anthonym Posted October 14, 2023 Share Posted October 14, 2023 I am busy tuning and fettling my twin Dellorto DHLA 45s doing things like Balancing with Carbtune Pro, fixing float levels and such like. My current exploration is how to fix my accelerator pumps which seem to be inoperative, one leaks (both barrels) and I suspect the 5mm gap at the end of the push rod is "missing", but that looks like I may have to remove the carbs from the car to fix and if removed to service the pump mechanisms (i.e. x 2). Purpose of my post here is to see if anyone else is interested in these sorts of things? Or even has experience of same. All first time for me. My carbs have been refurbished, but this was 9 years ago and only brought in to use relatively recently (a year maybe).So ball bearings "stuck" are possible etc. My sources of reference are google, many web sites, youtube and the book 3rd edition of SpeedPro "How to Build & Power tune Weber & Dellorto ..... DHLA Catburettors". I can't find any version of the Dellorto Tech book even in pdf anywhere. I also have contact with "my" carb refurbisher who seems to remember me. My previous owner/builder (r.i.p. 2018 age 90) assured me in about 2003 the jetting is perfect so I have no intention of changing any jets. Sounds like main jet "34" is ideal for my 1987 1700 BDR on standard 169bhp.The Speedpro book is hard work because it combines both Weber and Dellorto in the same texts - and avoids discussion of setting the length of the accelerator pump drive pole saying " do not touch".So, anyone like to play this game? Sandpit now open.(Do we have an index of all Dellorto DHLA chat on here? Answer is no not really.)The carb balancing has also greatly improved the overheating problem as they were very (very) un balanced.Anthonyare we in site transition yet I wonder? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 14, 2023 Member Share Posted October 14, 2023 "Do we have an index of all Dellorto DHLA chat on here? ":https://duckduckgo.com/?q=site:caterhamlotus7.club+dellorto+dhlaJonathan Link to comment Share on other sites More sharing options...
anthonym Posted October 14, 2023 Author Share Posted October 14, 2023 thanks Jonathan, but that mostly hits my own posts, so not really what I meant about an "index", I have tried that and much else besides (for each detailed aspect I have worked upon), so we are here looking for other enthusiasts with similar interests as "we" seem to be limited in number. - anthonyedit: in any case I have added that search to my op. Link to comment Share on other sites More sharing options...
Wrightpayne Posted October 14, 2023 Share Posted October 14, 2023 DHLAs - thats an unusual fitment - factory fit or later modification? Link to comment Share on other sites More sharing options...
anthonym Posted October 14, 2023 Author Share Posted October 14, 2023 That's an interesting question. As far as I know it was included in the self-build from a CKD Kit. (Completely Knocked Down). Our most excellent archivist recently found my car's Purchase order; I'll have a look. So, no sign of the engine which he told me he bought direct from Cosworth with some mods he wanted. (I am since told buying from Cosworth direct was not possible; maybe an engine builder who was trading as if Cosworth.. or whatever.) The Dellortos were on the car and he spoke as if they had always been there from the start. I found the CC Pro Forma invoice, but engine not included, though of great interest to me in my provenance search, Edit: it wasn't "sold as a BDR", it was sold as a "de-dion starter kit CKD" including BDR Cooling system, BDR exhaust , but not VIN recorded as an HPC because (a) not factory built and (b) engine not supplied by CC.BDR1700 price list 1987-1.pdfThe 1987 BDR basic spec, I see Weber 45s which explains why my Dellortos are 45s when these days I am told these are "too big". Reading the book above says the Dellortos have a slight edge over Webers in terms of tunability at that time, and my builder told me he spent years tweaking jets so presumably he enjoyed and chose this choice as it were. Great question, thanks.BDR1700 price list 1987-1.pdflunch calls :-)Anthony Link to comment Share on other sites More sharing options...
anthonym Posted October 14, 2023 Author Share Posted October 14, 2023 and max power at 6,500 - I agree ;-) Link to comment Share on other sites More sharing options...
anthonym Posted October 14, 2023 Author Share Posted October 14, 2023 OK now I understand why there is no or very little Dellorto chat on here; the factory supplied Webers for both factory and kit builds. Link to comment Share on other sites More sharing options...
anthonym Posted October 14, 2023 Author Share Posted October 14, 2023 thank you to both respondents - anthonyI may add by edit in here future external links since BC has so little.https://www.caterhamlotus7.club/forum/techtalk/dellorto-dhla-45s-leaking-both-pump-jets-front-carb?page=0https://www.thelotusforums.com/forums/topic/37276-dellorto-accelerator-jet/https://sideways-technologies.co.uk/forums/index.php?/topic/1048-setting-dhla-dellorto-dellorto-float-fuel-level/ Link to comment Share on other sites More sharing options...
Gridgway Posted October 18, 2023 Share Posted October 18, 2023 Interestingly my new to be BDR project car has Dellortos so I am interested in the topic. I am planning on supplying them with fuel over the weekend for the first time since 2008 when the car was last used. I'm expecting a leak or two! I've refurbed the fuel supply system, so at least that should be ok! Link to comment Share on other sites More sharing options...
