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| Dellorto Troubles | Rating: 
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| Posted: 05-23-2005 03:08 pm |
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1st Post |
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Brett Gibson JH5 20497 Member
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Help, I’m still having Dellorto troubles and they are turning into nothing but a frustrating money pit that am about to give up on, and that really annoys me because I don’t normally like to throw in the towel. History: I picked up a set of Dellorto 40’s along with the manifold from England that were fitted to a JH over there, the jetting was factory stock so in my ignorance of Dell’s I thought they would work on my car due to it being a stock engine. First thing I did was purchase rebuild kits, air cleaners, gaskets and hoses plus the linkage, then I stripped the carbs down and soaked them in a good quality carb solution overnight, I cleaned up and blew out all the passages and jets and made every thing spic and span, then I put them back together with all the new gaskets and O-rings, made a couple of silly mistakes, forgot to put O-rings back on the idle emulsion tubes and put the choke piston in the wrong way around so that it was on choke when it was supposed to be off, took care of that though. Then I stripped the Stromberg’s off the car and modified the distributor, I removed the vacuum advance mechanism and locked the plate, and I use a flamethrower coil, 8 mm wires, NGK plugs, and an Allison electronic ignition, and the timing is 10 to 12 degrees advanced. Once I fitted the Dell’s and got things running at idle they seemed fine but would pop and spit back under fast acceleration from 1000 to 3000 range, high RPM’s seemed fine, this is all taking place in the garage no road testing yet, well I made an earlier post and received some very helpful info on this problem it was recommended that I change some of my jetting, so here’s what I had and what I changed to, new old 40 Carb Size 33 35 Choke Size 7848.1 Venturi 145 130 Main Jet 7772.5 Main Jet Emulsion Tube 190 160 Main Jet Air Correction Jet 55 Idle Jet 7850.7 7850.5 Idle Jet Holder 45 Pump Jet 70 Cold Start Jet 7482.1 Cold Start Emulsion Tube 7298.2 Float Assembly 7481.2 Butter Flys The new chokes and items have reduced the popping and spitting but not eliminated it, my plugs still are very black and I get some exhaust pops and a little black smoke, all saying to rich, but I’m told to stop Dell’s from popping that I need to run richer. I have tried a number of different ways to try and tune them in, first removing two plug wires and adjusting the mixture one carb at a time but that doesn’t seem to have any effect, then the other by hooking up a 4 vacuum gauge unit one to each carb and adjusting the mixture and air by pass screw to try and get the same across all, #4 cylinder always appears to be pulling more vac?? Still NG, then as with Strombers checking the air draw thru the barrel of the crab’s with a Uni-sycn type device and again the readings are all over and hard to get even close to each other, even trying all this it still pops and seems to rich. I’ve looked over the carb schematic checking to see I didn’t forget some thing the only difference I can find is that I don’t have the spring/filter in the pump jets but I was told by JAE that it was not necessary, so right now I have taken the crab’s apart again cleaning and blowing out everything and tonight I will put it all back again and give it one more try, any and all suggestions would be greatly welcome like I said I don’t like to give up but in order to get to drive my car and hopefully make the East Coast Nationals I going to have to put the Stromberg’s back on if I cant get this settled ASAP. Thanks for reading all this. Cheer’s Brett PS. I have good compression on all cylinders.
