17 replies to this topic

[NRoshier]

Weber seem to have followed Dellorto's lead with extended length (full length of the carb body) Aux venturis in their 45mm DCOE carbs. I have picked up a set of 45 DCOE model 150 5B with these extended venturi's but no one seems to be able to identify which venturi it is or tell me why these were used.
It has been suggested that an extended aux venturi means that the main circuit starts sooner, but can anyone shed some light on this?

[275 GTB-4]

Try here....http://www.racetep.com/webjettune.html

[NRoshier]

thank you, I have been there and have some tuning books, none of which show the longer Aux venturi's. A thorough Google has not shown any plausable information: naturally I would try this before posting here.

[McGuire]

Originally posted by NRoshier
Weber seem to have followed Dellorto's lead with extended length (full length of the carb body) Aux venturis in their 45mm DCOE carbs. I have picked up a set of 45 DCOE model 150 5B with these extended venturi's but no one seems to be able to identify which venturi it is or tell me why these were used.
It has been suggested that an extended aux venturi means that the main circuit starts sooner, but can anyone shed some light on this?

If I am following your description correctly, those are the long-style, anti-reversion auxiliary venturis (to prevent fuel stand-off). Apart from their length the sizes run the same as the short ones, 3.0 through 5.0 or so. Typically found on IDA Webers.

[NRoshier]

I will post an image, it will be easier than trying to describe them.

[McGuire]

Do the auxiliary venturis extend up to the bells of the air horns, like this?

[NRoshier]

No they don't, I have seen the extended IDA aux venturis before.
These are like this:

[McGuire]

Those look like the 40DCOE-style auxiliary venturis. What size are the throttles?

[NRoshier]

45mm, the carbs are marked 45DCOE 150 5B.
I know they look like 40 and 42mm DCOE, but they are 45mm.

[McGuire]

Then apparently the 45 has been made in both styles. Of the two this one is probably superior -- the other style tends to work loose.

[NRoshier]

Thanks for that. the tricky thing is that there are no markings of any kind on it, so I have no idea what size it is.
BTW how did you go with Repco?

[McGuire]

Just curious...how are the air horns attached?

[scooperman]

MED Engineering has been selling an interesting inlet for DCOE Webers, see pic at...

http://www.med-engin...93&vlang_id=237

Looks like a fairly normal stub stack, plus a centered velocity stack for the aux venturi. I guess the idea is to be bring in the main circuit earlier.

[cosworth bdg]

Originally posted by NRoshier
Thanks for that. the tricky thing is that there are no markings of any kind on it, so I have no idea what size it is.
BTW how did you go with Repco?

Repco what??????????????????

[zac510]

Originally posted by scooperman
MED Engineering has been selling an interesting inlet for DCOE Webers, see pic at...

http://www.med-engin...93&vlang_id=237

Looks like a fairly normal stub stack, plus a centered velocity stack for the aux venturi. I guess the idea is to be bring in the main circuit earlier.

Wouldn't a well sized choke/ram tube provide a similar result?

[McGuire]

Originally posted by NRoshier
Thanks for that. the tricky thing is that there are no markings of any kind on it, so I have no idea what size it is.

The markings can be faint or nonexistent. Or possibly the parts were media tumbled at some point in their career, which will polish them off nicely.

Folks are probably wondering what in blazes we are going on about with these different types of auxiliary venturis. Well, when one disassembles a 45DCOE one would expect to find this style...





but instead, your carbs have the type usually found in 40 or 42 DCOEs, or in IDA's etc. I guess one should never be too terribly surprised at one may find inside a Weber, as they have been manufactured (and modified) in near-infinite variety.

At first I thought you might be talking about this flavor of auxiliary venturi, the "anti-reversion" type, which is available in most venturi "styles." Hey, note: the numbers are legible here (4.5) and not legible in the upper photo...

[NRoshier]

true, the more I have to do with Italian engineering the less surprised I am by the small un-announced changes. I have a siple reason to want to find out about them i.e. that if I have to pay $90 per hour to tune the things than I want to be sure that what I hand over has no surprises. It may be simpler to sell them and get new ones.

[Gerr]

Originally posted by NRoshier
No they don't, I have seen the extended IDA aux venturis before.
These are like this:

Those are similar to, if not the same as the auxilary venturis (part number 7715) supplied in the 45 DCOE 14. Used on the Alfa Romeo Guilia TI Super.