Carb questions??????

[Lee.C]

Right guys - I am going to be using a pair of these Weber 40 DCN's soon and I just want to check a couple of things

1 - 15/16 are the IDLE JETS - correct

2 - 14 which goes at the bottom of the float chamber, are the MAIN JETS - correct

3 - 9 above the emulsion tube are the AIR CORRECTION - correct 

Also there are 2 positions on the accelerator pumps - marked 1/2 - which hole do I use (19)

[Lee.C]

Nobody 

[nicolas]

1. yes
2. yes
3. yes

and that depends on the discharge you need. it normally takes about 3 cc to give the extra boust, but that can vary with the carb. i would set it at the furthest (longest travell) and see what it does. if it needs more dicharge put it in the front one. also looking at the arm on the other side (the one with the spring) can give a clue on how much it needs. no need to fully squeeze the spring as all the movement is gone on the lever then. look at regular type3 carbs (dual setup) and those work a bit in the same way, but with one barrel. i'll look into my book a bit more precisely if i find anything else.

[nicolas]

so i checked it and all is correct i think, but it seems like you have an ealy model carb. as on later models the main jets are located on the stacks like IDF/IDA jetstacks

but i looked up what size jets you could use as a starting point for dual carb setup on a 1641

28 vents / 135 to 140 main / 200 air / f24 emulsion tube (on a DCNF42 there is a f25) / 55 idle (usually on a IDF a 50 works well) / squirters are 50

these are the values from the weber tech manual. my experience is that the idle jets are a bit on the rich side and they are quite generous on fuel to make it all run. hope it helps you out a bit more.

the main fuel jet in the bottom looks indeed as a solex jet from a type3 (and other solexes) and may be interchangeable...

[Lee.C]

Wow thanks dude that really helps - are you sure you want to give me all this info cos I might beat ya 

I only have 24 and 32 venturi's - could I get the 24's machined out  or does anyone know where I can buy other venturi's 

[j-f]

I buy all my jets and vents from a guy in France. According to him, 28 vents are just as good for a stock cam and heads 1600.

There is an online jets and vent calculator on a French aircooled site. http://www.flat4ever.com/?page=carbus

This is what I found for your engine. I suppose max rpm is 5500t? All are minimal value. But as your buggy is lighter than a sedan, the result may vary.

Vents: 30
main: 130
Air: 160
No value for emulsion or idle but I think Nicolas is right.

I don't know if machine the vents is the right way? It will give a straight form and not a curve as original.

On my 1835, I run 32 vents idle 55, main 130, air 175.
 

[Lee.C]

Hey Jf "I don't know if machine the vents is the right way? It will give a straight form and not a curve as original. "

That is what I was thinking - I might have to get you to get me some vents and jets 

As for RPM it revs to approx 5400rpm at the moment with the SINGLE carb so I am hoping to see at least 6500 

[j-f]

Hey Jf "I don't know if machine the vents is the right way? It will give a straight form and not a curve as original. "

That is what I was thinking - I might have to get you to get me some vents and jets 

As for RPM it revs to approx 5400rpm at the moment with the SINGLE carb so I am hoping to see at least 6500 

With my W120 in my 1835 I think 6000 is a max. Engine can rev more but it's useless.

The best way is to make some test and ask somebody that's have experience in carburettor.

And if I can help you, I will do my best. 

[nicolas]

those values might work as well. but i am not sure how a IDF translates to a DCNF. it may be the same. could you take a pic off the jets and venturis? maybe they are the same as IDF and i could hook you up with some 28 vents. 32 are available through CSP, maybe others as well. but i would go for 28 to have the torque off the lower RPM with the w100 cam. and by saying that i think the 6500 range will be a bit too much. i know a W110 goes past 5500 (around 6000), but after that it is all out off flow. but the accelleration is better and faster. and i hope your crank and all is balanced, because above 6000 it really matters. it is always good to have it all balanced, but above 4000 rpm i would do it.

as for helping you, i just want to give you the impression you stand a chance

 

[Lee.C]

those values might work as well. but i am not sure how a IDF translates to a DCNF. it may be the same. could you take a pic off the jets and venturis? maybe they are the same as IDF and i could hook you up with some 28 vents. 32 are available through CSP, maybe others as well. but i would go for 28 to have the torque off the lower RPM with the w100 cam. and by saying that i think the 6500 range will be a bit too much. i know a W110 goes past 5500 (around 6000), but after that it is all out off flow. but the accelleration is better and faster. and i hope your crank and all is balanced, because above 6000 it really matters. it is always good to have it all balanced, but above 4000 rpm i would do it.

as for helping you, i just want to give you the impression you stand a chance

 

Hey dude - I was just guessing at 6500 - we'll have to wait and see 

I will get some pic's of the vents and jets (but I'm pretty ill so bare with me  ) also don't worry about the crank etc its all fully balanced/counterweighed and 8 dowelled 

oh yeah my carbs are DCN's NOT DCNf's 

[Lee.C]

as for beating me 

[Lee.C]

Here you go nicolas - the venturi's are 29mm tall and 42mm in diameter at the top and 40mm at the bottom (there is a 4mm wide lip at the top ) - top left are the main jets BUT none of mine have any numbers and Bottom left are the air correction I have these in 160/200 and lastly on the right are the idle jets I only have 55's 

[beetletom]

lee, thanks for putting this thread up
ive got a pair of 40 dcnf's on dds manifolds
but im still not sure whether to bother with them, as many places don't know a lot about them...?
as they need to be cleaned/rebuilt, i also need a linkage... 

do you know of any places???

[Lee.C]

lee, thanks for putting this thread up
ive got a pair of 40 dcnf's on dds manifolds
but im still not sure whether to bother with them, as many places don't know a lot about them...?
as they need to be cleaned/rebuilt, i also need a linkage... 

do you know of any places???

  there is laods of info about dcnf's (try bergs site) as for linkages just try the normal places samba etc

By the way Mine are DCN's (early 3 bolt type) NOT dcnf's (with 4 bolts) you can see the differences below: ps they are not my carbs/intakes

[beetletom]

ok thanks 

just want to know if anyone can rebuild them really...

[Diederick/DVK]

jeez you've got all the good parts tom. and you're not using any of them. come on

[Lee.C]

ok thanks 

just want to know if anyone can rebuild them really...

DO IT YOURSELF 

trust me its EASY it will only take you a couple of hours - I taught a friend of mine to do his in under an hour and hes been striping and rebulding his 

[beetletom]

will find a gasket set, and i'll give it a go
that pic up top scares me a bit  but they wont need stripping that much..?

[Lee.C]

were getting a bit off subject here  I would never recomend removing the Sharfts/butterflys unless there is a problem ie play or bent, everything else is easy 

[nicolas]

idles are indeed the same as IDF's and vents may be the same as IDF's but top diameter is 40 as well. maybe they can be made to fit, but 29mm could do the trick, 30's may work as well.

 

[Lee.C]

idles are indeed the same as IDF's and vents may be the same as IDF's but top diameter is 40 as well. maybe they can be made to fit, but 29mm could do the trick, 30's may work as well.

 

Hey thanks for the info dude - I got a bit distracted with all Tom's question  I have found this place in the UK http://www.fastroadcars.co.uk/shop/index.php?act=viewCat&catId=5

they should be able to sort out all the Jets BUT the Vents are going to be alittle more trouble