NON CAT carbed Jet Selection discussion.... | FerrariChat
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NON CAT carbed Jet Selection discussion....

Discussion in '308/328' started by BigTex, Apr 11, 2025.

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  1. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    Bubba
    #1 BigTex, Apr 11, 2025
    Last edited: Apr 11, 2025
    So, it's been a LONG time since our cars were made, and fuel profiles are certainly different.

    My 1977 has gone down from ethanol fuel contamination (my bad, lesson learned) but "while they are in there" I made special point to have the Emulsion Tube and jet selections confirmed (Do they even MATCH?? :D :D ) and changed to WHAT, exactly??

    I'm sure "somewhere in my stuff:" I have the very informative Chart of Original jet sizes.
    Across all the worldwide markets...

    But what should the jets (and or Tubes) be changed to for today's (usually Shell) fuel?

    My shop has accused me of neglecting maintenance!!

    "No, man! JRV timed the belts and tuned the engine with ColorTune spark plugs! It passed emissions until it went exempt!" RIP JRV....

    "Then Ferda rebuilt all the carbs, it took him THREE years, and I picked it up just before he destroyed the F40!"
    I think he's passed away also, since Vintage Motorcars folded on West Kempwood....RIP Ferda

    The last person to touch the car was Vintage Motorcar Solutions, (now part of the Alara Storage complex group.) He solved an intake manifold leak, and it ran well (if a litttle rich, reading the spark plugs) and it came back with the Choke Cable disconnected and the mirror knocked off the glass, base mount and all!!

    A friend suggested I could buy some guitar strings and clean the old jets out from the varnished fuel, but am I right in thinking they could be resized to more optimal??

    Stock carb set, stock distrubutors, stock Baldwin filtters, I did change the fuell pump and spark plugs before towing it away.

    Thanks in advance.
    I've missed all of you!!
     
  2. BigTex

    BigTex Seven Time F1 World Champ
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    #2 BigTex, Apr 11, 2025
    Mods, if the answer is buried somewhere in our Section feel free to merge, but I'm really asking against 2025 fuel mixtures.

    Today's news!!!!!
     
  3. JCR

    JCR F1 World Champ
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    #3 JCR, Apr 11, 2025
    Gasoline composition has changed since unleaded in 1974. Over the last couple of decades the aromatics (BTX) portion of gasolines has been reduced. Then there is also the addition of ethanol (oxygenate). This was done first in the USA and Europe has followed. Even since the 1970s the OEMs leaned out the carburetors on all vehicles from new. So with these new gasolines blends, you need to richen up the mixture from both the original (lean) tuning and with the new fuel blends that burn leaner than before.

    Before making any changes make sure you are to factory specs so you can baseline from there.
     
    BigTex likes this.
  4. Ferraripilot

    Ferraripilot F1 World Champ
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    #4 Ferraripilot, Apr 13, 2025
    Stock size idle jet is usually fine, but definitely bump to a 140 main, 200 air corrector (I’ve seen 190s demanded too but that was oh the dyno, 200 is safe). I’ve seen 12hp at the wheels picked up just making this change. It’s noticeable
     
  5. LE06

    LE06 Karting
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    #5 LE06, Apr 13, 2025
    Timely thread sense I am about to rebuild my carbs. Would the jets be the same on a 78 Euro motor?
     
  6. Ferraripilot

    Ferraripilot F1 World Champ
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    #6 Ferraripilot, Apr 14, 2025
    So the Euro engines sometimes have F24 emulsion tubes and different main and air corrector jets but the cams in the Euro cars are the same as the US 76-77 cars. F36 emulsion tubes with 140 mains and 200 air corrector (or even 190) work great. I have always landed right there with these in otherwise stock configuration.
     
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  7. BigTex

    BigTex Seven Time F1 World Champ
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    #7 BigTex, Apr 16, 2025
    I believe that is true...thanks so much guys......I'm entrusted it to someone who probably "already knows" I'm just trying to stay in the conversation over it!!
     

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