Need help with a 40 DCNF laying around, and numbered drill bits

[Multi69s]

Having a hell of a time trying to jet carbs for a new engine build (they won't). The engine is a very mild 2L Type 4 with dual 40 DCNFs. Its not an engine (I'll describe the engine in another post) issue, since I tried other carbs, and they didn't react the same way. I've jetted a lot of engines, 4 stroke, 2 stroke, many different types of carbs, and even 2 stroke methanol, "no problem", but I have been chasing my tail on these carbs. I have also been working with Pierce Manifolds, and they are stumped.

The issue is that the engine is running pig rich (11 A/F) with soot on the plugs, and exhaust, and no matter what I do it doesn't change. I think I found the answer, but I need the help of someone that has a DCNF carb, and either a set of numbered drills bits, or marked jet drills. I could write a page of the things that I have tried but, what I believe the problem is, is that the Idle Air Jets are too small. The Weber book calls them Calibrated Bushes.

When you remove the top of the carbs, you will see little brass donuts on top of where the idle jets are. If someone would be willing to measure theirs with either numbered drill bits or millimeter jet drills I would be very grateful.

I have already compared two different sets carbs and this is what I found.

On my carbs I inserted the smooth end of a #56 drill bit and it was a snug fit, so my Idle Airs are 0.045" in diameter. However, on the other carb a #51 drill bit was loose, and it measured 0.068 in diameter, a #50 wouldn't go. The penny is just for size reference.

The carbs with the larger Idle Airs are actually off of a Ferrari 308. So before I start drilling, I would like to compare my findings with that of a carburetor, that was actually ran successfully on a VW engine. If someone could check their carbs, I would really appreciate it.
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
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[modok]

comparing the idle air jet sizes is.....sorry to say mostly meaningless without measuring the progression ports also.
Generally the more and/or larger the progression ports are, the larger the air bleed is also, it matches.

ONE way to fly is, you can tune the rest of the carb to match what these sizes are, follow the tuning and it will lead you there, but it may not be the venturi size you want.

Or you can change the progression ports and idle air bleed to match what size vents and ect... you WANT to have, basically make the carb body match the vent size and jets YOU want.

If your trying to use jetting info that doesen't apply to the model of carbs you have perhaps could be all confused and better off to have known nothing and just followed basic principles.

Probably part of what was special about the "berg specials"
But heck those secrets are... so long gone man, they might just tell you what they were... if asked. i would.

[Multi69s]

Believe me, I started with the basics.

Started with best idle method that is commonly used, cruise A/F -11s, wide open fine.

I first tried the carbs jetted as they came, cruise A/F -11s, wide open fine.

Went to the most common DCNF jetting, cruise A/F -11s, wide open fine.

Went by Weber book matching vents to jets, cruise A/F -11s, wide open fine.

Tried suggestions from non Weber books, cruise A/F -11s, wide open fine.

Made damn sure that in any tuning stage that I was not uncovering a transition port during idle.

Set A/F to 17 at idle, cruise A/F -11s, wide open fine.

Plugged enrichment circuit to make sure that no fuel was leaking through: cruise A/F -11s, wide open fine.

Now obviously the wide open A/F would change as I went through my tuning process, But I could correct it. However, what is not changing is A/F at cruise.

As I stated, I was not working alone on this, but with experts that their only job is carburation, and the list I just gave is far from complete.

It is far more helpful to think about a viable solution then to shoot someone's possible solution down
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
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AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[modok]

So... you didn't try smaller idle jets?

[modok]

Screw the experts. Sorry the books and the experts are so stupid that they can't measure a hole like you and I can.
So as I see it your started on the right track. Measure ALL the holes.
And a quick google search i just did is very encouraging, uncovers more info all the time. Berg did indeed re-drill the progression holes from one recent account. Really I sense a change in the attitude for the positive direction, shifting away from fierce competition when this was hot stuff, towards more of a historical reenactment....which is ok, presumably we are reenacting it because it was fun? i think so.

