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Professional 308 carb rebuild -- Weber DCNF 40s

Discussion in 'Technical Q&A' started by Mike328, Nov 5, 2003.

  1. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    Mike
    Wanted to get some thoughts on pricing for carb rebuilds, as well as things to watch out for in particular.

    At just shy of 60k, I've decided to rebuild the carbs on my 78 308 this winter. I've read a lot on the subject, and understand that older carbs can be full of vacuum leaks (not just as a result of age, but just as a result of the way these particular carbs were cast).

    I got one quote from a very reputable carb place that many FChatters use, to completely tear down and rebuild all four carbs at $200 per carb, $800 for the job (assuming there's no exceptional circumstances regarding the condition of the carbuerettors).

    Does that sound about right?

    The same place quoted around $450 for a new DCNF 40, though commented that the rebuilt ones were as good as the new ones. This price is much less expensive than those I've seen listed on eBay (over $1000? Is that right? I'm a little vague on the price--it was high).

    Now, I thought about doing the rebuild myself, after reading John Asselta's excellent article here:
    http://www.fca-se.org/carbs/

    However, I've never done it before, and just lack the perspective and experience to really to it right. It's too important to chance, and at $800 all together, I think the rebuild is the way to go.

    What are some things in particular I should have done to the carbs? I know they tear them all down, use a sonic cleaner (not solvent) against the carb body (sometimes using "shells" if necessary). If they've been bent or are otherwise out of shape, they'll reshape them... And of course, all parts except "calibrated parts" are replaced--I assume this means the typical wear items.

    Anything else I should watch out for? What else should I explicitly asked be checked / looked at / performed when rebuilding?

    Thanks very much for the help...

    --Mike
     
  2. Glassman

    Glassman F1 World Champ
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    Apr 23, 2002
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    I don't think the price quote is out of line at all. Personally I would leave carb work to a professional, I just don't have the experience to do it right. And there is nothing nicer than getting your carbs back putting them on the car, and it actually starts and runs!
    I used the preferred rebuilders on a 250 GT three carb rebuild. They charged me $800.00 and had to turn one carb from a 40DCL to a 36DCL. I think it was a steal!
     
  3. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Just bought 4 new 40dcnfs at $225 for each.

    They are pretty straightforward - if you have the time, might want to look at a manual to see if you wanted to do it.

    best
    rt
     
  4. Spasso

    Spasso F1 World Champ
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    Hi Mike,
    One thing I found to watch for when rebuilding the Weber DCOE's for my 240 is throttle shaft play. The bushings in the carb body wear out and cause vacuum leaks which makes syncronization nearly impossible and eliminates a consistant and stable tune. This is where the horror stories are born when talking about multiple carbed cars.

    When people see the three dueces on my 240 I am asked numerous times, "How often do you have to resyncronize and tune the carbs?"
    The answer is, "I don't", not in 15,000 miles.....tight throttle shafts.
    Just minor adjustments to the idle mix.


    Russ,
    Four NEW for 225.00 EA.? At a price like that I would jump for four new carbs!. Any left? ;-)

    DJ
     
  5. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    I know--that really is a great deal for new carbs! That said, my feeling was that the rebuilt carbs may have actually done work towards correcting fundamental manufature flaws in carbs themselves (like the castings not sealing and creating vacuum leaks).

    Regarding the work throttle shafts, I'm not sure if this is the same thing, but the person I spoke with talked at great lengths about the "Bearings" (I'm thinking--bearings on a carburettor?). Yes indeed, apparently the bearings are simply exposed, and do get worn in time from the elements... He mentioned that when they rebuild them, the bearings are get sealed.

    Very good to hear that the rebuild price is in line.

    I really feel that $225 for original Weber DCNF 40s is ridiculously low.

    Question: Was ANYTHING done differently to a "stock" Weber DCNF40 when fit to a 308? Were any modifications made?
     
  6. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    The new dcnfs were a good price, and I had aggressively shopped around. A more common price I found was about $400, although folks really would make deals if you bought in multiples. The saga of their protracted delivery from GT Car Parts is documented in the 3.2 Weber conversion thread (with pics) on the old dearly beloved board. Not sure if Bill at GT would duplicate the price again or not.
    The Weber 40 dcnf mounting seems to be the same for all dcnfs from my research. There is a slight construction difference between 4 bolt and 5 bolt top cover mounting, but does not effect other than appearance that I can tell. Someone else may know better. As far as internals: all the jets, tubes and stuff are interchangable and cheap which is why Webers are so great to easily specifically tune.
    The rebuild sounds good if you had an expert completely go through them and replace the bearings.
    best
    rt
     
  7. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Russ Turner
    OBTW
    Mike - suggests in your profile you have a 308 luggage set. Very cool. Did it come with the car or did you get those afterwards? If so, from whom and what should one pay?
    Many thanks
    Russ
     
  8. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
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    To me that is extremely high. It isn't too difficult to rebuild them. Someone posted pics of their rebuild on the old site. I got my kits from Italy for $10 each so for $40 it was well worth it.
     
