ChrisV Posted January 30, 2015 Share Posted January 30, 2015 Hello, I have encountered a lot of problems the past year that i 've owned the car... I finally set the floats as good as i could. The front is at 12mm and the rear at13mm I also threw the floats in to see how much the liquid lifts. The two LOW points of the carbs are in the side of the idle jet on the first cylinder and at the same spot on the third, so a set them with this in mind. The engine sits like so... The rear carbuetor is a bit tilted inwards. The manifold isn't the best craftsmanship you will see. I have a basic setting now which means closed butterflies, idle steady and low, by pass closed and the mixture screws at 2.5 turns from fully closed. My problem is that the mixtures are non responsive... 2.5 turns or 5 turns is the same. If fully seat them on all 4 cylinder its the same. And the engine doesn't shut off also. I tried some idle jets 55 drilled. It must be now 60-61. The same non responsive mixture. May be unrelated but when coasting at this state of course i have a bit of backfire from the exhaust and on downhills when i brake the engine shuts off. This may be related to the floats that why i am stating it. The manifold is inspected with new flanges so i don't really expect to have a vacuum leak. The carbs can be synchronised with no problem with a tool such as carbtune. I also run a mechanical fuel pump which give a steady 2 psi pressure. The compression of the engine per cylinder with a cold engine was 215, 225, 225, 225 from 1st to 4th. I have also rebuilt them and there is the biggest mistake i made. I bought for half the money the budget rebuilt kit which has needle valves for the trash. So i put back the dellotro oem valves and seats and they seal perfectly as it was tested along with the floats. Generally despite all these fact the engine runs very nice with good progression since i set the floats as it is. The specs of the engine are : toyota 7K 1781 cc Dellorto 40F from alfa romeo Butterflies 7481.3 Venturi 32 Aux venturi 7848.3 Main jet 145 Emulsion tubes 7772.8 Air 210 Pump jet 33 Idle jet 50 Float 7298.1 gr10 Needle valve 150 Stock alfa specs apart from the idle jet which was originally 55... Please help before i sell it Thank you. Link to comment Share on other sites More sharing options...
PeteClan Posted January 30, 2015 Share Posted January 30, 2015 Have you used the section on here in carburetors on how to set Dellorto Float and Fuel Levels. Having always used Webers I used it when I had to set up some Dellorto's I was going to use. Very helpful and I've had no problems. A quick glance at the guide shows that you fuel pressure is too low. Should be 3psi if you are using metal valves and 5psi for Viton ones. Pete Richards Link to comment Share on other sites More sharing options...
ChrisV Posted January 30, 2015 Author Share Posted January 30, 2015 Thanks for your reply Pete ! I followed the guide yes. The manifold sits at a very strange position. There is a big angle with the engine and also there is an angle between the engine and the ground as i showed you on my previous post. I use the metal tipped valves. Could the fuel pressure be my real problem here ?? I have read that the pressure should be 3 psi. I know that carburettors need low pressure so i thought that 2 would be ok. Link to comment Share on other sites More sharing options...
PeteClan Posted January 31, 2015 Share Posted January 31, 2015 You should definately raise it to 3 psi although I think you will need to go to an electric pump and a regulater to achieve it. 2 psi is too low for twin Dellorto's. Did you set the fuel height after the float levels as the guide? Pete Richards Link to comment Share on other sites More sharing options...
ChrisV Posted February 1, 2015 Author Share Posted February 1, 2015 You should definately raise it to 3 psi although I think you will need to go to an electric pump and a regulater to achieve it. 2 psi is too low for twin Dellorto's. Did you set the fuel height after the float levels as the guide? Pete Richards Hello Pete. It seems to me that pressure is not the issue... dellorto.co.uk sells an electric fuel pump that is ideal for weber and dellorto that puts out 2,1 psi fuel pressure and you install it without a regulator. I will recheck the floats as i think it might need more gasoline in the bowl because i measured with the floats in mind... The guide indicates a level without the floats so my levels are lower. I will check this issue and come back with the results. Thanks Link to comment Share on other sites More sharing options...
PeteClan Posted February 1, 2015 Share Posted February 1, 2015 I don't normally disagree on this forum but I have confirm that in my opinion, and based on personal experience, 2.1psi is inadequate for either Weber's or Delorto's. Pete Richards Link to comment Share on other sites More sharing options...
ChrisV Posted February 1, 2015 Author Share Posted February 1, 2015 You may be right ! I have sent an email to eurocarb for this matter, as a technical question. We will see what they will answer on the matter... Link to comment Share on other sites More sharing options...
