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Thread: 42mm chokes in 45mm dcoe.

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    42mm chokes in 45mm dcoe.

    hi all

    has anyone tryed using modiftyed 42mm chokes in twin 45mm dcoe weber carbys

    for a pinto 2 litre any feed back cheers mario,

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    Re: 42mm chokes in 45mm dcoe.

    pointless exercise if you ask me, the carb wont work properly because there wont be enough size difference between the choke and body for the venturi to actually work, you will meed massive main jets, and in all probability wont gain any air flow

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    Re: 42mm chokes in 45mm dcoe.

    What mods have you done to the carbs so far. ADV spindle etc? There is more flow to be had before you need to go up in choke size.

    Shaun.

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    Re: 42mm chokes in 45mm dcoe.

    Hi shaun were can you get the adv spindles from i cant find them anywere cheers mario.

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    Re: 42mm chokes in 45mm dcoe.

    Look down the throat of the carb. What are the obstructions for flow. How can you modify them to improve. Or, look at other carbs, eg holley, and see what they are doing for their ADV and modify to suit the dcoe.

    Otherwise, think outside the box, this is what can be achieved.

    https://www.youtube.com/watch?v=kXRzSY4Xzic

    Shaun

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    42mm chokes in 45mm dcoe.

    Don't like the sound of that 😐😣😄


    Sent from my iPhone using Tapatalk

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    Re: 42mm chokes in 45mm dcoe.

    The video is not the best example as I think he removes them completely....

    This is what you want.

    Works better than standard and loads more flow.
    Attached Thumbnails Attached Thumbnails dcoe2.png‎  

    Last edited by escortinadriver; 04-02-2018 at 22:01.

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    Re: 42mm chokes in 45mm dcoe.

    i was referring to the name "annular discharge"

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    Re: 42mm chokes in 45mm dcoe.

    on webers you can remove one leg from the aux vent (dellortos only have one in the first place)

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    Re: 42mm chokes in 45mm dcoe.

    What gain will i get by removing one leg in the aux ventri im running 40mm chokes will it give the sqme affected like using a 41 or 42mm choke cheers mario.

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    Re: 42mm chokes in 45mm dcoe.

    dellortos only have one leg, so presumably dellorto felt there was a benefit. i cannot believe that 40mm chokes in 45mm carbs will be reducing airflow through the carb, but you might find a small airflow gain by removing a leg.

    if you ask me all a 42mm choke in your carbs will do is loose all the bottom end and require massive main jets. you would be better of with 48mm carbs and 40mm chokes in the first place

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    Re: 42mm chokes in 45mm dcoe.

    Cheers graham i only want more top end power from 4000 to 7500 rpm engine is for drag racing i know high hp pinto use 42mm chokes.

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    Re: 42mm chokes in 45mm dcoe.

    but not normally in 45mm carbs!

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    Re: 42mm chokes in 45mm dcoe.

    Just been reading your private message. Just as Graham says, you will end up with very big mains and probably no torque or any real gain. If it's a 2 Ltr Pinto, I can hardly believe it can outperform a 45 with 38 mm chokes but I don't have any idea how far they can go in drag race (how high in rev because this will more than anything else put his number on the size of a carb). I have no idea how good there heads are and how high they can still make volume in the engines. If you really need 42 chokes, you are probably at the point you can use 48 DCO with succes.

    In the Youtube video I can see "Patent Pending". Sorry, this technology already exist for many many years, together with a lot of other setups. Sometimes they work, sometimes not. Usual they are not as "universal" compared to the standard (Weber in this case) setups.
    Last edited by Dyno; 10-02-2018 at 22:08.

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    Re: 42mm chokes in 45mm dcoe.

    A 36mm custom full length 'ADV' like the one in the picture will flow as much air as a 42mm choke. A 38mm will flow as much as a 46mm choke.

    Shaun.

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    Re: 42mm chokes in 45mm dcoe.

    hmm, i find that difficult to believe, total air flow is a combination choke, body size and throttle spindle/butterfly

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    Re: 42mm chokes in 45mm dcoe.