  9. Spasso

    Spasso F1 World Champ
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    Another note on throttle shaft play and resulting vacuum leaks.

    I heard of a common fix as a backup to preventing the leaks. Once the carbs are rebuilt some of the guys put press fit plugs in the recess surrounding the end of the throttle shafts thus preventing any future leaks. Not a bad idea!

    Maybe this is what the rebuilders are referring to when talking of 'sealing' the bearings.

    DJ
     
  10. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
    1,606
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    Giovanni Pasquale
    HI Mike
    the first time i rebuilt my carbs, i had them sonically cleaned, but this process seemed to disturb the small lead casting plugs and they all started to leak, hence , i rebuilt them again with genuine weber parts, and used seal-all on the casting plugs (there are like 20 plugs on each carb - inside and out). there are no more leaks now. if you can buy the new webers for $250 - go for it, i dont know where they were had for that ammount - . the throttle shafts on my webers were tight, but i would go for a new set of carbs anyday for $250 each - where were they bought??. anyway, $200 each for a rebuild is a good deal - if and only if they use genuine weber parts in the process. hope this helps.
    john
    78 308 GTS Euro
     
  11. pcelenta

    pcelenta Karting

    Nov 1, 2003
    216
    I agree with SNJ5...if they are going to replace the bearings...the price isn't bad...if they are just slapping new grease in them that's a different story....If they are just doing a reseal job then the price is ridiculous...I bought my rebuild kits from Rutlands for $40 each (including base gaskets)...it was really quite simple to reseal them...When I asked Rutlands about float replacement..they said check them...however, they rarely go. the only thing I am working on sorting out now is the PITA 3500 rpm poping...this weekend I dramatically reduced it by replacing all fuel line from the pump to the carbs with 8mm fuel line..it had been 7mm.
     
  12. JIMBO

    JIMBO Formula Junior
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    Oct 31, 2003
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    Russ:
    I just read recently that Ferrari/Shedoni is re-releasing the 308 luggage sets with plans to offer other lines in the future. I'll try to find where I read this... any help?
    Jim
     
  13. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    Bubba
    On the luggage (Thread Hijack!)

    Ferrari Owner's site.

    3,800.00 Euro YeeeeHaaaa!

    TTFN


    Speedy308 for President!
     
  14. JIMBO

    JIMBO Formula Junior
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    Oct 31, 2003
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    OK, I found it in the ferrari owners club E-mail bulletin
    (see www.newsletter@owners.ferrari.com) :

    Fitted luggage sets for classic Ferraris! - In collaboration with Schedoni, Ferrari’s traditional leather supplier, we have commissioned the remanufacture of a number of tailor-made luggage sets for your classic Ferrari. The first fitted luggage in the series – a four-piece set for the 308 GTB and GTS series – is already on-line and will be followed by new releases. Watch this space!
     
  15. yelcab

    yelcab F1 Veteran
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    Nov 29, 2001
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    Thread restored.

    On the rebuild, do it yourself. It is straight forward and with a book or two, you'll get it. No special tools are required unless your carbs shafts and housing is totally screwed up. Compressed air will help. It took me 3 hours for the first one, 1.5 hours for the 2nd one, and 1 hour for each 3rd and 4th.

    1. It is not always necessary to redo bushings, bearing. You do have to check them carefully. The professional rebuild don't include these extra work, I bet.
    2. It is always necessary to change the gaskets, inlet-valves,

    3. It is not a sure thing that you can install 4 rebuilt carburetors and fire up the eninge and it wil ... run. It needs synching up .

    4. Synchronyzation of your four fresh carbs is probably going to take more time than rebuilding them. That took me ... two days (with a air meter, timing light (2) and tachometer) and the encouragement from the board. Oh, I miss Ed Gault.
     
  16. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    yelcab,

    Impressive that you were able to rebuild your carbs so quickly.

    I'm just not confident that I can do it right. This coming from an engineer with some big balls. I know this needs to be done right, and I'm thinking that nobody is going to be able to do these like guys who rebuild them every day.