Triumph-V8 Posted February 3, 2015 Share Posted February 3, 2015 Chris that is no question to far away specialists. The main topic is that there something severly wrong and that is not mentioned in your technical description yet. The mixture screws must bring the engine to stumble when closed and minimum let idle drop when too far out. Whatever the problem is, it will prevent you from finding a proper setup. First the basics must fit, that is same flow through all manifolds, proper idle at all mixture screws and all should than be in a similar position and fuel level must be correct. Link to comment Share on other sites More sharing options...
ChrisV Posted February 3, 2015 Author Share Posted February 3, 2015 Chris that is no question to far away specialists. The main topic is that there something severly wrong and that is not mentioned in your technical description yet. The mixture screws must bring the engine to stumble when closed and minimum let idle drop when too far out. Whatever the problem is, it will prevent you from finding a proper setup. First the basics must fit, that is same flow through all manifolds, proper idle at all mixture screws and all should than be in a similar position and fuel level must be correct. The manifold is tampered with.. because i saw recently an untampered manifold from the same manufacturer... Someone has done some kind of porting it... that is a fact... The ''ports'' of the manifold are enlarged... Link to comment Share on other sites More sharing options...
ChrisV Posted February 3, 2015 Author Share Posted February 3, 2015 My float height levels are now correct i believe. I measured in the middle of the jet stack on the low side (because of the angle of the manifold) Link to comment Share on other sites More sharing options...
Triumph-V8 Posted February 3, 2015 Share Posted February 3, 2015 The manifold is tampered with.. because i saw recently an untampered manifold from the same manufacturer... Someone has done some kind of porting it... that is a fact... The ''ports'' of the manifold are enlarged... To be understood: With "flow" I wanted to say that the sync of the carbs should be perfect. Still the reason why the carbs do not respond that good on the mixture screws must be found next. 1/4 of a turn should be the max that can be turned until the engine responds. Are there air bypasses that are open and could be locked for testing? Link to comment Share on other sites More sharing options...
ChrisV Posted February 7, 2015 Author Share Posted February 7, 2015 Let me give some more information that i have in mind. First of all the floats. I set them as close as to 2,7mm but the fuel level maybe is 1mm or 2mm lower. Is 1mm important or the setting sould be ok ? Secondly the thing i encountered was that with the ''around 60-61'' idle jets the engine didn't change it's working until five turns from fully shut. When i reached five turns the rpm increased. With the 50 idle jets i cannot seem to understand any difference by ear. This could mean that if there is no vacuum leak the correct idle jet for the engine is somewhere between 50 and 60... A 55 maybe ? I don't know. As far as tuning generally i am doing these exact things 1. Bacic setup. Butterflies closed, by pass closed, mixtures 2,5 or 3 turns from fully shut. 2. Turn the engine on and idle as low and steady as possible 3. mixture screws to set up the mixtures And Finally 4. syncing the carbs with a carbtune type tool As far as syncing is concerned as i said i am changing the vacuum. The 1st and 2nd cylinder are close, but i have extreme vacuum to the 3rd cylinder where the servo brake is on the manifold. I am doing it as so : First i find the lowest column in every pair and i align them with the balance screw. Then via the by pass i lower the stronger vacuum (highest column) per pair. One by pass is open in every pair, two in total. This is the whole procedure, maybe this info can be helpful also... maybe there is a mistake somewhere in my doings.. Thanks Link to comment Share on other sites More sharing options...
ChrisV Posted February 7, 2015 Author Share Posted February 7, 2015 Two more details. without any change on the floats. With the big idle jets when breaking and finally stop the engine dies. With the 50 idle jets again when braking and stop it picks up revs In both cases after i get into the garage which is a steep downhill the engine dies and then is very very difficult to turn it on again. Link to comment Share on other sites More sharing options...
ChrisV Posted February 7, 2015 Author Share Posted February 7, 2015 Floats... When i opened the tops i put the calliper at 2,7cm according to the guide and the tip is just touching the fuel. 4-5 minutes after exposing the fuel the measurement went from 2,7 to 3 - 3,1 cm This is what it looks like.. the pictures are after the 4-5 minutes.. I have also the impression that venturis are leaking a bit... I saw it on cylinder no2 one or two drops but i cant tell as generally the auxiliary venturi is always moist. Link to comment Share on other sites More sharing options...
ChrisV Posted February 7, 2015 Author Share Posted February 7, 2015 Oh and this is where i put the calliper.. 3mm away from the jet stack and in the middle Link to comment Share on other sites More sharing options...
