Eljaro,

Love your thread, I have learnt a lot. :)

Just one question with your pump bleed, even a zero bleed should vent back to the bowl since the inlet ball is not seated at rest, it seats when the pump is activated, I'm thinking the pump outlet check valves need to be heavier?

Your thoughts?

I recall reading that on the FE with an angle milled manifold the the nozzels had a tendency to drip because that with the carbs at an angle the check balls were not fully on their seat??? Not sure if that is fact but I'm just repeating what I read in another thread or website.

Yes this could be the case with carbs that are mounted beyond the maximum angle as designed by Weber.

I haven't seen a spec for deviation from the vertical plane for IDFs or IDAs, but the maximum recommended above the horizontal plane for DCOEs (sidedraughts) is 7 degrees as specified by Weber.

I have DCOEs going on one of my other cars, I haven't measured the angle yet, but I know it will be close (touch and go).

I think that how the float can control the average float level has a bearing on this.
With the downdrafts, if they are tilted towards the pump jet side of the carb, does this bring on this issue?

Where do you have get your 0.85 air correctors difficult to find in these size (0.80/095)
Thanks

I do not know what how the check valve in the bleed jet exactly works, but you can blow through it one way only if it is a 0.00 one. On rest it apparently is closed and the gasoline in the pump circuit boils over, creates pressure and escapes through the pump jet into the throats.
With the 0.50 bleed this did not happen, so it looks like the pressure in the pump circuit escapes through the bleed hole and you do not get the nasty spill. Unfortunately the .50 spill is too much and creates a slight bog, so I am waiting for a set of 0.35 to arrive
At times I thought this had all to do with the float height and heat to the carbs through the gasket, but I have learned that it has nothing to do with that. I have the brass float at 4.2mm from the lower carb body surface, and it is ok so, since it compensates for the inclination of the carbs. I double checked on that and it is the best adjustment so far.
I am even thinking of removing the 10mm heat isolators from the carbs, which give me headaches because they raise the carbs and the air horns are touching the hood and pushing the two front right horns off its seat in the carb all the time.

I could not find .85 air corrector jets, so I took 2.20 air correctors . filled the holes with tin solder and drilled on the lathe a 0.75mm hole, which is the drill bit I could find around here. Works perfectly and gets away with top end leanness. Tried them out today with great success.

Yes, unlike an old Holley with it's steel inlet valve, the Webers inlet valve is very light and when submersed in fuel would be floating shut.
I always thought they were a "hanging ball" (non seated) like an early Holley.
It's a shame Weber doesn't make one smaller than .35, they must have thought there's not much difference between a .35 and 0.00.

A .35 is near enough to a number 80 drill bit, but you can get metric drills.
I have a set down to .3mm, so you could make you own .30mm bleeds.

0.35 mm bleed is half the surface as the 0.50. It will probably be better than the 0.00, because when I had the 0.00 on I did get a black cloud coming out the exhaust on acceleration. The bog with the 0.5 is minimal now, so 0.35 will probably be best. I will find out when I get the jets.
Drilling 0.35 mm on a curved surface is going to be a nightmare. Those drills break just by looking at them and they are not cheap. Maybe still best and cheaper to get a set of bleed jets. I got them from http://www.dellorto.com/

You're on the money, and I guess that's how Weber decided on the final small sizes.
Sounds like 35s will fix your issue, I'd be itching to get the lids off. ;)

my cam has the following specs:

duration- intake 242, exhaust 248
LS- 110 degrees
lift- .645 intake and .635 exhaust..

I have run the webers successfully with the 40mm chokes, and am now in the process of tuning the 42mm ones. Takes a totally different emulsion tube (the F14 is no good any more!). If the weather this next weekend allows I will be fine tuning and will post the results.

Eljaro, looking forward to the results of your new modifications.
After reading all the info here in this thread, I decided to increase the chokes from 37 to 40 before I even install the conversion on my 393 w stroker. When I recieved my new 40's they looked as rough as the 37's did, so I decided to machine them internally. Made up a profile tool bit the same as the contour of the 40 and machined away. Well the 40's had to be machine to 41.5 mm before they would all clean up round and true. These castings are very poorly made and not consistant. Some of them would have cleaned up to about 40.75 mm and the others had to go as far as 41.5 to clean up. This will give you an idea of how much different one of your carb bores could be different from the other, right from factory. So now my delema is ....do I use the 41.5's or do I machine out the set of 37 mm chokes to 40 mm like I was going to try? Would you think the 41.5's might be too big?.....Anyone have comments?

