David Vizard always used to maintain that the Dellorto DHLA carburettor produces finer fuel atomisation that the Weber and that it was better suited to open combustion chamber configurations lacking in effective squish area.
Question that no one seems to answer - Dellorto DHLA idle and progression. The idle jet on it's own is simple to understand but the idle air bleeds ? Setting idle is all about the progression up to the main circuit taking over, bigger idle jet is richer and smaller is leaner. But how does the idle air bleed work, why are there different air bleeds ? They look like smaller emulsion tubes so do they work similar to the main jet emulsion tubes ? Does a rich idle air bleed get progressively richer in the same manner or a lean idle air bleed get progressively leaner until the main circuit takes over ? Other articles seem to comment on the idle jet and idle air bleed as separate items but offer no correlation as to how they work together or what difference happens with different combinations ? If you could answer that, you will be my hero. Thanks in advance.
Awesome question! My theory is that they did it this way to be able to “tune out” the situation especially in racy engines where the idle has to be too fat due to low vaccum because if not the progression stage does not work. I had this problem with Weber 48 DCO SP on a Jaguar E type lightweight. The idle (tick over) was way too fat but you could not lean it out beside of the progression. My guess is that with dellortos I would have been able to tune that out. Hope this helps
@@carburist Awesome answer almost. You clearly understand exactly what I'm trying to understand because of your E type problem. I'm working with Dellortos and believe in your theory too, but I still don't understand the relationship of idle jet to idle air holder in order that I perform the correct process to get to the correct answer ? I have 50 idle jets with 7850.1 air holders, it idles a fraction lean but falls flat lean with gentle opening of the throttle. If I change to 7850.2 air holders (catalogue says they're much richer) with the same 50 idle jets, am I heading in the right direction ?
Do the single barrel Dellorto carbs seen on motorcycles (1 per cylinder, like on a Harley XR) have butterfly throttles like these, or do they have a slide action?
I'm tuning a 74 afla romeo 2.0 GTV with Dellorto DHLA 40E. Experiencing popping and think that these are lean pops so should go up a jet size. Your thoughts?
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David Vizard always used to maintain that the Dellorto DHLA carburettor produces finer fuel atomisation that the Weber and that it was better suited to open combustion chamber configurations lacking in effective squish area.
Yes!
Question that no one seems to answer - Dellorto DHLA idle and progression. The idle jet on it's own is simple to understand but the idle air bleeds ? Setting idle is all about the progression up to the main circuit taking over, bigger idle jet is richer and smaller is leaner. But how does the idle air bleed work, why are there different air bleeds ? They look like smaller emulsion tubes so do they work similar to the main jet emulsion tubes ? Does a rich idle air bleed get progressively richer in the same manner or a lean idle air bleed get progressively leaner until the main circuit takes over ? Other articles seem to comment on the idle jet and idle air bleed as separate items but offer no correlation as to how they work together or what difference happens with different combinations ? If you could answer that, you will be my hero. Thanks in advance.
Awesome question! My theory is that they did it this way to be able to “tune out” the situation especially in racy engines where the idle has to be too fat due to low vaccum because if not the progression stage does not work. I had this problem with Weber 48 DCO SP on a Jaguar E type lightweight. The idle (tick over) was way too fat but you could not lean it out beside of the progression. My guess is that with dellortos I would have been able to tune that out. Hope this helps
@@carburist Awesome answer almost. You clearly understand exactly what I'm trying to understand because of your E type problem. I'm working with Dellortos and believe in your theory too, but I still don't understand the relationship of idle jet to idle air holder in order that I perform the correct process to get to the correct answer ? I have 50 idle jets with 7850.1 air holders, it idles a fraction lean but falls flat lean with gentle opening of the throttle. If I change to 7850.2 air holders (catalogue says they're much richer) with the same 50 idle jets, am I heading in the right direction ?
Immensely helpful. Great work.
You’re welcome
Thank you for this video!
Do the single barrel Dellorto carbs seen on motorcycles (1 per cylinder, like on a Harley XR) have butterfly throttles like these, or do they have a slide action?
I think they are sliders!
Thank you
I'm tuning a 74 afla romeo 2.0 GTV with Dellorto DHLA 40E. Experiencing popping and think that these are lean pops so should go up a jet size. Your thoughts?
Yeah, good to try with that
We also have a Alfetta gtv 2.0 of 76. We have the DHLA40G. We think They are broken. We bought a DHLA40E. What is the difference?