IMO the decision on what hole to change depends on WHERE it was too lean when you tried small idle jets. The hole that is controlling that spot is the hole to be changed. is that simple or what?

[modok]

And why is that....is because it's easier to go bigger than it is to go smaller.

I don't know if I'm making it too simple or too complex or more likely jumping too far ahead, let me know. you want stories of other people making the same mistake I suspect you could be making then we can do that. I'm included too. I did it too. But I'm not alone. mharney, mcdragracer, with the search feature i could find many more, with google i can find more yet, sidedraft guys on sideways technology...... in fact empi even did it. They wanted to copy the 40DRLA that CB sold but they copied the wrong carb. Those haven't been popular.
But if they had measured ALL the holes.......
then the problem would have been clear to see

[Multi69s]

I did try smaller jets, in fact I tried the smallest Idle jet that they make a #40. I also drove the car without the jet stacks, so driving just off of the idle jet, pig rich. We both know that you need the proper ratio of fuel/air for an engine to run right. Originally I was concentrating on leaning out the fuel. However, I can not lean it out any further. That got me to thinking that I am not getting enough air. What controls the air? Air correction jets (high), Idle air jet (low). Since all of my issues are low, that's what got me thinking about the idle airs.

As you noted, there are more then one versions of the 40 DCNFs. Some are very specific to different vehicles, like Ferrari, and Fiat. So, when you get a set, you don't know what you are really getting. That's why I am hoping that someone could check a carb that they knew would run on a VW.

We really don't know what Berg was really meaning when he stated that "the 40 DCNFs transitions ports are too big". It "Might" be that they are too big for the size of the idle air jets.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[modok]

I agree, and enlarging that air bushing might get a darn good idea for fine tuning but still something isn't adding up. A 40 idle jet should be only 64 percent as much fuel as 50, so that result is just strange, like the idle jet is bypassed entirely. Will it run with the jets soldered closed?
You might put some marker on the end of the jet and make sure they are seating. Trace that circuit back to the main well and see how it works maybe a plug can come loose and bypass the idle jet like it does in dellortos?

Kind of have to say that it It could be accelerator pump fluttering, or main nozzles dripping, but it probably isn't.

[Multi69s]

[Clatter]

I only have a set of 44 DCNFs so i’m not sure it would help you to measure them.
PM Brent. He has a couple sets of 40s in a box he’d likely measure for you.
I like Glen’s idea that the pumps are leaking.
Figure out a way to plug off the pumps entirely and see if the richness goes away..

There’s got to be fuel coming from somewhere it’s not supposed to.
Just have to figure out where.

Are the enrichment circuits completely blocked off with plates?
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[Brent]

[Brent]

[Multi69s]

Are the enrichment circuits completely blocked off with plates?

Yes, and the jets have been soldered close

Tell us what size idle, main, ET, air corrector, venturi, and aux venturi you have.

I have made many different changes, but this was my last setup
Idles: 40
Mains:125
ET: F24
Air Correctors: 195
Venturis: 30mm
Aux Venturis: 4.5

It sounds like to the accelerator pump is leaking.

At idle, there is no leaking out of the nozzles, butterflies are bone dry on top. I was toying with trying to rig up a video camera, shooting down the carbs while driving. Don't think that will work.

There are 3 sizes of accelerator pump nozzles IIRC.

Yes, you can choose between 45s, 55s, and 65s (I have all three). However, I am using the NLA 35s right now.

Idle air jet???

Brent, some carbs use an idle jet, that also has an air jet built in. When purchasing, you can select which combination of fuel and air orifice sizes that you want. However, with the DCNF, the air size is permanent, and they are called calibrated bushes #20 in the picture. That is the part that I trying to get a measurement of. I used the shank of numbered drill bits to measure the two different styles of DCNFs that I have. If you could measure yours, I would greatly appreciate it.

_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[Rob Combs]

I'm guessing if you've been talking to Pierce, you've probably already covered this but here goes....Are all 4 plugs sooted up? If so let's make sure to consider things common to both carburetors.

