Jet sizes for Weber 34 ICT's?

[sparkywig]

Hello there, I hope somebody can help?

I've got a stock 1600 single engine in my bus with a new pair of Weber 34 ICT's fitted.
I've set them up according to the redline weber guide, but it wouldn't start without the idle speed screws being wound out about 3 1/2 turns. I've also had to screw the mixture screws right in to get the engine to run on idle, but can't get them to run on throttle. Lots of popping and banging going on.
The obvious thing is that it's running too rich, so can anyone give me some guidance on jet sizes?

At the moment the carbs are as supplied;
main jet 130
air corrector 160
idle jet 52


I've spent the whole weekend trying to get my bus to run so many thanks in advance.

[TexasAirCooler]

From what I understand about dual carbs they will need to be synchronized to stop that.

http://www.aircooled.net/gnrlsite/resource/articles/dualcarb.htm
_________________
Terry

Common Sense Is A Flower That Doesn't Grow In Everyone's Garden.

[babysnakes]

I never had to synchronize my 34ICTs. I always thought that was just for 2bbl dual carbs. I have a set sitting in the garage that worked fine a LONG time ago. I'll dig one up tonight and check the jets and screws.

[mnskmobi]

[sparkywig]

Thanks for all your replies.

I forgot to mention that I'm running an 009 as well.
Yes, I've cleaned the carbs through with carb cleaner, and a balance pipe is fitted between the inlet manifolds.
They are synchronized as well.
Just can't get it to run on throttle without the popping and banging.

[Desertbusman]

009 is common when running baby Webers. Works great. Just make sure it is timed correctly. Where did you get the carbs? Give them a call. They should provide jets for your specific engine and aslo help you thru the problems. Still doesn't sound like they are synced. It's also a real chore to get the manifolds in the tins and to the heads with a leak free install. When you cleaned them did you also blow thru all the passages? Of my 2 new ones, 1 had junk in it. Also compare the jets between the 2 carbs. Sometimes they get reamed larger. Really pay super attention to the coordination of the linkage to both carbs.
_________________
71 Superbug
71 Westy

[TexasAirCooler]

Check this out, there maybe something your missing yet.

http://www.aircooled.net/gnrlsite/resource/articles/dualcarb.htm
_________________
Terry

Common Sense Is A Flower That Doesn't Grow In Everyone's Garden.

[sparkywig]

Thanks.
I haven't got much work on at the moment, so after the wife goes to work in the morning I'll have a day trying to sort this out.

[alien8]

52 idles are pretty lean for a stock 1600. 3 1/2 turns on the idle screw indicates this. The mixture screw is not an indication of running condition if the idle screw is more than 1 1/2 turns out.
I say its running lean not rich.
Try 57.5 or 60 idle jets.

[kingodirtp3]

i'm running 60 idle and 140 main jets. recommended by lowbugget and
aircooled.net. i have a 1600sp with header, 1.25 rockers, massaged
heads w/ valve job, SVDA distributor. runs great, plugs have a nice
brownish color to them.

[sparkywig]

Apprently it's a fuel pressure problem.
The carbs can only handle about 3 - 3.5psi while the stock pump puts out between 5 - 8psi.
So I need to fit a regulator and then play with the jet sizing to get it to run properly.

Thanks for your replies

[kingodirtp3]

i have the stock (alternator) pump, i havent checked the pressure but i dont have any problems.

[atquexata]

I have a dual icts too in a 1600 dp with 041.My idle jet are 52.but i only need open the mix screw 1 1/2 turns for run well.Why?

[alien8]

[atquexata]

1 3/4.with 1 1/2 the engine run ,but with low rpm.In my country the fuel is 98 octanes.

[alien8]

More than 1 1/2 out on the idle screw is lean idle jets
Mixture screw assumptions are based on the fact that the idle screw is no more that 1 1/2 turns out maxium, as from Weber set up sheet.
52 idles are a touch small.
It may run fine as it is but there is every chance it could run a whole lot better.

[atquexata]

What action do you recommend for my engine?

1600dp 041heads.4 to 1 exhaust.1.25rockers.

[alien8]

This is just information regurgitating but I thought it might be usefull to you and the original poster. This is from Weber tech. sheets.

The secret to understanding the critical nature of the carburetor set up and the advantages of a WEBER over other carburetors is the Idle circuit. Referred to as the low speed circuit by Weber, this circuit is responsible for 80% of the driving operation. This is the reason that the Weber should give a fuel economy improvement over most factory Carburetors along with significant performance gains. In the worst case you should not see a significant fuel economy loss over stock, while improving HP & Drivability.
If the mixture screw is more than 21/2 turns out turns then the Idle jet is too lean (too Small). When the mixture screw is less than 11/2 then the Idle jet is too rich (too large). These assumptions are based on the fact that the speed screw setting is not opened more than 11/2 turns.
.
If the speed screw has to be opened 2 or more turns then this is also an indication of a lean condition usually requiring greater change. At times it may appear to be showing signs of richness or flooding it is really a lean condition.

please understand the need to keep throttle plate as near to closed as possible so as not to prematurely expose the transition holes. This is what causes the visible rich condition, and confirms the need to increase the jet size.

[alien8]

[sparkywig]

I've been told by a carburettor man over here, that the problem I have is with the fuel pressure pushing too much fuel through the large needle valve (bearing in mind that type 3's and 4's have 120 needle valves) and and that the emulsion tubes allow too much fuel through just off idle.

The 34 ICT was developed for single use on a Bedford CF van over here in the UK, and all the carbs supplied are jetted for this, not for a VW.
The jets as supplied are;
idle jet 52
main jet 130
air corrector jet 160
emulsion tube F78
needle valve 175

The recommended jets for a stock 1600 single/twin port are
idle jet 55
main jet 150
air corrector jet 170
emulsion tubes F3/F6
needle valve 125-140

F3/F6 emulsion tubes have no drilling high up on the tube allowing the idle jet to do its job without adding early fuel from the main jet.

I have also been told that if I solder up the top holes in the F78 emulsion tubes that will stop the off idle fuelling and then the 55 idle jets will be correct.



Clear as mud?

Still have to fit a fuel pressure regulator though....