Alfa Romeo Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter #1
I was going to try changing the main jets on my Weber 40dcoe2 carbs (Italian made) and when I bought the new jets, there’s a difference in the design...see picture. The old one has a ball bearing within it and also a “step” on the piece that goes into the emulsion tube. The new one doesn’t have the ball bearing, and doesn’t have the step - so it doesn’t seat into the tube quite all the way...is it okay to just use the new jet ?? Or do I need to get the “new” emulsion tube to go with these main jets ?
Any help, much appreciated.
thank you
Roger
 

Attachments

·
Super Moderator
Joined
·
11,550 Posts
The ones with the ball are REALLY old. Possibly 1960 vintage. We used to just remove the ball from these. Somewhere I've still got a few. The new ones are preferred in all applications.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #3
The ones with the ball are REALLY old. Possibly 1960 vintage. We used to just remove the ball from these. Somewhere I've still got a few. The new ones are preferred in all applications.
thank you Gordon.
When I push the new one into the tube it barely covers the slots on the side of the (new) jet because it doesn’t have the “step” (the diameter inside the emulsion tube gets narrower with depth),.....do I need to get new tubes ? I’m presuming “yes”

out of curiosity: what did the ball bearings do? Somehow regulate the flow ??
 

·
Super Moderator
Joined
·
11,550 Posts
I've several really ancient F-16 e-tubes for a pair of 40DCOE2 with 3 digit serial numbers, likely 1960. They have no step in the main jet end of the tube. What are your E-tubes numbered?
If they are stepped, just cut the split end of the new jets shorter to fit.
The original idea behind the ball check was to maintain a higher level of fuel in the e-tube than in the float bowl, so they would transfer from the idle circuit more easily. That did not work as planned as fuel leaked back down past the ball so the higher fuel level in the e-tube was not happening. Pick-up from the main jets was quicker without the ball, so it was quickly replaced with jets without the ball.
If your E-tubes are numbered correctly for your application, I would not bother to replace them, but just alter the height of the new jets. The jet must be seated flush in the tube for the E-tube to installed to it's correct depth by the e-tube holder. The hex should seat flush with the end of the e-tube. Then the jet taper seats in the Weber body seat. The e-tube sits at the correct depth in relation to fuel level in the bowl, and so on.
Best, Gordon
 

·
Registered
Joined
·
66 Posts
Discussion Starter #5
Okay - that makes sense. I can take about 1mm off the split end of the new jet and they'll fit snugly into the current emulsion tubes.

My Emul tubes are f16s.....maybe "step" is too strong....its more like a "domed" shape (but the current jest are stepped - hence they fit (see pic in original post)...but whatever you want to call it, the new jet won't go all the way in because its obviously wider than the current one at that end (see original pic for comparison). If I take about 1mm off, then all will be well....


much appreciated !
Roger
 

·
Super Moderator
Joined
·
11,550 Posts
Jets are considerably cheaper than e-tubes. Before you trim the new ones, try a bit more pressure pushing them in the tubes. If the tubes are not stepped, they should fit. I've never seen stepped e-tubes, but that does not begin to suggest there are none.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #7
Jets are considerably cheaper than e-tubes. Before you trim the new ones, try a bit more pressure pushing them in the tubes. If the tubes are not stepped, they should fit. I've never seen stepped e-tubes, but that does not begin to suggest there are none.
I’ll take another look but the tube does diminish in diameter with depth (a domed shape when you look in)...the new jets push in (fairly easily) but then come to a “hard stop”...but I’ll try and measure it and see if it’s possible. But, as I said, if you look at the originals, they have that step end which allows them to go all the way in....
Thanks again!
 

·
Super Moderator
Joined
·
11,550 Posts
Ok, it's probably NOT a step. I looked at the oldest F16 e-tube I had, in my 1960 40DCOE2's. I checked all four. NO step. They all looked like this.
1624508
I then measured the depth of the bore to the visible ledge, both on the 60 year old Italian original Weber components and on the brand new Spanish F16 pictured above. The new one measured...
1624509

almost 6mm deep. The 4 old ones were 5.99 to 6.01 mm deep, .06 to .08mm deeper.
I then began measuring the height of the split skirts on about a dozen random jets, some quite old, and others brand new. The shortest were 5.48mm tall, the tallest 5.82 mm tall. I then installed the tallest one I had, a new one in the 5.94 new, Spanish F16 e-tube.
1624510
If you send me your 4 jets, and 4 tubes, I will probably be able to assemble them for you.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #9
Ok, it's probably NOT a step. I looked at the oldest F16 e-tube I had, in my 1960 40DCOE2's. I checked all four. NO step. They all looked like this.
View attachment 1624508 I then measured the depth of the bore to the visible ledge, both on the 60 year old Italian original Weber components and on the brand new Spanish F16 pictured above. The new one measured...
View attachment 1624509
almost 6mm deep. The 4 old ones were 5.99 to 6.01 mm deep, .06 to .08mm deeper.
I then began measuring the height of the split skirts on about a dozen random jets, some quite old, and others brand new. The shortest were 5.48mm tall, the tallest 5.82 mm tall. I then installed the tallest one I had, a new one in the 5.94 new, Spanish F16 e-tube.
View attachment 1624510 If you send me your 4 jets, and 4 tubes, I will probably be able to assemble them for you.
thats a very kind offer!
I’d love to try and put them together myself - obviously I don’t want to damage them.
I’ll measure the depth first and see if they measure the same as yours....
 

·
Registered
Joined
·
66 Posts
Discussion Starter #10
Hi Gordon -
Just to put this to rest, I’ve attached pictures of the old and new main jet in the same emulsion tube. You can see the discrepancy in fit. Per your original response the new jet doesn’t sit deep enough....
I’ve also attached a better picture showing the “dome” (with arrow).
I found 4 new f16 emulsion tubes at a reasonable price so I’m going to try those rather than mess with the pieces I have. They’ve survived 50 years....they deserve to be left alone.
thanks for all your help!
Roger
 

Attachments

·
Super Moderator
Joined
·
11,550 Posts
These are, as I suspected, very early 40DCOE2's made in the first year or 2 of production. They are quite valuable to a car restoration. Yes they are a matched pair. Generally, early matched pairs will be 50 to 150 apart, and later the spread widens somewhat. The earliest DCOE2 I've restored was # 51. My own early set are 461 / 514. Note that the progression hole covers on those numbered under 'about' 1000 are 7mm then changed to 8mm. Should you ever have yours rebuilt, it should be done professionally, as these early ones are uncommonly seen and non-replaceable. Yours will also probably have 23gram brass floats, which are almost too light with todays fuel replacing gasoline. Later 1300 Veloces and ALL other 40DCOE2's went to 26 gram brass floats, which are ok with "fuel".
There are other differences on the early 2's. #51 has the extra passages drilled and functional for creating a vacuum at the shaft end ball bearings. This actually disappeared with the 35/38/40 DCOE1's that used plain bushings on the butterfly shaft ends. Body castings on the DCOE1's were all cast and machined as 40mm, then sleeved and re-bored for the smaller sizes.
FYI. There is very little factory data found anywhere as to changes made with Italian Webers over time. This is why I'm interested in the depth of the main jet cut in your e-tubes. # 51, nor my set has a shallow jet cut for the ball type main jets, and more interesting, none of the original component DCOE1's have shallow cut e-tubes. For function or a collector, the e-tube is a non-collectable, like ball type main jets. They are replacement items, as you have done, only of interest to a Weber restorer, that might be curious as to the variation.
Best, Gordon
 
1 - 11 of 11 Posts
Top