What's your fuel pressure? Are you on a regulator?

Are the float levels correct? I mention this because I set mine both incorrectly by the same amount and spent hours modifying emulsion tubes and trying other "fixes" in service of chasing driveability issues. When I revisited float adjustments I saw the error of my initial setup and adjusted accordingly. I was quite impressed at the difference a small adjustment made and immediately started reversing my "fixes" until I was left with non-modified carburetors that are set up and jetted decently (still not perfect yet but good enough to not tinker with it every weekend). I made a float level checking tool out of a letter opener and it has worked out well.

Hope this helps

[Multi69s]

Rob,

Suggestions are always welcome:

All four plugs are sooting up

I am running a regulated electric fuel pump, pressure is 2.75lbs at idle and drops just a hair when the mains kick in. Verified with two different gauges.

Float level was triple checked, checked for fuel in the floats, and swapped out the needle and seat with a known good set. Also, and I am running it a little less then the recommended height right now.

I made a float level tool out of a caliper, but I am curious at what your "letter opener" tool looks like.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[Rob Combs]

Having some computer issues this morning so not able to get you a pic, but it's as simple as simple gets. The letter opener looks like a miniature medieval sword that I've marked off at 49 mm from the tip and sharpied it red, then added I believe 8.5 mm from there, marked it off, and sharpied it black.

That way I can see the where the float initial position and float droop should be in low-light/low visibility areas like my poorly lit shared garage.

Back to your carbs, is there a way you can check all the low-speed circuit passages with soapy water and some compressed air? The people who chimed in before me are right, the extra fuel's got to be coming from somewhere, possibly through the carb bodies (lead plugs leaking/missing?) but very strange that it's happening somewhat equally on both carb bodies. I'm still thinking points of commonality, perhaps someone before you attempted to rebuild them and missed/broke/drilled/damaged/destroyed something on both units???

Hope this helps somehow...

Rob

[Multi69s]

Rob,
Since it is doing the same thing in both carbs, That make me believe that it is the same problem in both. In the past, I have purchased brand new carb gets, and have actually received bad carbs before,

As far as pressurizing. The only way that I can think of doing it would be to sacrifice a complete main jet stack by soldering up some holes. I would need to be able to pressurize the emulsion well with out air escaping into the float bowl, or out the Aux venturi discharge port. Then solder up the side holes on an idle jet, and solder the idle jet to a blow pipe.

I don't even know if that would work. I think that air would still escape out of the discharge port. It will probably be about a week until I can get back to it though.

I'm in the middle of a timing change fix on my son's Altima. This job is a B*&CH, some engineers were idiots. I've done this job on other cars in the past and they were a cake walk compared to this thing. It wasn't even the chain or tensioners that went bad. Some idiot at Nissan didn't torque a chain guide bolt correctly. It came loose and allowed the guide to be eaten up by the chain. Rant over

Thanks for the suggestion.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[earthquake]

The fixed bushes on a 40mm DCNF 12 I have on hand are approximately .045", I don't have a set of drills to get a better measurement right now.
Hope this helps.

eQ
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[Brent]

I measured (two 42's), both are the same and fit a #56 drill snug.

Edit: Hopefully you didn't drill anything.

I measured two of each.

40's, #50
42's, #56
44's, #54, almost a #53, but not quite

Interesting that 42's are the smallest, which also seem to be the most common Berg 'Special'. I wonder if they drilled that out as part of the special process.

I have 36's on my Fastback, I should measure those just for reference.

I'll dig out my good calipers and measure the bits just to be sure and send an update.

If you do start drilling them, maybe start with a #54, then #52 to #50? See how it changes things.
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[volksworld]

had an issue a couple of years ago with a set of 40's...these were brand new ( itialian webers)) when installed and jetted on a fresh rebuilt engine...a year or 2 later the car came back running rich...the phenolic floats had absorbed something and were no longer normal buoyancy...2 new floats cured it...normally you see stuff like this on 20 year old carbs not new ones