Gridgway Posted October 22, 2023 Share Posted October 22, 2023 Quick update from me. With a refreshed fuel system (new tank, facet pump fixed, malpassi regulator refurbed, a pressure gauge added and new hose all through) I powered it up and although it took the pump a little while I got nice pressure - too high initially, but regulated down to 3.5psi. No leaks, all good. I expected that the plumbing would be ok, but expected that the Dellortos might leak. But they didn't. In fact no sign of fuel at all from them. I pumped the throttle a few times, but no squirts and no smell of fuel at all. I'll do a bit more diagnostic work, to find out why, but I suspect the best thing to do is to get them professionally refurbed. I used Paul at Weber Carb Reconditioning Services for my Webers a couple of years back and he did a very good job. Link to comment Share on other sites More sharing options...
OldAndrewE Posted October 22, 2023 Share Posted October 22, 2023 Graham, did the float chambers fill up? Link to comment Share on other sites More sharing options...
Gridgway Posted October 22, 2023 Share Posted October 22, 2023 I had to finish up so didn't investigate further. I will have to find the float chambers to see. It does seem to be a starting point if the needle valves are jammed. Some research to do! Link to comment Share on other sites More sharing options...
Gridgway Posted October 22, 2023 Share Posted October 22, 2023 They have got the awkward throttle mechanism on top which is a bit of a pain, so I only checked one, but yes it has fuel in the float chamber. I have no idea of the internal plumbing yet - ie how the fuel gets out of the float chamber, but that could be blocked. Link to comment Share on other sites More sharing options...
Gridgway Posted October 22, 2023 Share Posted October 22, 2023 So just thinking it through, would you expect to see any fuel just opening the throttle with no airflow going in? Should you get a squirt of fuel from the accelerator pump? Link to comment Share on other sites More sharing options...
anthonym Posted October 22, 2023 Author Share Posted October 22, 2023 yes if you do it hard enough (and after sufficient pumps for the pump diaphragm to be full) - just fixed mine that were completely inoperative. Link to comment Share on other sites More sharing options...
anthonym Posted October 22, 2023 Author Share Posted October 22, 2023 fuel pressure should be 1.5 to 2 psi from my searches. Link to comment Share on other sites More sharing options...
anthonym Posted October 22, 2023 Author Share Posted October 22, 2023 (edited) SORRY I am playing ctahc up here: " first time since 2008" that means certain bits can be expected to be clogged shut. Specifically the ball bearings in the accelerator pump delivery jets x 2 . And the ball bearing in the accelerator pump diaphragm two way "jet". Edited October 22, 2023 by anthonym Link to comment Share on other sites More sharing options...
anthonym Posted October 22, 2023 Author Share Posted October 22, 2023 That "Paul" sounds like the same chap who refurbished my Dellortos, which although only recently brought in to use, was now many (2014?) years ago, he has very kindly been guiding me in my current "service" work to counter the effects of non use while the rest of the car was being rebuilt. I will be replacing the regulator to match yours very soon, to have the pressure info. Link to comment Share on other sites More sharing options...
Gridgway Posted October 22, 2023 Share Posted October 22, 2023 1 minute ago, anthonym said: SORRY I am playing ctahc up here: " first time since 2008" that means certain bits can be expected to be clogged shut. Specifically the ball bearings in the accelerator pump delivery jets x 2 . And the ball bearing in the accelerator pump diaphragm two way "jet". That's why I think the best thing would be to get them professionally refurbed. I don't have the time to do it myself. I don't have the knowledge either, but it's all learnable (once I have progressed past a PhD) Link to comment Share on other sites More sharing options...
anthonym Posted October 22, 2023 Author Share Posted October 22, 2023 (edited) oh yes PHD PLUS 🙂 It's easy working on the refurbed carbs, if an unexpected adventure. I have tons of pics and videos I made to remind myself. Very satisfying to get them working nicely tuned - Paul can't tune them off the car. edit: all I did was take them to bits and blast them with an airline. Getting the floats right I have done in theory, but want to prove it using an external pair of float chambers. That means 27mm from the top of the chamber to the fuel at cut-off point - whereas 15mm from float to roof is the official measure intended to achieve the 27mm., Getting them off involves trickery so shout if you do. edit: assuming same as mine and mine was kit built. edit: everything is easy to get at except (of course) the accelerator pump system, which forced me to dismount the carbs (my greatest fear) because the refit requires the 4 fixing nuts per carb to NOT be too tight. Edit no fuel at all? I'd first check the integrated fuel filters, the big shiny nut under each fuel hose entry point. 30 seconds work. I THINK I read that the fuel shut off valves operated by the floats can seize if not used.. I think, in which case straight off to Paul to refurb, if not anyway. Edited October 22, 2023 by anthonym PICTURE ADDED for curiosity Link to comment Share on other sites More sharing options...
anthonym Posted October 25, 2023 Author Share Posted October 25, 2023 On 22/10/2023 at 23:06, anthonym said: fuel pressure should be 1.5 to 2 psi from my searches. Fuel pressure now reduced from 3 psi to just under 2 psi (so it was 50% too high) with install of this: next is to tune again using the manometer. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted October 29, 2023 Leadership Team Share Posted October 29, 2023 Link to comment Share on other sites More sharing options...
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