Percentage wise, that is a pretty small jump from 40mm to 41.5mm. I would be inclined to try it with the 41.5. Were these chokes just recently purchased? I have used a polishing compound mounted on a drill bit that cleaned them up to the point that they were as smooth as glass. These must have been pretty rough.

CM

I have polished every Weber venturi I have purchased over the last 25 years.
DCD, DCOE and IDF, they all polish up like a mirror with minimal metal removal.

41.5 is a about 7.5% larger than 40 in cross sectional area.

You can only try your 41.5s and see what happens. :D

These were recently purchased (the 40's) as well as the complete conversion set up with the 37's in it. Both the 37 and the 40 are very much out of round with different bumps and hollows on the internal surfaces. This is to say when measuring with a inside micrometer. Yes I would agree that if you polished them up they would appear to be quite nice as I did polish one up before turning them. The thing is when you put them in a lath and dial them up you would see how far out of wack they really are to each other. I was very suprized to see the variation from one to the other in size. I can see how they could have produced very different results from one cylinder to the other if I would have used them the way they where. I am a bit of a fanatic when it comes to making everything identical from one cylinder to the other. This is why I choose to machine the bore so that they are all exactly the same. I guess I will try to use the 41.5's and hope they are not too big.

I did machine my 37mm chokes to 39mm, and ended up having to go to 40mm because of the final finishing. Make them all 41,5mm, or take your 37mm and make them 40mm.
I have been working on my new KC 487 sideoiler, where all the settings I had did not work any more. I tried the new F14 tubes I got and they were too lean in the low range. I did turn the outer diameter from 8.2mm to 7.9 and it was much better, but still probably needed some more holes below the top row to work well.
Before going to drilling the F14 tube I did take the F11 tubes, soldered the lowest row of holes shut so as to make an F15 tube out of it and it seems to be the best so far. I have 140 main jets on it right now but will go to 135. The air corrector is at 120 now. Idle is 65 with 120 holder. Pump bypass jet is 0.35.
I have had issues with the pump jets. On idle I have seen some of them dripping gasoline and on shutdown when the webers absorb the heat from the engine and get warmer fuel drips from the pump jets into the throats. No good!.
So I removed all the pump jets, took a 2mm tap and screwed it inside the brass plug in order to pull it out.
Some of the seats for the small ball inside looked terrible, so that closing the hole with the ball must have been impossible.
I drilled a conical shape with a 3mm drill on the brass plug and and replaced the 2.38mm steel balls with 3mm ones. They are slightly larger and twice as heavy and I must test how they work. I believe that if the vacuum is very high such as with our Hi-Po engines the vacuum is drawing gasoline out of the pump jet because of defective manufacturing process and throwing any idle-transition tune up out of kilter.
If the weekend is sunny I will try it out and post results.

Attachment 14633
This is how one of the the pump jet seat for the ball inside looks like. It has a spiraling cut which makes it impossible for the ball to seat right and close the pump circuit. The vacuum in the carbs was thus pulling gasoline through the pump jet. Some ball seats looked better, but I drilled on all of them a conical seat for the 3mm ball to fit right.
The result has been that the webers do not dump gasoline any more into the throats when resting and absorbing the heat from the engine.
So that one problem seems to be taken care off.

This is just another flaw in the manufacturing process of the carbs that makes you really wonder who the heck is making these parts. Especially when you think of the money we pay for them. The more I look into these carbs the more I am finding that needs to be fixed or replaced before I even install them. After Eljaro's discovery in the pump jet seats, thats one more thing I have to check and may have to fix. Good to know about ahead of time.....thanks for sharing all your invaluable discovery's Eljaro!

Thought you night be interested in these. They are directly from Webers book.
http://www.clubcobra.com/forums/atta...1&d=1236117335
http://www.clubcobra.com/forums/atta...1&d=1236117344
http://www.clubcobra.com/forums/atta...1&d=1236117353

Ejaro,

Did this correct your problem with the dumping of the fuel?

"Made in Italy" :(

Repairing the pump jets seat did help in preventing them from dripping while the engine runs. The vacuum inside the Webers was drawing fuel out of some of them. That does not happen now.