Triumph-V8 Posted February 7, 2015 Share Posted February 7, 2015 Hi Chris, I can not fully follow what you are writing due to language problems. What I could detect: You remove the whole top of carb and measure the fuel level? That would be not the correct way. I am not a Dellorto specialist, I had them on my Lotus but swaped them quickly to Weber due to spare part problems. As they work after the same the principles they are similar but the specific data may be different. 27mm fuel level seems to be okay but it is measured after removing the main jet stack. Just drive, stop, switch off and remove the little cap in the middle to get acces to the main jet stack. Into that hole you do the measurement until the fuel level is touched. Look into the hole with a lamp to see the change in reflection when level is touched. The idle jets also have an air jet. At Weber they may be named like 50F8 or 50F9. Although the fuel jet is 50 and both are the same they differ significantly due to the air jet size that is described after the "F". The Dellorto jets are described with a longer number. So do not mix the jets if they have different air jet sizes. The best point of idle setup is when the idle is quickest. As you told it is at 60jet with 5 turns. That is not okay. Try to fiddle that out next. The max should be achieved at 1.5 to 2.5 rpm As you get that too late you do not come into that region that mixture gets too rich at all. Idle fuel jet must be bigger or idle air jet must be smaller. What is curious is that 60 already a pretty big size, so the indication of an air leak becomes more likely. The problem with the sync is something that I do not understand. Sounds all a bit strange and maybe is a hint again that there is somewhere a blown gasket with air passing into the manifold or a similar problem. I do not do the setup by manifold pressure but measure the airflow by pressing an instrument at the filter side of the carb. The engine stall when driving into garage may result from the wrong fuel level. If you have 27mm with fuel bowl removed the level seems to be too high compared to advertised way. The carb simply swaps the fuel into the manifold. Should be better when fuel level is set up. Good Luck! Link to comment Share on other sites More sharing options...
ChrisV Posted February 8, 2015 Author Share Posted February 8, 2015 First of all, thanks for the answer. One thing i can say is that for the float setup i am following the guide that is the first topic and sticky in this section. http://sideways-technologies.co.uk/forums/index.php/topic/1048-setting-dhla-dellorto-dellorto-float-fuel-level/ Is this what you meant by air jet ? The holder ? This is the complete assembly of the idle jet parts in a dhla The one thing i should do if what you say is true is to put the original 55 idle jet back in place. This is the oem part of these carbs. [ If you measure this assembly it is exactly 2,7 cm which in my understanding means that if the carburettor is flat with 0 angle from the manifold the fuel level should touch the orifice of the idle jet. So i have always measured with this in mind. If you check the pictures i posted you will understand that the angle of my manifold orders me to have a high fuel level in order to achieve the 2,7cm so that fuel goes as far up as the idle jet. If i measure from the main jet side i have to lower the fuel level a lot. so much that the car doesn't have fuel to run. Because i mislead myself and did measure and set as such also. I could have damaged the engine. ] I don't know if this assumption is incorrect. I will try your way with the top on and see what happens. I have always had a thought in the back of my head that there might be a problem with the floats themselves, but i tested them in a bowl and they didn't sink but i don't know what might be happening under pressure when driving... The other thing is that i cannot measure the airflow on cylinder 3 and 4 due to a ''crowded'' engine bay. I cannot fit an air flow meter there. Only on cylinder 1 and 2 that why i don't use one. Also i took out the manifold recently, it is now plane, i installed it with the oem gasket and sealant. I cannot be 100% sure there is no air leak, but i believe there is not any. Thanks again. Link to comment Share on other sites More sharing options...
Triumph-V8 Posted February 8, 2015 Share Posted February 8, 2015 Hi Chris, the idle system of Dellorto is different. It seems that the airjet is in the holder what is a big advantage. You can keep that size and only vary the fuel jet. I expect the air jet by the four jets beside the word "holder" in the picture. Reading that article I found it very detailed and precise and so I think he knows what he is doing although I would measure with floats in place but only have the data for that way from Webers. If you lift the whole top the level drops compared to level when driving because you lift the float out of the fuel what had displaced some fuel. That has to be taken into account when the proper height is advertised. Link to comment Share on other sites More sharing options...
