.

          The basis of a lot of this line of thought is the Classic Motorsports article. Worth reading and should only cost a cup of coffee at the bookstore of your choice, not too long of an article. I mention this not to say you need to learn about ignition, just to let you know where I'm coming from.

          As I said I am not enough of an engine guy to be able to make hypotheses about what "should" work.

          I am happy to learn what does work and try to understand why.

          Best regards,

          -Mario E.








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            Emissions tricks? 120-130

            posted by  CyaLater on  Thu Aug 4 20:22 CST 2005
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            The theory is during part throttle cruising you can lean the mixture out a little more if you give your motor some more advance. It just doesn't seem to work on performace versions of B20's. I put this down to great atomization from SU's or injection combined with an an intake port that provides reasonable swirl into the cylinder.

            Vacuum advance would be useful with boosted engines. You could cut back the timing provided with centrifugal advance during boosted suitations & then use vacuum advance to bring the total timing up to normal during part throttle cruising.

            If you want some serious gains in MPG, get one of John Parkers street ported F heads & a free flowing exhaust systems. Best bang for the buck would be his $625 head.(You provide a good F head, he ports it & fits dual springs).







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              Emissions tricks? 120-130

              posted by  someone claiming to be jparker3 on  Mon Aug 8 03:30 CST 2005 [RELATED]

              Thanks for the endorsement.

              Finding that the same thing is true when trying to use the highest CR we can on
              the pump gas now available.

              v.performance.com








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    B20/B21 distributor questions 120-130

    posted by  someone claiming to be Rhys on  Tue Aug 2 14:54 CST 2005 [RELATED]

    Many of the Canadian B21A's had a dual advance-retard vacuum pot. I may have one around, certainly I have the advance ones as well. You can e-mail me from my website at www.sucarburetors.com







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      B20/B21 distributor questions 120-130

      posted by  jparker3 on  Wed Aug 3 12:04 CST 2005
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      last visit: Tue Jun 9 18:47 CST 2009
      [RELATED]

      Well, the question is whether the vacuum units are a bolt-on to convert a B20 vacuum retard dist. to vacuum retard/advance, allowing you to chose either, both, or just vacuum advance.

      John
      V-performance.com








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    B20/B21 distributor questions 120-130

    posted by  jparker3 on  Tue Aug 2 14:09 CST 2005
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    last visit: Tue Jun 9 18:47 CST 2009
    [RELATED]

    Mario,
    I should have added that I thought there was also a B21 turbo with a dist that had Vacuum advance and retard like the Saab, but I never got hold of one to verify
    it and that it would fit, while I had several of the Saab dist. Now I will have to check on the Volvo. If the vacuum unit is $20 new and will work as a swap onto the earlier dist. that's great.

    John
    V-performance.com







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