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Dino Saga 060716___Carb Synch and Idle

Discussion in 'Corbani's Corner' started by John Corbani, Jul 16, 2006.

  1. John Corbani

    John Corbani Formula 3
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    #1 John Corbani, Jul 16, 2006
    Last edited by a moderator: Sep 7, 2017
    Dino Saga 060716___Carb Synch and Idle

    There are tricks to carb synch. Ferrarichat’s Birdman laid it out in detail for a 308. Read it and then try my version for the Dino. I won’t use as many words as he did but he had 4 carbs to play with and went all the way into everything. See birdmanferrari.com

    First trick is to get at the carbs easily. You have to remove the air plenum. The 12 nuts that hold it on the carbs are 8 too many for do-it-yourselfers. I use the four inside ones on the two end carbs. Al plates on end carbs only. Red silicone holds brass spacers to studs.

    Second trick is to provide a single idle stop attached to the motor. A 1/8” thick piece of Al plate, tapped 10-32, with a Pan Head screw and spring goes on the same stud that holds the throttle spring bracket. Screw hits end of ball joint shaft. Idle stop screws on carbs are all backed off. Springs on carb throttles preload linkage. No drift.

    Use a dial type air flow meter. Pith ball in tube is a waste of time. No damping and hard to read. I use 1000 RPM as my idle. You can go down to 750 but things get more difficult and engine dies when idling just after start up or at temp extremes. I have all smog gear gone. If you still have it, good luck. Extra points, microswitch just add grief. If this is your first time on the car, loosen all lock nuts on air balance screws and tighten screws; re-lock gently. Warm car and idle at 1000. Check flow in each barrel. Adjust throttle nuts until all three carbs are close. Then check the match between barrels on each carb. If one barrel is low, unlock that air screw, balance and re-lock. There should be one screw closed on each carb. Two is fine if that is where they balance. This should be a one time adjustment for the life of the car.

    Now fine adjust each carb to the other two. Requires two 10 mm wrenches and someone to hold threaded shaft. Can take some time to get match and have throttle shafts/linkage square. When you think you are done, cycle linkage repeatedly and make sure that nothing is binding. Synch is done and should last a long time. Oil linkage occasionally.

    Final idle requires a CO monitor or a little guessing. Air is balanced, fuel now has to match. Baseline is to run single idle screw in, back out until cylinder fires, then another ½ turn. Adjust throttle stop to keep revs at 1000. Play with a cylinder at a time. Pull a plug lead occasionally to keep yourself honest. Hard to determine exactly when cylinder kicks in. If you have monitor, dial in lowest CO and you are done.

    Good to check synch every year or so; or after a long time in a shop. If car still acts funny after synch, figure idle jets. Just pull and clean them, then reset idle mixture. My carbs have never had anything replaced. Carb air balance is a one time thing as is float level. Wear of throttle linkage and plugging of idle jets are only reoccurring problems.

    If it’s broke, fix it. Keeps the juices flowing and the second time is easy. Drive!

    John
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  3. JTR

    JTR Formula 3
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    Apr 26, 2005
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    Where did you get the flow meter, John?
    I've seen the ball type offered, but never the dial type.
    Thanks, always enjoy your write-ups,
    John
     
  4. John Corbani

    John Corbani Formula 3
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    Buddy in Germany gave it to me. He raced small formula cars and Group C. Had it in his goody box. It is marked:

    mehrvergaser
    synchron tester
    Made in West Germany

    Scale goes from 4 to 40 with a little 400 at the 4 end of the scale. Dino idles about 10 whatever that is. The base has 2 bypass holes that can be opened to extend the range upward. JC Whitney sold the same thing for $29.95 in a 2002 catalog. Probably still does. Best investment you will ever make.

    John
     
  5. J.P.Sarti

    J.P.Sarti Guest

    May 23, 2005
    2,406
    any flat spots through the rpm band John?
     