    That said, if it only took you 1 hour in the end to do a carb, I'm not sure if you're doing them correctly... Did you completely tear down the carburetor--down to the last component? Did you clean them sonically or with solvents?

    I agree about the car not starting up--I expect to have to completely resync the carbs. That said, it seems like syncing up the carbs will be an easier deal after the rebuild.

    Question: If I'm also putting on the an electromotive ignition, should I rebuild the carbs BEFORE, or after? I'm thinking before hand, and put them back on with the mechanical ignition (get them resynced), then the Electromotive...
     
  17. yelcab

    yelcab F1 Veteran
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    Nov 29, 2001
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    The first one took long because I had to figure out how to remove every little thing. Then it got easier once you do one.

    I disasseble everything down, except I did not remove the shaft from the butterfly. They were in good shape, did not leak, did not feel loose, and did not have a scored mark inside the venturies so I left them alone.

    I did soak all the components in a carb cleaner tank for a while. I did not count the time the things sit inside the tank, because ... I did not do anything there. Reassembly was straight forward, adjusting the floats was not long. Everything else went back together in a snap.

    I used compressed air to blow out everything, used solvent and brake parts cleaner to clean out all the metal parts if they are gunked up. I think I lucked out because my carbs were in pretty good shape and not abused so I did not take extremely long to rebuild. It would have been alot longer to do if the shafts had to come out, the bearings replaced.

    Synching up was harder, but once they are in synch, they stay put and run just fine now. It has been a whole year, no issues.
     
  18. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,339
    B.C., Canada
    All great advice in this thread.

    I'll stress DJ's comments about leaks around the throttle shafts, since I suffered from this once and it drove me nuts trying to find out why it was driving like crap. Using my stethoscope, I discovered the "hissing" right from the housing of throttle bearings. A little bit of thick grease and some thin teflon washers (home made) and no problems since.

    Be very careful when removing those throttle plates (if you need to. Otherwise don't). Grind the exposed, threaded end of the screws first before turning them out. A Dremel tool will work great. The ends are staked and if you turn them out without grinding, the threads on the shaft will be f---ed.
     
  19. Spasso

    Spasso F1 World Champ
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    The Weber book I used for the DCOE's on my 240 outlined a basic 'engine off' static set up to use when installing the carbs for the first time after rebuild. This initial setup was good enough to fire the engine and get it to operating tempurature for final sync and mix. It started on the first try.

    I found a good way to test for vacuum leaks around the carb bodies, throttle shafts and base gaskets while the engine is running is to adapt a small tube (1/8" or 3 mm) to a small propane/butane bottle and shoot the gas (unlit) around the carbs and gaskets. If there is a vacuum leak the engine RPM's will change from the intake of the propane.

    No real risk of explosion because of the very small amout of gas being used. Also much less mess than spraying a flammable liquid like WD40 around the engine.(In a pinch WD40 works too).

    DJ
     
  20. bill308

    bill308 Formula 3
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    OK guys, here's some some information I've learned on this subject that is probably not generally known.

    I believe the widely available replacement carbs are 40DCNF-12's as originally fitted to the Fiat Dino Coupe Spyder. A full set can be had new for about $1000. This carb uses a 4-bolt cover and has cast-in air horns or velocity stacks. I don't know how this animal fits the stock 308 air cleaner assembly which uses the bolt through air horns. Anybody try this? The other thing unique to this carb is the progression hole pattern. All the 308 carb cars use a progression hole pattern of 5-holes while the Fiat carb uses a group of 3-holes. There were several variations of progression hole patterns in the 308 series. Also, if fitting these (-12) carbs new, you will have to reuse and retrofit most of your existing lever arms. If one is willing to accept and deal with the differences outlined, this could be a good way to go. New carbs mean none of the needle valves have been overtightened, seats are in good shape, there is no internal corrosion, the throttle valves have not been bent, there is no erosion to the carb throat adjacent the throttle valve, they are clean, and all the lead plugs are leak free. Installation should be reasonably straight forward, check and set the float levels, accept or swap over the baseline jetting, including air correctors and emulsion tubes, bolt on, fire up, sync, and set mixture.

