DELLORTO QUESTION

[types26/36]

I have three sets of Dellorto carbs, one set are DHLA 40, one set DHLA 40H and one set of DHLA 40G.
While cleaning and checking I mixed up the idle jet holders and they appear different as some have an extra hole below the threads ....see picture, can anyone tell me which jet holder go in which carbs?
And another question, one of the emulsion tubes appears to have had the raised section machined down....any idea why anyone would do that and what effect it would have?

[Esprit2]

Brian,

The idle jet holders and emulsion tubes should be matched pairs in one carb set. I don't know what's going on with the one that is a smaller diameter, but something is not right.

Are the part numbers still present on the idle jet holders and emulsion tubes? (They should all be stamped with numbers). Are the carbs for specific engines you have, or are they strays you purchased somewhere like eBay and plan to use on a Lotus Twin Cam? The H and G models were not used on the Twin Cam, so they must be from something else (I believe the 40H is an Alfa carb).

The final idle jet holder, emulsion tube and jet selection is specific to the engine application, not to the carb body/ model number. If you're rebuilding the carbs to go back onto the running engines they originally came from, then it's important to know what went where. But if they are eBay-finds you hope to install on a twink, then disregard the old bits and refer to the Lotus manual for the correct bits you need to install... at least as a starting point.

Dellorto Idle Jet Holders (Idle Air Corrector Jets) are not numbered sequentially; rather, they're numbered totally randomly. Don't make any assumptions about which one is the next size richer or leaner.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[types26/36]

Tim, thanks for the reply, the idle jet holders are matched i.e. I have 12.....and three sets of carbs, four with the extra holes and eight without the extra holes, I had just shown the two different types in the same picture as I was trying to ascertain which carbs each set belonged too as I had mixed them up by mistake.
The DHLA 40's are the originals from my Sprint but I have been running the 40H's for a long time, the 40H's & 40G's are emission carbs from Alfa's and I intended to refit the original DHLA 40 (non emission) back on but just got the jets mixed up.
A friend has since emailed me to say his non emission DHLA 40's have the idle holders with the extra hole so that is sorted.
The emulsion tube is a different thing, only one has been machined and I cant understand why although I cant see it could make any difference anyway.
POST EDITED

[Esprit2]

Tim, thanks for the reply, the idle jet holder are matched i.e. I have six.....and three sets of carbs, two with the extra holes and four with out the extra holes... (Snip)...

Brian,
No, they're not matched. The fact that one has an extra hole illustrates that they're not matched. See the attached photo of the idle jet holder line-up (click on the image to enlarge), and you'll see that they vary in the number, size and location of holes. That's what makes them different, and that's why I asked if all yours still have the part numbers stamped on them. The differences between some are subtle and can escape the eye, so go by the numbers.

So, the question is still on the table. Are the numbers still stamped on the parts, and do they match?

A friend has since emailed me to say his non emission Dellorto 40's have the idle holders with the extra hole so that is sorted.

I don't think it's sorted. Again, look at the photo and you'll see that several idle jet holders have an hole below the threads. It's not enough to go by the presence of a hole there, it needs to be the right size hole in exactly the right location. Sorry if it sounds like I'm beating a dead horse here, but go by the numbers stamped on the parts.

The emulsion tubes are a different thing, only one has been machined and I cant understand why although I cant see it could make any difference anyway.

It makes a big difference, even more important than the idle jet holders. The Emulsion tubes are the heart of the carbs, and the differences between them are even more subtle and prone to black magic. That one oddball tube isn't subtly different, it's grossly different.

Install a matched set with the proper part numbers stamped on them as called for by the Lotus Elan manual. I'm not BS'ing you. This is important to getting the carbs running correctly.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[types26/36]

Sorry Tim I am misleading you, I should have said I had 12 idle jet holders all together....four for each set of carbs, the four with the extra hole are all marked with 7850.2 .....a matched set.
The other eight have no markings but all appear to be the same......two sets of four as they all came out of the carbs.
I have 12 Emulsion tubes .....(three sets of four) the only mis-match is the E.Tube that has been machined down although all the numbers match on them, what effect will the machined down one cause?
Sorry for the confusion, ......too many carbs and jets laid around, have not even started on my six sets of Webers!

[elansprint71]

... and thus was fuel injection invented....

[Esprit2]

... and thus was fuel injection invented....

Fuel injection has it's own rats nest. Same but different.

Tim

[Esprit2]

Brian,

I posted (or I thought I posted) a reply, but it disappeared into the ether. I wonder what I wrote that was so brilliant?

I should have said I had 12 idle jet holders all together....four for each set of carbs, the four with the extra hole are all marked with 7850.2 .....a matched set. The other eight have no markings but all appear to be the same......two sets of four as they all came out of the carbs.

7850-2 is about right for a Lotus Twin Cam. That's what the Europa Twin Cam used, but my Elan (Dellorto) manual is out on load so I can't verify the Elan uses the same holder.

In addition, 7850-2 is the second most rich idle jet holder, and I doubt that it would have been used in an emissions carb since they were generally jetted lean. Since you indicate the 40H and 40G are emissions carbs, the 7850-2 holder probably didn't come from one of them.

Dellorto models with a suffix letter, like 40H & 40G, are generally carbs built for OEM applications. Carbs that are purchased by the thousands and all jetted the same. Often, the jets & bits inside them are unmarked since they're all supposed to be identical anyway. Some go so far as to not even have replaceable jets. The holes are direct-drilled into the body, or one-piece versions of the assemblies are pressed in instead of screwed in.

Suffix letter models can often be had for a pretty cheap price, but much of the savings typically goes back into completely re-jetting them for your application.

I have 12 Emulsion tubes .....(three sets of four) the only mis-match is the E.Tube that has been machined down although all the numbers match on them, what effect will the machined down one cause?

The config differences across the range of emulsion tubes are often subtle, yet they still make enough difference to cause problems for tuners. That one oddball tube is different by a lot, and there's nothing subtle about it. I don't know specifically what affect that missing shoulder will have, other than the mixture in that throat will be different. I just know I wouldn't try to use it.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)