  6. John Corbani

    John Corbani Formula 3
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    Most fun in the world is to go from 2000 to 7000 in fourth gear. Or fifth. No flat spots. Just builds to a kick going through 3500 then torque holds as noise builds. No hesitation either when accelerating from a steady 3000. Advance is a big part of that. But carbs have to be right too.

    John
     
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  8. need4speed

    need4speed Formula 3

    Nov 3, 2003
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    Awesome John. Thanks,

    Manny
     
  9. Birdman

    Birdman F1 Veteran

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    Good write-up John, even though your pics are over-sharpened. ;)

    I would be worried about air (and therefore dust) sneaking around the bottom of the carbs without all 12 nuts though. But then again, I don't have a Dino and I have never tinkered with them, so my opinion is worth squat there.

    I'm a little confused on the idle stop mod. Why did you do this?

    FYI, You can get a good synchrometer here for $40:

    http://www.webercarbsdirect.com/inc/pdetail?v=1&pid=794
     
  10. John Corbani

    John Corbani Formula 3
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    If you don't, one of the carbs becomes the idle stop. It is always the wrong one. And that one gets pounded by the strong return spring. And wears. And that throttle actuating shaft takes a beating, and the arm on the threaded rod gets an elongated hole. And another carb becomes the stop. And synch goes to Hell.

    Separate stop is strong and is steel against steel. Takes the return spring force nicely. Each carb has a spring on the throttle shaft and that spring just takes the slop out of the mechanism. Leaves very low force on all 3 carb shafts. A drop of motor oil every year or so keeps things good.

    Virtually no leakage between carbs and air box. Rubber gaskets still touch. 34 years and 188,000 miles is a pretty good test. If I was going to try a 24 hour road race I would use all nuts. Highway driving only needs 4.

    John
     
  11. dignini

    dignini Formula 3

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    John, you lost the other eight nuts didn't you :)
    Excellent post, having good sparks really helps too.
     
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  13. John Corbani

    John Corbani Formula 3
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    Nope! You should see my goodie box.

    John
     
  14. Birdman

    Birdman F1 Veteran

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    Sounds like a crappy design and a good opportunity for you to build a Dino Idle retrofit kit!

    Birdman
     
  15. need4speed

    need4speed Formula 3

    Nov 3, 2003
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    I second the idea of a Dino idle kit! :)
     
  16. BillyD

    BillyD Formula 3
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    Hey John,
    Beautiful Dino & thanks for info, uh how fast is 7k in 4th gear. ;-)
    Bill
     
  17. John Corbani

    John Corbani Formula 3
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    About 131. gets there pretty quick. Takes a long time from there on up but I have no doubt it will meet specs if you have a long road and a cool day. Gets smoother as speed builds and stays firm. It's set up a little nose down. I've had it over 140 and still accelerating. Ran out of road. Book says 148 at 7800. Very much the same feeling as flying a light airplane very low.

    John
     
  18. celestialcoop

    celestialcoop Formula Junior
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    1st post of many, this!

    Interesting read, John. Your 'Dino Saga' series is always well-received. Thanks!

    Greetings to all fellow Weber operators,
    Here are a few more sources for flow meters--from mild to wild. The first gauge appears to be similar to the one John uses. As he said, JC Whitney.

    Schleyer Carb Synchronizer $29.95 http://www.jcwhitney.com/autoparts/Product/tf-Browse/s-10101/Pr-p_Product.CATENTRY_ID:2008076/p-2008076/N-111+10201+600003570/c-10101

    The next three vendors sell a different meter. Anyone tried it?