    A new replacement set of Ferrari carbs, with consistent (/nn) numbers is now very rare. After months of trying, I was unable to find or make up a complete set for myself. I did manage to find a NOS partial set of 3 from Dennis McCann last spring, 40DCNF/45/46/ and /48. The /47 to complete the set was not available new from anyone. I managed to source a second /45 from Ferrari UK, which I converted to a /47 by retrofitting a used linkage arm to finally complete a consistent set. Other likely complete sets (/35/36/37/38), (/57/58/59/60), and (/72/73/74/75) were also not available. The thing to remember is that although all the jets, air correctors, emulsion tubes, pump jets, etc., are interchangeable, the progression holes are in general different and the float settings vary between 48 and 50 mm.

    According to the OM's I've looked at, Ferrari carb progression holes go like this:

    (/35/36/37/38) (74 USA GT4) and (/45/46/47/48) (75+ USA GT4) have hole diameters of 0.80, 1.40, 1.30, 1.60, 0.80 mm.

    (/57/58/59/60) (75+ Euro GT4 and /B) and (/64/65/66/67) (Australia GT4) have hole diameters of 1.40, 1.10, 1.60, 1.40, 1.40 mm.

    (/72/73/74/75) (78+ USA GTB/S) have hole diameters of 1.50, 1.15, 1.50, 1.60, 1.80 mm.

    I just installed the new carbs (/45/46/47/48) in my 78 GTS and with the mixture screws set to 3-turns open, the car started up on the second try. When new, the barrels within a carb appear to be balanced by the factory prior to shipment. One balance screw in each carb was always fully seated and therefore the low flow barrel is adjusted up to match the high flow barrel, and a pretty good match it appears to be. A quick balance between carbs and I took the car for a half hour ride. Without further tuning, the low speed behavior is improved over the mismatch of old carbs (/45/73/74/75) even after a thorough rebuild and extensive tuning of these carbs by me.

    Old carbs with an unknown history are a crap shoot. A Weber specialist with the proper tools (anybody have any old Weber tools like a seat reformer or passage reamer, etc.?) can probably save most of these old abused carbs but it may take more than just a cleaning, replacement of gaskets, accellerator pumps, and needles.
     
  21. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    Excellent information, Bill!

    I can confirm that when my source was looking up the cost of replacement parts, he was muttering "40 DCNF" and then "12," so I assume the $450/carb price was probably for the FIAT / 12 one that is (apparently) widely available.

    If a full set of the right Ferrari carbs are hard to find, then I think it makes sense to keep and rebuild these.

    I'm curious, what makes for "abused" carburettors? I doubt that mine have ever been "torn down" to the extent that they would if I get them rebuilt. I myself have had the needles and gaskets replaced with a common "basic rebuild" kit, but other than that, I don't think the carbs have ever been worked on. Does this make for a bad carb? I would think better left alone then messed with by somebody who didn't know what they were doing...
     
  22. bill308

    bill308 Formula 3
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    Mike,

    The kind of abuse I'm thinking of is generally when a component is overtightened or forced in some manner. Mixture adjustment needles are a prime victum. Not only can the tips be deformed and the shaft bent, but this can bugger up the threads in the housing and the seat. One of mixture valves in my old carbs had been closed to the point where the point actually blew through the inner carb wall, into the throat area. Another mixture needle had frozen up in the housing and was bent. Removal of this needle valve left a fatally damaged threads in the housing. Jets can be overtightened distorting the mating seats. Throttle shafts can be twisted. You get the idea.
     
  23. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Russ Turner
    Bill is absolutely correct about the linkage, which is true for all carb applications. Most of the dash applications simply refer to the easily interchangable linkage pieces which are also widely available from numerous sources. As said before, all of the internal pieces for the 40dcnf series are intechangeable.

    The 4 40dcnf-12 carbs on the converted Mondial 3.2 use stock Ferrari air horns (trumpets) and a stock 308 air cleaner. Although not now hooked up, the starting enrichment mechanism is the same (was told not neccesary anyway). Linkage pieces are interchangable, althogh the water crossover in a 3.2 does not support the use of stock 308 linkage, a modified version was used.

    Excellent point about transition holes - have not had a problem using .6 idle jets and .45 accel with good tractability 2000 - 3500 rpm in traffic and acceleration. Of course, the -12s will require re-jetting, but that is extremely cheap and extremely easy. Many 308 owners more optimally re-jet their carbs anyway (numerous old threads on the first board).

    Again, best price I got was $225 per from Bill at GT Auto Parts, but I talked to a lot of folks and many seemed ready to cut a deal for a group buy.

    You just have to decide how important that 4 vs 5 bolt thing is. :)

    hope this helps
    russ
     
  24. Robert Johnson

    Robert Johnson Karting

    Dec 8, 2001
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    Robert Johnson
    No black science here, just get the manual and do it.
     

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