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| Posted: 05-23-2005 03:54 pm |
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2nd Post |
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Brian Kelly Member
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Brett, A couple of things. I’m running 45’s and by no means am an expert. But I can share some of my experience. Idle holder size 7850.# (# = Lean- 5,10,9,4,1,3,6,7,2,8, -Rich). You’ve gone from .5 (lean) to .7 (richer – but a good choice) so now you’ll need to reduce your idle jets which makes sense (black plugs) to lean out the mix. You may have noticed that the .7 has smaller dia cross drilled holes. These holes allow air into the mix – smaller holes, less air, richer mix. Also, JAE sells a Lotus part – an anti-popping valve (not sure of the name) that goes in between the carb and the manifold. They’re not too expensive and in my case eliminated the popping. I use a Morgan CarbTune to balance mine. If you’re serious about using these carbs you’re going to need a better tool for balancing. The uni-sync won’t do the job since it restricts the air flow into the carb. With the Morgan or a 4 tube mercury manometer you can read the vacuum on all 4 cylinders at once and be able to compare. To adjust the needles pull two plug wires and adjust needles on one carb at a time for highest engine idle. Then reverse and adjust the other carb. Also, one by-pass screw on each carb should be closed and the other opened just enough to balance the two barrels to each other. Once you have the two barrels one each carb balanced to each other then use the balancing screw between the carbs to balance the carbs to each other. I hope this makes sense. Brian
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| Posted: 05-23-2005 04:52 pm |
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3rd Post |
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JASPER Member 
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I second Brians advice - My 40mm Dellortos used to spit and pop - I added the anti popping spacers from JAE and solved the problem - They only hiss and pop now when the choke is on - or if the idle is too low - The MORGAN CARB TUNE II is the only way to go to properly tune them in - not cheap at about $150 but well worth it - It's also possible tht your main jets are worn out ? New ones are available but somewhat expensive - Don't give up on them - once you've got them running right all will seem right with the world !! Nothing like running Dellotos on a 907 ! cheers James
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| Posted: 05-24-2005 03:26 am |
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4th Post |
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Jim Ketcham Member
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Brett, Your jetting seems pretty good to me. I am running 45s in my 2.0 with essentially that jetting and am not having any problem. What concerns me is the lack of response of your mixture screws. The only time this happened to me is when I had an air leak at the manifold. Another symptom of that is erratic manometer readings between the barrels of the carbs. I use a Motion Pro 4 tube mercury manometer and am very pleased with it. It is available for $34.00 plus shipping which I think is quite a bargain. Here's the link of the place I got mine if you are interested: http://www.mawonline.com/motion_p.htm Good luck, Jim
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| Posted: 05-24-2005 02:52 pm |
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5th Post |
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Brett Gibson JH5 20497 Member
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Thanks Guy's I appreciate the input and knowledge you are willing to sharing with me, it seem's my 4 vacuum gauge setup just wont make it in this situation and definately the Uni-syn style tool wont, the Morgan Carbtune is a good chunk of change and probably worth it and it was very good to see that there are cheaper alternative's as well, looks like I'll be needing one of those. Brian if I understand you correctly I need to use smaller idle jets, most people recommend the 55's which is what I have, to go smaller though would I go to 60's or 45's not sure which way they run, I also see that the anti-popping thingy's are a must. As Jim suggest's I will go thru and check for air leaks and give it one more shot with what I have now, if that does'nt do the trick I'm afraid that I am just going to have to pull them off for this year and try again next, I've already over spent my JH budget for this year, not to mention the time it's taken to get this far, plus If "she who must be obeyed" catch's on I'm in the dog house. But believe me I will get these things going, it just does'nt look like it will take place now. Thanks for all the help Brett.
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| Posted: 05-24-2005 02:55 pm |
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6th Post |
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Jensen Healey Super Moderator 
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Do you have Des Hammill's book? It was key in my battle with the Dellortos. You mentioned an Allison ignition. I had a Crane Cams (same as Allison) optical unit on my car. It hit one of the bumps on the inside of the distributor cap and was pushed to the side causing a phasing problem. This means the rotor is not pointed at the tower on the cap when the coil fires. It leaves carbon tracking inside the cap which looks like ferns drawn with a pencil. You need a bright light to see them. You get a weak spark that leaves black crap on the plugs. Start the car after dark and look for a fireworks show. If you have none, ignore this paragraph. Install new plugs. Trying to tune a car with fouled plugs is a waste of time. I use Autolite 64's because they are cheap and work great. The Dells adjustment screws are a very fine adjustment and won't change the air-fuel mixture very much. Turn them in until they seat lightly and back off 4 turns. Do not adjust them without a 4 tube manometer. You can get a mercury version at your local motorcycle shop for $40 and it has the correct fittings for the Dells. The less toxic manometers cost more. Balancing each carb involves making the stronger barrel run worse! Use the manometer to adjust each barrel for maximum vacuum and then open the bypass on the stronger barrel until it matches the weaker one. Do this for each carb and then adjust the linkage until the manometer is even across all four barrels. I tuned mine at idle and then gently increased the rpm to 3000 