Note to Spectacle wearers (like me): to start with I could not see ANY of the jet sizes on the jets, I thought there were no markings at all. It was only when I used x 5 reading specs AND the "torch" function on my phone that I was able to see them and then photo them - which can't be done close up so have to do at a distance and then crop. All much messing about. 

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Mine is specifically Dellorto DHLA 45C and I have long wondered what the C stands for, so I just found this comment: "This may relate to the C having 6 progression holes and non-C having 3. I can't prove any of this, but this is what I have from stumbling around the internet." Mine DOES have six progression holes, I do not know if others have only three... and from later in that chatter "There seems to be a mismatch, I counted the progression holes, the 45dhla c has 6 holes and the other has 3." so now I know.  They do mention the one with 3 does not have C in its name, just DHLA.

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What I am trying to do here, only started this evening (8/8/24), is to reverse engineer why my carbs have the jets they have and indeed why they are 45s not 40s edit: they are 45s because this is the correct size subject to where the max power band is, but 6,250 to 7,000 rpm indicates 45s not 40s.

Parts explosion 

Venturi is 38 (see image) so barrel required is 38 x 1.25 = 47.5      - Size Available Venturi sizes.  40 24-36mm /  45 28-40mm. /  48 40-43mm

So mine fits with either 45s or 48s - what we have is 45s which i i u c is the better choice - the smallest barrel size for the largest Venturi size.The Venturi size is chosen based on max power rpm mine assumed at 7,000 though probably less than that, if reduced to 36 the choice is still 45s acceptable though 40s become possible. At 6,250 max power the Venturi would be - to be worked out! I do have somewhere a power curve from a rolling road many years ago.

I am not sure about any of this.

This is a photo of my Venturi size 38

assuming descriptions are the same for both Dellorto and Weber here's my check list to find, trailing numbers are from the parts explosion for Dellorto on page 27 of Des Hammill's book in 3rd edition ISBN 978-1-903706-75-6

38mm Choke 1 -checks similar to an example
180 Main Jet 3 -checks similar to an example
150 Air Jet 9 ("Air Correction jet") (or is it 7.50?) -checks similar to an example
7772.5 Emulsion Tube 7 -checks similar to an example
42 Pump Jet 6 possibilities appear to be: .33, .35, .40, .45, .50, .55, .60, .65, .70, .75, or .80 CODE is 7211 and my 42 is not on the list, great.
58 Slow run jet  4 (Idle Jet) -checks similar to an example
xxx Needle valve and seat 11
8010.1 Auxiliary Venturi 2 -checks similar to an example: NOT sure about this as it's off the butterfly not the AuxVenturi body. It seems from here https://www.dellortoshop.com/contents/en-us/p411_8011-Auxiliary-Venturi-for-Dellorto-DHLA45-and-DHLA48-carburetor.html that only 8011.1 and 8011.2 remain available to buy.

https://aircoolednut.com/erkson/ttt/engine/carbs/dellorto.html

doc link provided by Nigel Blandin - THANK YOU! 

It shows the WEBER jetting etc and the first one at 38 is the same as my Dellorto, it also provides a concise list of the jets so I have something to start with in my process to establish what I have page 6.

https://www.caterhamlotus7.club/forums/topic/276230-bdr-and-other-cosworth-motor-specs/?do=findComment&comment=2618386

And here are pics of what they look like from "How to Build & Powertune Weber & Dellorto DCOE, DCO/SP & DHLA Carburettors" ISBN 978-1-903706-75-6 

I have moved these pics here 

https://www.caterhamlotus7.club/blogs/entry/1074-bdr-dellorto-dhla-jets-in-pictures/

because they were making this entry slow and hard to read.

My main Jet: 180 - I changed this from 80 upon spotting a leading 1 in the original jpeg when zoomed in.

Emulsion tube: 7772.5 - I later found the .5 after seeing an example elsewhere.

It's VERY difficult to read these. I am using a set of specs magnification x 5 and a phone then to photo and then crop to capture these. They look worn which surprises me, even after 4 years as there doesn't seem to be anything to wear them.

Air Correction Jet 150 (was 750 but these are usually in a range 100 to 200 so I conclude the 7 is a European 1, for example compare with e 777 above)

Idle Jet - some of my pics, like this one are of TWO of the jets to try and identify their identity numbers clearly, in this case I concluded it is 58

Auxiliary Venturi 8010.1

Pump Jet 42

So in the process of working on the above I have identified several springs I wish to replace in line with my policy of replacing all rubber and spring components, not least as I now know from the first round of doing this that over 40 years rubber goes hard and springs stretch, which compromises the design intentions for both. For example I am hoping the accelerator response to "foot off" becomes more snappy than currently. Likewise the carb/inlet manifold seal is truly airtight (which it may or I suspect not be). Whether to remove and reset the inlet manifold is an open question.

Here's the list of bits, notably there is the venturi choke and the choke choke (the cold start choke) and one simply has to know which is which. I do use it and propose to continue to do so because while it can be tuned to start without it, that affects the idle emissions which is where this little project started, to see how close to modern cars one can get with carbs. What has become clear is the principal requirement is endless patience.

https://www.dellortoshop.com/contents/en-us/d2804_Dellorto-DHLA-carburetor-parts.html

I find this site expensive, more reasonably place sources welcome. The above order took several hours going through nine pages of parts as a check list. I had thought it was all springs, but there are only three and the rest is refurbing the cold start choke mechanism.