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Thread: Twin dellortos struggling past 3500rpm

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    Twin dellortos struggling past 3500rpm

    First up is engine spec.1720cc244 cam accuspark blue coil ballast and vacuum distributor accuspark plugstwin 40 dellortoschoke 32mains 140emulsion 777.5air corrector 110thats all info I have at moment.engine starts no problem, pulls nicely and and feels good up to and sitting at 3000rpm.start pulling past it and I get hesitation and stuttering, having to back off to about 2000rpm to let it settle and then it will sit at 3000rpm again no problem. Try pulling past it and it will repeat.facet pump with king filter pressure was at 3psi. Increased to 4 psi and no change.any opinions on what it could be? Fuel starvation?had a read about needle valves but don’t know what size should be right.i will just add I did pull over on one occasion because fuel smell and fuel was dripping out trumpets3 and 4. Turned everything off for a while and that hasn’t happened since. Maybe stuck needle valve?thank you

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    Bodger

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    Re: Twin dellortos struggling past 3500rpm

    that can be different things happening. Hard to say whats going on. But first did you check the carbs completely? float settings ok? Accelerator pump jets?
    Fuel Discharge nozzle ect. Are the carbs in 100%working order? Go and check your carbs on working order first. Even overhaul them when they are used ones.
    Cant tell you bout the aircorrection jet, cause i got Webers now. But 140# mains shouldnt be the problem, i think it is acceleration side of carb. But beats me what happend
    with fuel dropping out carbs. Could be Float bowl , dumping fuel over and that causes troubles too. Just hard to tell from this information you give. Start by checking carburettors completely
    Are they OK or not.

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    Re: Twin dellortos struggling past 3500rpm

    110 air corrector seems very small given a 140 main, which actually seems a bit big given the spec

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    Bodger

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    Re: Twin dellortos struggling past 3500rpm

    if thats a #110 indeed i would say to small. I had run 145 mains with 170 aircorrection, but that was on my webers on a 1600cc crossflow

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    Re: Twin dellortos struggling past 3500rpm

    i think you mean 7772.5 emulsions?? what series Dellortos are they? if they are C or E or dont have a letter, then they arent the emissions carbs, which is good and your emulsions should be fine. if they are any other letter then they are emissions carbs and you will need the correct emulsion tubes, they're still gonna be a little painful to tune though... think they use emulsions 8 and above, look like swiss cheese. 110 is way too small for air correctors, cant say ive heard of anyone using a air corrector smaller than a main jet, other than when compensating for something, like you have to do with emissions variants. 2500-3000 is about the time it would be switching to the main jet circuit so start there after you have checked nothing is leaking etc.. http://www.s262612653.websitehome.co...s/dellorto.htm for a bit of reading. should get you close with jetting.

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    Re: Twin dellortos struggling past 3500rpm

    I have been having internet issues since posting and my replies haven’t shown.

    I had the carbs set up and balanced by a carb bloke about 6 months ago. Confirmed carbs had been refurbed, listened with his pipe, checked exhaust gases and took mains jets etc out to see what he was working with.
    At the time car had no mot so couldn’t go for a
    Run in it.
    I will try post a picture of card he left me with the sizes on later.

    I’ll have a look at some of the things mentioned in this thread. Maybe be worth trying to find an old school carb bloke who has a rolling road?

    Any recommendations for the midlands?

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    Re: Twin dellortos struggling past 3500rpm

    I have been having internet issues since posting and my replies haven’t shown.

    I had the carbs set up and balanced by a carb bloke about 6 months ago. Confirmed carbs had been refurbed, listened with his pipe, checked exhaust gases and took mains jets etc out to see what he was working with.
    At the time car had no mot so couldn’t go for a
    Run in it.
    I will try post a picture of card he left me with the sizes on later.

    I’ll have a look at some of the things mentioned in this thread. Maybe be worth trying to find an old school carb bloke who has a rolling road?

    Any recommendations for the midlands?

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    Bodger

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    Re: Twin dellortos struggling past 3500rpm

    I can tune them, but Staffordshire is a bit far travel to south of Holland LoL. But seriously, Dell"orto is different with their numbers compared to Weber.
    I have Dell'orto as well, not used ( reconditioned ) yet. Story goes that Dell'orto had better fuel atomization compared to Weber. Anyhow, your air correct
    nozzle is to small like Graham said. To start of go bout quarter the size of your mains above, so 140 main 175 air. E Tubes are a important matter as well for enrichment mixture.
    I only can tell from my Kent 1600 i had, it had a kent cams 234, mild ported head, tubular exhaust from GT nothing fancy "fast road" engine, Just to compare with yours;
    I had Weber dcoe with 32 chokes ( wich was best ), #45F9 idle, #40 pump jets, F16 Etube, #170 air. Cant remember for sure what discharge nozzle i got down there.
    Maybe you can find usefull bits out of this. I know it is different but some may be comparable. But what i saw to many times that people just did not get their
    carburettors in good working order. Crooked floats, floatlevel off, butterflies rod ( how's the english name ? ) twisted. Just to say before any tuning, check if your carbs
    are in good condition.

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    Bodger

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    Re: Twin dellortos struggling past 3500rpm

    I can tune them, but Staffordshire is a bit far travel to south of Holland LoL. But seriously, Dell"orto is different with their numbers compared to Weber.
    I have Dell'orto as well, not used ( reconditioned ) yet. Story goes that Dell'orto had better fuel atomization compared to Weber. Anyhow, your air correct
    nozzle is to small like Graham said. To start of go bout quarter the size of your mains above, so 140 main 175 air. E Tubes are a important matter as well for enrichment mixture.
    I only can tell from my Kent 1600 i had, it had a kent cams 234, mild ported head, tubular exhaust from GT nothing fancy "fast road" engine, Just to compare with yours;
    I had Weber dcoe with 32 chokes ( wich was best ), #45F9 idle, #40 pump jets, F16 Etube, #170 air. Cant remember for sure what discharge nozzle i got down there.
    Maybe you can find usefull bits out of this. I know it is different but some may be comparable. But what i saw to many times that people just did not get their
    carburettors in good working order. Crooked floats, floatlevel off, butterflies rod ( how's the english name ? ) twisted. Just to say before any tuning, check if your carbs
    are in good condition.

  10. #10
    Bodger

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    Re: Twin dellortos struggling past 3500rpm

    and balancing, often a thing people forget to get it right. It needs checked every now and then

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    Re: Twin dellortos struggling past 3500rpm

    Update now I am at last able to get onto this site again. Seemed to be down for almost a few weeks.

    I ordered 175 and 195 air correction, 130 mains and 1.75 needle valves. Took out the 110 airs and looked no different to the 175s. It looked to me like they had been drilled. So I installed the 130 mains and 175 airs with new needle valves and all seems like it working. Couldn’t tell you what single part changed it.
    Just pleased it’s going well now.
    I shall continue to run it in upto 500 miles then get it set up with a rolling road.

    Thank you for the reply’s and help

  12. #12
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    Re: Twin dellortos struggling past 3500rpm

    In your initial post you say you have a vacuum distributor, how have you got the vacuum connected ?. With twin Dellortos or Webers you mustn't connect the pipe to just one manifold runner.

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