being careful not to suck the mercury into the engine. I re-adjusted slightly for best average of the two readings, a little worse at idle but a little better at 3000 rpm. I used a dab of silicone so the screws would not rotate due to vibration. There is a good write-up on this procedure by Tim located at: http://groups.yahoo.com/group/S1S2S3owners/files/Dellorto%20jetting/ You have to join Yahoo groups to view the file. Now take your car to the local smog station and get a pre-test. Use the CO reading to determine if you are weak or rich. Shoot for about 2%. Installing Dellortos is not for the timid. It took me 6 months to learn, digest and do the tuning. If you stick with it you will be very happy with the results. Kurt P.S. Don't change the idle jets unless you know you are running lean. The emulsion tubes are the fine tune between each jet size. EDIT It took me a while learn where the bypass (bleed) screws are. Not all carbs have the exact look or configuration. Check the diagram at http://www.dellorto.com Last edited on 05-25-2005 03:32 pm by Jensen Healey |
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| Posted: 05-24-2005 05:28 pm |
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7th Post |
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Greg Fletcher Administrator 
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I also think your new settings look good. This what I've been using on the new Dellorto carb kits with for a 2 liter engine that we sell in the Club Store: Choke .............................. 34 mm Main Jet .......................... 145 Main Air Corrector Jet ... 190 Main Emulsion Tube ...... 7772.8 Idle Jet ............................. 55 Float Needle Valve ......... 170 Pump Jet .......................... 45 Starter Jet ......................... 60 Note: 34mm are used instead of 33mm and the main emulsion tube is now 7772.8 as 33mm and 7772.5 are no longer available as new parts, these make virtually no difference in the overall settings however. I have to say, an overnight soaking in carb cleaner may not be enough to clean out an old, ex-UK set of Dellortos. These things can get pretty terrible over time and the varnish built up can be work to remove. The carb cleaners and soaking agents they sell at the auto parts stores these days are nothing compared to the deadly, yet highly effective cleaners from years ago. As much trouble as a Dellorto conversion can be, it is a great upgrade, especially with a performance/2.2 engine. Your patience will rewarded later on down the road.
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| Posted: 05-28-2005 02:14 pm |
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8th Post |
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Dave Member
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How about aloaner carb tune that makes the rounds......?
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| Posted: 05-29-2005 05:52 pm |
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9th Post |
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Jensen Healey Super Moderator
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Hey Brett, How's the tuning going? give us an update. All this talk got me excited and I got out the manometer and balanced the Dellortos again. The engine is smoother but seems to lack the punch it had prior to the tuning. While reading the balancing procedure again at http://www.dellorto.com I saw this: "With the No 1 cylinder blow-by pipe temporarily clamped shut, all readings should be brought to the same level. Unclamped for normal running, No 1 cylinder’s mercury level will always be lower than the other three cylinder levels." Do the DHLA 40E's have this blow-by pipe? If so where is it? Kurt
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| Posted: 05-31-2005 12:09 pm |
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10th Post |
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Brett Gibson JH5 20497 Member
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Kurt, Yea I read that about the blow by pipe but I dont have a clue as to what it means, I dont see anything on the Carb that looks like I could clamp it off. Alas for an update on how things are going, well I'm sad to say I pulled the Dell's off and switched back to the Stromberg's, when I intially took the Strom's off I did'nt do anything that could'nt be undone just in case .................. so I had the car back up and running for the weekend in no time at all, what really clenched it for me was I stripped the Dell's down cleaned them up agian for the unpteenth time, installed new plugs, and took the car for a run, all seem right, no popping spitting back, stall or anything it felt great for about 5 to 7 miles then the same old crap started up again, that was it, so I figure now I will just pick up the anti-popping thingies and the other book on Dell rebuilding I dont have, ( Dell Slaven's) buy a Manometer and strip them down and let them soak for a week or so in carb cleaner, and towards the end of this driving season maybe try fitting them again. Thanks to all who responded for try to help me out I really do appreciate it, I have'nt given up and I will get these thing's to work it's just I want to drive the car to the Nationals this year and the Dells just did'nt give me a "warm and Fuzzy" feeling. Thanks Brett.
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| Posted: 05-23-2006 12:58 pm |
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11th Post |
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bertw Member
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I am having very similar problems with Dellorto carb spitting as mentioned in this thread, can anyone please provide some info about these 'anti-spitting' devices as I'd like to know a bit more. Many Thanks.
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| Posted: 05-23-2006 02:47 pm |
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12th Post |
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Brett Gibson JH5 20497 Member
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Yes, I picked a set up from "Dave Bean" all they are is the mounting plate that is between the manifold and carb body, the plate that has the O-rings in it, only it has a little bit of a cone to the inside edge on one side (1/4"), the side to the manifold, it's supposed to help the air flow and reduce the spit back, dont know as yet if it will because I have'nt put the Dell's back on yet, there still soaking in solution, 4 weeks so far, I think they cost about $60 for all four if memory serve's me correctly. Has anyone actually used them ??? Brett.
