Interesting Weber jetting

[Eljaro]

Hello Chuck,

I made the F14 emulsion tube myself, because I could not find any.
I used a F7 tube, drilled the inside diameter to 3.5mm (it is 3.0 now) and made myself a sleeve with an interior diameter of 7.5mm and an exterior diameter of 8.2mm, length 12 to 15mm.
I used brass. You have to drill on a lathe first to 7mm, then to 7.5 to make the hole as exact as possible.
Then you turn the exterior diameter to 8.2.
Do not remove the burr for now from the edges as this will help to slip the sleeve tightly over the F7 tube.
Click image for larger version Name: F14.jpg Views: 40 Size: 18.5 KB ID: 12161
I include a picture of how this looks like. http://www.clubcobra.com/forums/atta...1&d=1166659604
You have to drill four more holes in the top row (it has only four now) to make a total of 8.
These are the tubes I have in my car right now and they work very well.
Good luck, and let me know how they work out for you.

I am glad to hear that you noticed the improvement with the 40mm chokes. No try to get the transition sorted out and you will experience the real weber feeling.
42 mm chokes may work well too. Just a matter of trying it out.
Stefan

[ENTDOC]

Stefan, do you think a F16 tube is similiar enough to a F14 to yield good results? They are readily available. If not, what other tube would you suggest? thanks; chuck

[Eljaro]

ENTDOC
The F16 tube is common usage and will not lean your low end. You will still have too rich a transition.
The higher the holes on the emulsion tube the leaner the low end gets, which is what you want to achieve. The F7 tube commonly used is for a rich transition and the main problem in that area. That is why you have the black sparkplugs and that is the reason for the stumble: too much gasoline.
I simulated the F2,F3,F14 and F15 tubes which are all supposed to be for a leaner low end.I used several different sleeves with variable holes and the best results were achieved with the F14 tubes. This of course in combination with smaller air correctors i.e. 120.

I would like to see someone trying this out (in combination with larger chokes on a BB)and posting his results. This could come confirm my findings and make weber tuning less misterious for everybody.

[ENTDOC]

so theoretically the F16 should be better than my F7,right? I do not think I am going to be able to come up with any F14 tubes and have no way to make them.

[Eljaro]

yes, the F16 tube will be better than the F7.

[BERNIE]

Originally Posted by Eljaro

Hello Chuck,

I made the F14 emulsion tube myself, because I could not find any.
I used a F7 tube, drilled the inside diameter to 3.5mm (it is 3.0 now) and made myself a sleeve with an interior diameter of 7.5mm and an exterior diameter of 8.2mm, length 12 to 15mm.
I used brass. You have to drill on a lathe first to 7mm, then to 7.5 to make the hole as exact as possible.
Then you turn the exterior diameter to 8.2.
Do not remove the burr for now from the edges as this will help to slip the sleeve tightly over the F7 tube.
Click image for larger version Name: F14.jpg Views: 40 Size: 18.5 KB ID: 12161
I include a picture of how this looks like. http://www.clubcobra.com/forums/atta...1&d=1166659604
You have to drill four more holes in the top row (it has only four now) to make a total of 8.
These are the tubes I have in my car right now and they work very well.
Good luck, and let me know how they work out for you.

I am glad to hear that you noticed the improvement with the 40mm chokes. No try to get the transition sorted out and you will experience the real weber feeling.
42 mm chokes may work well too. Just a matter of trying it out.
Stefan

Eljaro,
Find F14 from pierce manifolds (expensive,but!!!)
Bernie

[Eljaro]

get them !
You can allways drill more holes and make some other tube out of it.
They worked best.
stefan

[ENTDOC]

I did not see F14 for IDA carbs on their site

[BERNIE]

True but they have in stock,received a week ago,
Regards,
Bernie

[ENTDOC]

I found them Bernie, 45 bucks each,ouch

[Rick Parker]

bubbagump:

All this Weber info is sorta "Like A Box of Chocolates" huh? Tastes a little different to everyone. Good eat'n though!

[Eljaro]

Has anyone fitted 40mm venturis to his 48IDA and has some experience to tell ?
Or is everybody still choking along on 37's ?

