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Final word on 78 308 carb float heights?

Discussion in 'Technical Q&A' started by Mike328, Jan 25, 2004.

  1. Mike328

    Mike328 F1 Rookie
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    Oct 19, 2002
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    Mike
    I've done a lot of research regarding float heights on 308 carbs and just wanted to see if there was an expert consensus.

    78 308 owners manual indicates float heights at 48mm to 58.5mm (a 10.5mm swing between open and closed).

    Is there a valid reason to set the float heights higher, to say 46mm?
     
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  3. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
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    Hans E. Hansen
    Some are setting them higher to try and alleve fuel starvation in corners. Don't know if it works, but it does open up a different can-o-worms as it will influence fuel mixture. Too high, and it will seep out thru the aux venturies at low rpm, or even with the engine not running.

    I did find several different references in float setting. There seems to be a 50 .vs. 48mm thing - altho I only saw one reference to 50. Also, I saw a reference that said to have the gasket in place - again, only one reference. Also, there is the issue as to whether to include the solder seam in the measurement, or measure the other, "cleaner" side. Upon reflection, I think the 50mm reference was measuring with the seam. That would probably be similar to 48mm w/o seam. I'll have to look for that reference.

    Anyway, the concensus seems to be to measure 48mm gasketless, non-seam side. At least that's what I do.
     
  4. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    From experience IMO stay with the 50mm form the gasket.
    Iv'e use this sucessfully in the past.
    HTH
    Kermit
     
  5. ferrarifixer

    ferrarifixer F1 Veteran
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    Jul 22, 2003
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    The lower reading, or higher measurement is at least equally as important, and many seem to ignore it.

    If the float is not allowed to drop fully, the bowl won't fill fully, so go to both extremes without just going for the max level.

    It amazes me how many are not set correctly.

    One of my customers with a near std 308 just raced around Winton (as a prologue for a rally stage), which has notoriously long sweeping corners, known for causing oil/float dramas. He has extra grippy 16" tyres fitted too. He suffered no oil surge or float level dramas at all. The float levels are accurately set to std, and the oil is overfilled to 200mm over max when hot, on his wet sump engine.

    These cars are so often poorly set up that they get a bad reputation for the wrong reason.

    I'm not saying they're perfect, but they so often be so much better than they are.
     
  6. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
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    There are two settings for the 308 -

    48mm for the twin distributor car
    50mm for the single distributor car

    However depending on the type of use these figures can be altered by a few milimetres (ie. track use where excessive high speed cornering is used )

    These figures are without the gasket.


    MW
     
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  8. ferrarifixer

    ferrarifixer F1 Veteran
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    I go 48mm on all as my std interpretation of the info.

    By the way, the oil is 20mm over max, not 200mm......oops sorry
     
  9. jmillard308

    jmillard308 F1 Veteran
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    May 29, 2003
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    Gee thanks Phil!
    I have just finished cleaning the excess oil off the carpet after I tried to overfill by 200mm :)
    LOL
     
  10. ferrarifixer

    ferrarifixer F1 Veteran
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    serves you right for having carpet in your garage, or your car in your lounge.......either is truly obsessive!
     
  11. bill308

    bill308 Formula 3
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    May 13, 2001
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    Bill Sebestyen
    The 1975 GT-4, North American version, is fitted with 2-distributors and 40DCNF4x series carbs. Float level on these carbs is 50 mm from the cover surface, (no gasket) per the OM.

    Float droop should not exceed 58.5 mm. The sin here is to allow droop to exceed 58.5 mm as there is a danger the needle valve will not close upon filling the bowl to the proper height due to geometry considerations. A little less is probably ok, at worst, affecting only the rate at which the float chamber will be refilled. Obviously if the droop is equal to the closing height of 48 or 50 mm, the float chamber should not fill at all.
     
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  13. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
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    Hmmm......

    All of the manuals that came with my 1975 say 48mm.
     
  14. bill308

    bill308 Formula 3
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  15. Peter

    Peter F1 Veteran
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    Dec 21, 2000
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    True. U.S. GT4's call for 50mm height (in my original OM). I've got the droop set at 58.5 (true for all models I believe, not specified in the OM).
     

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