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308 carb removal

Discussion in 'Technical Q&A' started by Mike328, Dec 8, 2003.

  1. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    I'm having Pierce Manifolds rebuild my carburettors on my 78 308. (They've got an "appointment" in mid-December!)

    Does anybody have any information on what it takes to completely extract the carbs out, but keep them together as complete units?

    I've got it down to removal of the air cleaner and carb horns... And from there? Things to watch out for?
     
  2. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,339
    B.C., Canada
    Nothing special. Just make sure you mark where the the threaded rod-links go (even though they both have R & LH threads, one is longer than the other) and that's about it. Write down which carb# goes where (remember they're identified. eg: 40DCNF45, 40DCNF46, 40DCNF47, etc... Yours are probably different numbers but in any case, its the last two).

    I find it difficult to undo the nuts that are under the float bowl area, so be patient with those (stubby wrenches will be a big help). You'll find that as you reach the end of the stud, the nut will jam against the float bowl, so you'll have to pull up on the carb to make clerance... Don't drop the nuts afterwards when they come off the studs!
     
  3. pma1010

    pma1010 F1 Rookie
    Silver Subscribed

    Jul 21, 2002
    2,556
    Chicago
    Full Name:
    Philip
    Peter
    In general, how smooth were the intake manifold runners when you pulled the carbs? Do you think a fine hone or some careful port matching would improve flow? Caribou found a 7 BHP gain from the ex port - manifold matching.
    Philip
     
  4. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
    1,606
    colorado
    Full Name:
    Giovanni Pasquale
    Hello Mike
    I have had my carbs off twice now, take a good digital pic of the setup - its worth a thousand words. Just be careful not to drop anything down the intake runners. its all pretty straight forward in the removal, i know there is a sequence to which carbs get removed / replaced, but its been a while. the sequence just makes getting to the carb holddown nuts easier. take good pics of teh linkage.
    john
     
  5. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    I removed the left side carbs first, nearest to the oil filter. Then it made it easy to get the others off. I video taped mine just to show how to do it. I pulled out the clevis pin and unscrewed the fitting to remove the linkages from the carbs.
     
  6. yelcab

    yelcab F1 Veteran
    Consultant

    Nov 29, 2001
    9,056
    San Carlos, CA
    Full Name:
    Mitchell Le
    The sequence is essentially the most difficult nut to remove goes back on first. That is because you need to install the nut while holding the carbs up by 1/4 inch so the nut will clear the fuel bowel. If you install the other nuts first, there is no room to lift up on the carbs
     
  7. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,339
    B.C., Canada
    Nicely finished actually, I'd guess maybe done with 80 or 120 grit, thereabouts. Matching was bad, both of manifold and the gasket stuck out in a few places too. Definite improvement could be made there, keep an eye out for it.
     
  8. ants2au

    ants2au Formula Junior

    Nov 19, 2003
    690
    Sydney Australia
    Full Name:
    Anthony

    I am actually doing my carbs at the moment on my 308, and I have found the following:
    The intake runners were too smooth for proper fuel mixing (maybe that's original, or maybe someone got to it before me).

    The port matching from carb to manifold, and manifold to head, were off only on one side of the port diameter (how odd, they match on one half of the circle, and off on the other).

    So my plan is to match the port on the carb/manifold side, but taking some metal of the manifold opening.
    As to the manifold/head side, I am abit conserned taking metal of the head side, as I want the port flow to go from large to small as it gets to the valve opening.

    Does anyone have any opinion on this?
    I want to keep the flow diameter the same (ie large to small to keep the are velocity increasing), but want to get rid of the ridge in the flow path that is the manifold/head interface.

    Also I will be finishing off the port walls with 40 grit, as the intake runners are so short, it needs all the mixing it can get
     
  9. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    Help! Just need one more thing and I'm GOLDEN!

    Last night I removed the air cleaner (my first time!) without any issues.

    Tonight, I got most of the nuts removed from the carbs where it attaches to the manifold... Doing well. I've also removed the fuel lines and choke linkages.

    I finally got four nuts off the front left carb (drivers side, towards the front of the car).

    I can't get the carb off because of some complex (to me) throttle linkage stuff going on... I can't figure out how to remove it.

    Can somebody clue me in on how to do this?

    I see a cylindrical assembly with a threaded shaft coming out of it. There is a strange, small cotter-pin like wire at the end of the cylinder. There is an 8mm nut against the cylinder on the end of one of the threaded shafts, which I loosened. I don't know where to go from here...

    Thanks guys,

    --Mike
     
  10. ants2au

    ants2au Formula Junior

    Nov 19, 2003
    690
    Sydney Australia
    Full Name:
    Anthony

    You have to pull the small cotter pin out, and using a screwdriver, unscrew the big "grub" screw that was being held by the cotter pin. Once you do that, the shaft with the nut on it that has cylindrical assembly, has a ball that fits into it, which will then pop out.

    voila, disconnected.
     
  11. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    Thanks very much... About to go finish the job now.
     

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