[ENTDOC]

I now have 40's and the car runs better than ever and the plugs are not sooty anymore. I really think 42's would work great. I still have a little stumble at 2400 or so after changing to F16 e tubes. I probably need to try different idle holders(ie-less than 120's.)

[traindriver]

Reading Eljaro's tuning work has given me some motivation. I purchased a PLX R300 logger. I'm logging AFR, RPM and TPS. I made a base line log on my 3 mile test run and found one particularly interesting item. It always bothered me that if you set the idle mixture to 'best lean idle' like you would with a 4bbl, you get horrific popping through the exhaust during letoff and slight throttle openings. By opening the mixture screws about 1/2 turn as Eljaro did, it goes away. My logging session shows why. With the idle AFR set correctly for BLI at 13.5 it would lean to 18-20 just off idle (major poppping) (TPS <=4%). As the throttle opened more (TPS>5%) the AFR dropped back to 13-14. To figure out why...I removed an idle mixture screw and the transition hole plug. Shining a flashlight in the airhorn revealed both transition holes above the throttle plate...not good. Then I closed the idle speed screw unitl the lower hole was covered. This is the correct idle position according to the Weber tuning manual, the TPS now read 5%. Of course with this setting the engine would idle at 2000 rpm. So to combat this, you have to open the mixture screw to make it rich at idle, then as the throttle begins to open but has not yet uncovered the lowest progression hole to engine vacuum the mixture will lean out to 13-15 as the throttle opens.

All for now, back to tuning.

Chuck

[Eljaro]

I found two merchants selling F14 tubes. I just ordered 2 sets of 4.
Check these two links:
http://cgi.ebay.de/Weber-DCOE-DCO-SP...QQcmdZViewItem
http://www.dansperformanceparts.com/...ggyintake3.htm

Remember that after much testing on the road and under load a modified emulsion tube similar to F14 worked best on my 427 C/O.
The F14 tube has one advantage too, it has lotsa meat and is easy to modify, like drilling the interior deeper, turning the outside thinnner and drilling as many holes in it as you wish.

Good luck.

[Cal Metal]

Eljaro:

I might have missed this in a previous response, but what was your experience if you employed the F14 without any additional drilling. What type of response did you have, particularly in the transition stage?

Thanks

CM

[JCoop]

Glad I stumbled upon this informative thread.
I thought I had gotten my weber tune (48IDAs on a crate 302) to 95% on my CAV.
Idles well, with just an occasional stumble at 2800, but my exhaust and plugs are still black; even after changing the idle jets from 65 to 60. I guess I have the stock 37mm venturis and after reading this, I think I'd like to try the 40s and go down even more on the idle jets to 55.
So where can I order them?

edit: never mind, I saw the link to dansperformanceparts.com. Ouch! Almost $200 for 8!

[ENTDOC]

Ray, keep in mind we are using 40's on stroked 427's, not that they might not work for you on the 302. What emulsion tubes are you running? chuck

[Eljaro]

CalMetal

I used F7 tubes and modified them with a very thin sleeve (0.5mm wall thickness) with 4 holes to partially or totally cover up the bottom holes to see what happened. So I kept doing mods to the sleeve and the emulsion tube until what I had as a result looked exactly like the F14 tube..
But my F7 tube is not a perfect F14 , because the 8 middle holes drilled at an angle are not 100% covered. There is a gap between the sleeve and the smaller diamater part of the tube where these holes end inside the well.
I also had to drill the 4 aditional holes at the top, where the F7 tube has only 4 but the F14 has 8 holes.
With this arrangement I was able to get rid of the bog and the lean condition, according to the OS2 sensor and the gage. Then I went about to reduce the main jet to the point where on full load at 6000 rpm the AFR would stay stable and not go up..
After that the car ran fantastic, I would say perfect. Plugs are tan now, whereas before they were black as a coal mine and no main jet would correct that because smaller jets would lean out at WOT and that is a no-no.
I have ordered a set of F14 tubes and once I have them I will try them out. If I am too rich at the transition I can drill some holes where the F7 has the angled ones and correct for that.

[Hans-Olof Blom]

Vee Dub Parts Unlimited sells 40mm chokes for $37.50 a pair.
They also have 42, 44, 45, and 46mm chokes.

http://www.vwparts.net/JC40V.html