Float adjustment by needle-valve shimming works well for carbed Boxers! | FerrariChat

Float adjustment by needle-valve shimming works well for carbed Boxers!

Discussion in 'Boxers/TR/M' started by dr.mike, Dec 1, 2007.

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  1. dr.mike

    dr.mike Karting

    Oct 31, 2003
    153
    Laguna Hills, CA
    Full Name:
    Mike Adams
    #1 dr.mike, Dec 1, 2007
    As planned, I adjusted the float height on my carbs by installing shim washers under the needle-valves. I increased the float height by 2mm. This completely cleared up the acceleration hole. I will get some RPM/AFR traces with the LM-1 next week. Todays driving/tuning session was rained out :( But that may have been for the best, as my knees and back were killing me from the previous day's driving. Offsetting the pedals may be next!

    1st I measured the running float hight on all of the bowls with a straw down the float vent. Actually it was the little spray tube that comes with a can of WD-40. Even though the floats were set up with the Weber tool specifically for this application, the measured running float heights varied by more than 1mm from bowl to bowl. So, I equalized everything while raising the average level using the shims.

    Because of the pivot/fulcrum arrangement of the float/needle-valve, a 1.0mm shim gave 4mm of additional float height. So the 1mm shims are not so useful. I used a combination of 0.1mm and 0.2mm shims to bring everything to where I wanted it. Now I know that i need 58mm from the top of the float to the top of the vent tube.

    If anyone is interested, I got the shim washers from McMaster Carr. Parts numbers below:

    1 98089A385 Metric 18-8 Stainless Steel Shim 1.0mm Thick, 10mm ID, 16mm OD, Packs of 50 $10.61
    2 98089A255 Metric 18-8 Stainless Steel Shim 0.2mm Thick, 10mm ID, 16mm OD, Packs of 50 $10.82
    3 98089A216 Metric 18-8 Stainless Steel Shim 0.1mm Thick, 10mm ID, 16mm OD, Packs of 50 $9.75

    But I can sell you a special "Ferrari 12 cylinder float tuning kit" of the same for, say, $400.00 if it makes you feel better ;) STRAW INCLUDED! I keep the WD-40

    The main circuit now seems to come on about 800RPM earlier. The idle circuit was mostly unaffected.

    This was very easy and went quickly. Especially compared to doing it the "right" way :)
    With the air boxes removed, The needle valves are easily accessible from the top of the carb.

    Now If I can just find a driving position in the boxer that wont put me into a wheelchair at an early age!
     
  2. 246tasman

    246tasman Formula 3

    Jun 21, 2007
    1,441
    UK
    Full Name:
    Will Tomkins
    #2 246tasman, Dec 1, 2007
    nice idea! Thanks
     
  3. JTR

    JTR Formula 3
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    Apr 26, 2005
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    #3 JTR, Dec 3, 2007
    Thanks for taking the time to post this Mike!
    I don’t know how I missed it, but possibly because work is interfering with my F-Chat time.
    So, by equalizing the float levels, then raising them 2mm above the stock setting, the flat spot has vanished?
    Did you adjust the float level with the engine running, or just with the fuel pumps running?
    Is the 58mm measurement, top of float to top of vent tube, the final height?
    If your adjustments still seems to be working okay after your next test drive, I’ll give it a try on my car.
    I love the carbs, but the flat spot can be annoying.
    Sorry about you discomfort while driving. Perhaps you haven’t assumed the proper Italian slouch driving position yet; seat back, seat back tilted back, arms barely reaching the steering wheel, eyes peering just over the top of the wheel. Very comfortable once you get used to it. Sort of the same position the low rider/gangsta guys drive their fartcan equipped Honda’s.
    John
     
  4. JTR

    JTR Formula 3
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    #4 JTR, Dec 17, 2007
    Should read 'Did you CHECK the float level with the engine running,,,,,,,,'
     
  5. dr.mike

    dr.mike Karting

    Oct 31, 2003
    153
    Laguna Hills, CA
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    Mike Adams
    #5 dr.mike, Dec 18, 2007
    Perhaps some fuzzy dice would help :p
     
  6. fastradio

    fastradio F1 Rookie
    BANNED Professional Ferrari Technician

    Apr 26, 2006
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    David Feinberg
    #6 fastradio, Sep 4, 2008
    Dr. Mike,

    I just completed this modification on my 365bb. It really made a dramatic improvement in driveability, with the only downside being a required slight tweak to the idle/slow speed mixture (a bit leaner)...I've got to agree with you 100% that adding the shims to raise the float height sure beats the ever so tedious "Weber method". Thanks so much for this highly effective tech tip. I took her for a 125 mile test drive last weekend and was delighted with the new feel of the car...


    Regards,
    David
     
  7. 512bbnevada

    512bbnevada Formula Junior
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    Biff
    #7 512bbnevada, Sep 4, 2008
    The sight glass used for 911s works well instead of a straw
     
  8. dr.mike

    dr.mike Karting

    Oct 31, 2003
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    Mike Adams
    #8 dr.mike, Sep 4, 2008
    Glad someone else found it useful, David.


    I'm way too cheap for that :p
     
  9. fastradio

    fastradio F1 Rookie
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    #9 fastradio, Sep 4, 2008

    I have this tool and although useful, I perceive better resolution with the straw. Also, raising the float levels by using shims, versus bending the float tabs, is a huge time saver...and I can actually get all the floats at the same, exact height.

    Long and short, she really sings now and is even more of a blast to drive than ever before!


    David
     
  10. 512bbnevada

    512bbnevada Formula Junior
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    #10 512bbnevada, Sep 4, 2008
    Where do you insert the straw exactly? Interesting porsche has a 13mm height but Ferrari wanted a 15mm height I believe each Weber on both cars service almost the same displacement size pistons
     
  11. dr.mike

    dr.mike Karting

    Oct 31, 2003
    153
    Laguna Hills, CA
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    Mike Adams
    #11 dr.mike, Sep 4, 2008
    You drop the straw down the float vent tube. It is right over the center of the float.
     
  12. JTR

    JTR Formula 3
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    Apr 26, 2005
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    #12 JTR, Sep 5, 2008
    Thanks again Dr Mike,
    and I'll give it a try on my car just as soon as I'm back home again.
    John
     

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