    Bugpack Carb Synchrometer $79.95
    http://www.jcwhitney.com/autoparts/Product/tf-Browse/s-10101/Pr-p_Product.CATENTRY_ID:2004219/p-2004219/N-111+10201+600003570/c-10101

    Synchrometer (Same for less?) $39.95
    http://www.webercarbsdirect.com/tuning_aids1

    EMPI Synchrometer (Same as previous two? Best price!) $29.00
    EBAY Item Number 150012848957

    Lastly, expensive tuning aids for Webers (Synchrometer for $79.95, but check out the more sophisticated stuff!)
    This supplier also sells a DCNF adaptor (STE 18) for $14.95. http://www.webercarburetor.com/accessories.htm


    I'm to the garage to fabricate!
    Cheers...
    Coop
     
  19. celestialcoop

    celestialcoop Formula Junior
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    I opted for the EMPI UNIVERSAL CARB SYNC. When it arrived I discovered that their 'Syncrometer' is made in Taiwan and appears to be a plastic knock-off of the original German-made Synchrometer. I don't know how accurate this one is; it might be dead-on, for all I know! That being said, it should serve our purpose as it only has to compare - not calibrate - the air flow. It'll also be interesting to see if it fits the DCNF carb with the supplied standard adapters, as the instruction sheet refers to HPMX and IDF carbs for Porsche and VW applications.
    I'll have another update later.
     
  20. DinoDriver

    DinoDriver Formula Junior

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    I've used the German made Synchrometer STE SK ($39.95), as noted above by celestialcoop, for many years -- excellent quality, large easily viewed scale and minimal "jitter" on the dial bug. Sure beats the ol' Uni-Syn. Anybody remember those?

    Bill
     
  21. celestialcoop

    celestialcoop Formula Junior
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    Bill,
    Is your proper German-built Synchrometer made of metal? I didn't notice the spelling variant before ordering my 'Syncrometer' from EMPI. I was surprised by the plastic construction, but now it all makes sense. I imagine the additional ten bucks would have been well spent for the real deal. We'll see. Do you use yours with the STE 18 DCNF adaptor I mentioned, or does the standard conical piece work fine?
    I have a vintage Uni-Syn, too. I've used it over the years on twin SU carbs with a reasonable degree of success (ignorance is bliss). However, this newer design should be more user-friendly on the Dino.
    Cheers,
    Stephen
     
  22. DinoDriver

    DinoDriver Formula Junior

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    Stephen,

    The "real" german item is also plastic. Looks just like yours. As you said in your post, it's for comparison measurement, not flow measurement so you are fine. I'm not using any kind of an adaptor with mine for the Dino. It is SOOO much better than the Uni-Syn!

    Bill
     
  23. synchro

    synchro F1 Veteran

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    Only 130 indicated on my speedo - Northbound 101 just past Paso Robles Aug 2004 on the way to Monterey.

    I yield to John's testing as conclusively superior data.
     
  24. need4speed

    need4speed Formula 3

    Nov 3, 2003
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    My speedo read 155 @ 7500rpm @ 1AM on the 101N just past Solvang. :)

    I knew it was optimistic but it felt so good. So good in fact that I kept her there for about 20 minutes. I had a companion for a time, an Alfa Romeo Montreal. He dropped back after my speedo passed 140. :)
     
  25. synchro

    synchro F1 Veteran

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    Which gear?


    These are delightful engines, aren't they?

     
  26. need4speed

    need4speed Formula 3

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    5th gear.

    And yes, the engine is very sweet indeed.
     
  27. sulzeruk

    sulzeruk Karting

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    #24 sulzeruk, Aug 24, 2006
    Last edited by a moderator: Sep 7, 2017
    Hi all, I was sent this by Mike at Superformance. I tried it out on the good Dino tonight and it worke quited well. I think I have a blocked idle passage as I could not get the engine running at idle on all 6. It would sort of chunter, I don't know if it has anything to do with the big valves and different cams in the engine. i should really tear them down and check. i also noticed that there was some fuel dribbling out of the accelerator pump jets when the engine was idling, this was only on the centre carb though, possibly a split diaphragm? More work!!
    Al Cowan
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  28. John Corbani

    John Corbani Formula 3
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    Alasdair,

    I think my way and Birdman's way will get you there much faster and the car will idle better. Opening the air bypass screws one turn is the problem. That air does not flow across the idle jets and funny things happen. I believe that those should be closed as much as possible to get best atomization of fuel. Try it both ways and let us know which is better. Also, the independant idle adjustments are a pain, that is why the master idle stop.

    Good luck,

    John
     

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