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| Posted: 05-23-2006 04:10 pm |
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13th Post |
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Brian Kelly Member
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I've got them installed on mine and they seem to work. I've had no popping since they were installed a few years back. I even forgot they were in there untill now. Hummm, I wonder what else I've installed and forgot about? Brian
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| Posted: 05-23-2006 07:50 pm |
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14th Post |
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John Kimbrough Member
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Brett, I noticed in your first post that besides changing to Dells, you also changed to a Pertronix and Flamethrower. When I did this my car would not run more than a few miles before quitting. Each time I checked, the plugs were blackened. What I found was that with the Flamethrower, the spark plug gap needs to be opened substantially or the spark will not satisfactorily form and the cylinder will misfire and then quit firing at all. Since I widened the gap, the problem has disappeared. See my web site on home.comcast.net/~jrkengr2/ for complete details. For the spitback problems I enriched the mains which provide the mixture in the 2-3000 rpm range through the progression holes. With Dell 45s I have no more spit back and no more plug fouling.
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| Posted: 05-24-2006 09:25 am |
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15th Post |
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bertw Member
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My problem is very similar to that which Brett described in the first message on this thread i.e. the plug colour indicates the mixture is too rich but have been recomended to run richer to stop the popping. I tried running it richer but the engine coked-up and I had to de-coke it (no surprise there) so I need to sort it some other way, hence my interested in the anti-spitting/popping device. I can't find any reference to it on the internet, could someone please send me a URL/link so that I can find out more and/or send me details about where I can purchase one. Many thanks - Bert (in the UK)
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| Posted: 05-24-2006 01:45 pm |
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16th Post |
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Brian Kelly Member
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Like I said the Lotus anti-poping plates did it for me. In addition I’d like to recommend using a "colortune" spark plug to actually tune the carbs. It is basically a spark plug with clear (glass?) insulator which when installed and engine running allows you to look into the cylinder and see the flame color. It is truly an amazing tool. I was surprised to see a bright orange flame at idle and progression which turned blue-ish during the main (higher rpm). Ideally you want to see light blue (Bunsen burner blue). I’m working through it now and am putting smaller jets in. I’m struggling with trying to get decent gas mileage out of mine. My engine and cams have been modified quite a bit so I’m not sure I’ll get much better than the 18 mpg I’m getting around town. Also there is a great eBay seller of Dellorto jets (Alfa….something) in Italy that has great prices on all the jets, holders…. Just email him. I’ll try to post some photos of the Colortune in action. Also, another must have is the Morgan Carbtune for balancing. A bit Pricy but worth the cost in my opinion. My wife likes it too since she is convinced that all this stuff keeps me out of the pubs at night! Brian
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| Posted: 05-24-2006 08:50 pm |
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17th Post |
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Ron Earp Member 
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Brian, where did you get a set of those plugs? That would be quite useful I think for some diagnostic purposes. Best, Ron
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| Posted: 05-25-2006 01:39 pm |
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18th Post |
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Brian Kelly Member
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Hello Ron, I bought one off EBay. When you see the price you may just want to buy only one. They go for $50-$60 each. I just move the one from cyl. to cyl. I was reading a rather interesting article on their use. The author installed the colortune and had the rear (drive) axle up on jack stands so the tires could spin freely. With the tranny in gear a second person pushed the gas peddle and applied the brakes at the same time there by loading the engine. This way the combustion flame could be viewed with the engine under load. The author actually wrote that they would run engine near full throttle with the brake applied for brief periods. Just long enough to see the flame color. It’s kind of a poor man’s dyno. I haven’t tried this method yet. I’ve been busy fixing up a 94 Saab for my Son. So I’ve had grease under the fingernails just not the Jensen kind. Brian Here is one link to a seller. http://www.international-auto.com/index.cfm/fa/p/pid/3448/sc/8189 Last edited on 05-25-2006 01:41 pm by Brian Kelly |
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| Posted: 05-25-2006 03:31 pm |
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19th Post |
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Ron Earp Member
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That is a damn good idea! My racing partners and I were having an email discussion of using these things yesterday and we all sort of come to the conclusion that without load it'd be rather useless except at idle. I thought of using a long liquid filled liqht guide to see the plug while in the car, a piece of technology I have access to at work. We didn't think of jacking and using a brake! Might do that. Still like dynos much better, but I think one of these could be made to work pretty well using the brake idea. R
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| Posted: 05-25-2006 04:55 pm |
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20th Post |
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Brett Gibson JH5 20497 Member
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Ron & Brian, I tried using a Color-Tune one time and didnt have to good of luck, not sure if it was my setup or what, (Strombergs) but in adjusting the mixture I didnt get much of a color change, it showed a blue flame from full rich to lean, maybe it works better on Dellorto's. Brett.
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