ChrisV Posted February 8, 2015 Author Share Posted February 8, 2015 Hi Chris, the idle system of Dellorto is different. It seems that the airjet is in the holder what is a big advantage. You can keep that size and only vary the fuel jet. I expect the air jet by the four jets beside the word "holder" in the picture. Reading that article I found it very detailed and precise and so I think he knows what he is doing although I would measure with floats in place but only have the data for that way from Webers. If you lift the whole top the level drops compared to level when driving because you lift the float out of the fuel what had displaced some fuel. That has to be taken into account when the proper height is advertised. That was my initial thought... 2,7cm fuel height with the floats in place... but the guide says different. If you see the pics the 2,7 height is right below the holes on the main jet stack that are located on the idle jet side. This may be the point of the fuel level. To be right below the holes. I found a guy here in my country that has a gas analyzer and i am going to pay him a visit to discuss the matter because i have heard that he is a true expert in carburettors. I will post an update as soon as i visit him Thanks once more. Link to comment Share on other sites More sharing options...
NeilR Posted February 13, 2015 Share Posted February 13, 2015 Personally I would not worry about the tilt of the engine. I cannot imagine that would have much effect. Link to comment Share on other sites More sharing options...
Pablo Posted February 17, 2015 Share Posted February 17, 2015 Hi Chris, i can tell you that a 60 Idle Jet is not out of the range, because this are Emission Carbs and have a 2,2mm Air bleed hole. Miixture screws with 5 turns out is also O.K. If you use the right Idle Jet holder, without holes at the bottom ( only 4 holes at the Top) But what i can see is a big tilt of the Engine, what i see the Level in the Chamber is aprox 4 mm different in height from left to the right side ? Regards Pablo Link to comment Share on other sites More sharing options...
ChrisV Posted February 19, 2015 Author Share Posted February 19, 2015 Hello Pablo, sorry for the late response. The thing is that at 5 turns is the first time that the engine picks up revs... So the setup is incomplete at that stage. I should go richer... I believe that this is a very rich state. This might indicate a vacuum leak The difference is surely 4 mm and because of that i measured at the center of the jet stack. Always according to the guide in this forum. The engine is tilted as you said but the carburettors also form a big angle with the engine ! Link to comment Share on other sites More sharing options...
ChrisV Posted February 21, 2015 Author Share Posted February 21, 2015 The ''trip'' to the gas analyser is on hold for the moment because of a problem with the clutch pedal. I ll get back to it once i finish with that. Then i ll post an update. Link to comment Share on other sites More sharing options...
ChrisV Posted May 22, 2015 Author Share Posted May 22, 2015 Let's update the topic a bit... Oh boy... The first thing i found and solved (which is my fault because i rebuilt the carbs as i said) was that both cold start chokes were stuck open... I don't know why i didn't think about that and left them without care... nevertheless a friend threw the idea after encountering the same thing with his DRLA and voila... chokes are both shut - idle never goes up for no reason as it did before.. Secondly, after i saw this, i thought i should take them out of the engine and do a chemical bath.. i cleaned them before with sprays and compressed air but something was bothering me. So i did. I also found out that when you opened the throttle the pump jets of the front carburettor (cylinder 1 and 2) was not spraying instantly as it should.. One of the springs of the pump rod snapped during the disassembly due to corrosion, so i bought o new pair... The pump jets were set to spray instantly and everything was cleaned and tested on the bench. The carbs are on the manifold now with new gaskets and a float setting appropriate to the angle of the manifold (no venturi leaks) at 20mm (17mm was the previous and a lake of gas was formed into the venturi) and the droop set is 26mm which i am considering of taking it to 30mm because the stock reference of dellorto is 15 float set and 25 droop (10mm difference and i have only 6mm) And i also put genuine dellorto needle valves and new floats of 10 grams The response of the engine is instant but it bogs on low rpm if you quickly depress the pedal... also the mixture screws continue to be unresponsive... I shut the by-pass screws, i close the butterflies and lower the idle as low as possible. 2.5 turns from fully closed, or 6 turns is the same thing for the engine... the idle does not change whatsoever Any thoughts or ideas, or anything i could try is always welcome... Link to comment Share on other sites More sharing options...
ChrisV Posted May 24, 2015 Author Share Posted May 24, 2015 The lean spot and unresponsive mixture was due to a small idle jet. 50 was small for the engine... I tried a set of 60's and the mixture screws are for the first time responsive... Now we're talking... the gas analyser will now provide the tuning, or fine tuning necessary for the engine to work as it should I may also need to tight a bit the pump rod's nut, because on 3rd and 4th gear it leans on quick depressing of the pedal, but i will see to that after i complete the tuning process Link to comment Share on other sites More sharing options...
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