    I do believe in flow testing etc.. but I don't believe in trying to find the biggest CFM when it comes to carb selecting. There is more involved when you start selecting a carburetor + very important, CFM only does not take in account air speed, pulse tuning (very important when it comes to cylinder filling).

    I'm not an expert in mats, all I can see are the numbers my dyno produce (very often I also don't have a logic explanation). Let's keep it simple, if CFM is the most important, why is an engine not producing more power every time you step up your carb size or ITB size (so we don't have to start the discussion carbs no longer suck fuel when they get bigger). And believe me the answer is not, because the size was big enough it is no longer producing more power. No the size get's bigger and the power start to drop (usual first at the bottom of the power graph but later all over). That's real live.

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    Re: 42mm chokes in 45mm dcoe.

    Quote Originally Posted by Graham View Post
    hmm, i find that difficult to believe, total air flow is a combination choke, body size and throttle spindle/butterfly
    Sorry Graham, Should have been a bit more specific, was referring to info on a set of 50's, from here;

    we performed the very thing you discuss with a pair of 50DCO side-draft Weber's we run on a full-race, roller-cammed 2.0L Ford 4-cylinder. We removed the booster and standard venturi(choke), then manufactured what I call an ADV (annular-discharge-venturi) that runs the full length of the carb throat. The formula's that we used? For the holes in the discharge ring, we measured/used the area of the standard booster discharge 'hole'. We then found/calculated that [9] annular discharge holes, .062" in diameter, would equal, plus 3-4%, the area of the standard discharge hole on the 50DCO booster. That's what we used. The diameter of the venturi? For good 'snap' off paved-oval corners, we decided to flow the carbs with standard venturi's near 80% of the throttle blade base diameter. We had flowed the carbs with standard 38/40/42/44/46 mm diameter chokes and decided we needed an ADV that flowed nearly the same as 40mm & 42mm chokes(~80% of 50mm). Subsequent to milling a lot of aluminum, cut-and-try, we found that a 36mm diameter ADV flowed dry air right at a standard 42mm choke/booster. So....... for short-track paved ovals, we manufactured 36mm ADV's. They worked well beyond our wildest expectations! And the most amazing thing? The 'main well' signal at the ADV was 33% better than the same signal with a 42mm choke/booster. Which led to a jetting situation. Even though the 36ADV flowed dry air as well as a standard 42choke/booster, if I jetted the carb for the 42, it was pig rich. So I wound up jetting about the same as a standard 36-38 choke. I contribute the jetting situation to mixture QUALITY(annular discharge) and signal strength. Then we got wild and crazy! One of our tracks was the very high speed Mesa Marin (now bulldozed) 1/2-mile @ Bakersfield, CA. Nearly WOT with a 1000rpm operating band around the track. We built 38 ADV's specifically for that track. The 38 ADV flowed dry air about the same as a standard 46 choke/booster. And the main well signal was 37% better with the ADV. Over [3] seasons and [6] races @ Mesa Marin, we were undefeated with the ADV's. Bottom line? If our Weber/ADV experience is any indicator, and we had the machining capability/time, none of our carbs would have a booster...... even the Holley's!

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    Re: 42mm chokes in 45mm dcoe.

    This whole story does illustrate the setup was working for there application. Believe me, it can be opposite as well.

    33% better signal. Where? It has no sense to have a bigger signal if you just want to get rid of fuel at this point. Tuned engine react totally different to boost signal as standard engine. I just had an engine I could not get rid of the over fueling at low RPM (due to back spit in the carb, and don't know yet why this is so bad compared to other engine of the same spec). I which I would had LESS boost signal at low RPM, or have more at top. So the point is, where do you want more signal. Some booster can place the point of highest signal (deepest vac.) in an other point of the air volume (RPM) range. If this suits your setup better, you gain. Little to do with overal CFM

    For all out racing I've seen none standard setup and they did work. But not always. Just like a single tube full of holes instead of aux. choke. Usual only in the power band they have to work.

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