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Thread: Over-boring a Weber 32/36 dgav

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    Rolleyes Over-boring a Weber 32/36 dgav

    Hi guys. Can anyone please show me the proper way to bore out a Weber 32/36 dgav carb from 26/27 to 27/28? I read an article in Hot Rod Magazine (USA) quite a few decades ago that off-roaders from California tweak their Webers that they use in their air cooled VW engines. Cheers!!

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    Re: Over-boring a Weber 32/36 dgav

    theres loads of ways to do it, if you carefull you can do it by hand with a die grinder and drum roll. its better done in a milling machine or lathe though, as you ideally need to maintain the original cross sectional shape

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    Re: Over-boring a Weber 32/36 dgav

    Overbore 1mm in first step, 2mm (max) for second and they will flow a lot more power (I'm not talking about air, it's just not working this way). With this mod it should flow enough "air" (power) for any Pinto engine. The rest of the engine (single carb manifold setup) will not be much better so extra air will not make extra power.

    You can "round" it all up with Dremel at the entry, same on the other side. Best way to do the part between choke and throttle plate is using a lathe but centering is difficult because it's all "cast" on top, it is not correct center. This way you can make the exit of the choke correct at the right angle but don't worry too much, it will work as it is too. I regular build this kind of carbs (also 38 DGAS for V8 engines where I use a larger turned out choke). Only little extra makes already good results. Going too large and the carb will be a pig to tune on the road.
    Last edited by onyd; 12-01-2020 at 15:17.

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    Re: Over-boring a Weber 32/36 dgav

    Quote Originally Posted by onyd View Post

    You can "round" it all up with Dremel at the entry, same on the other side. Best way to do the part between choke and throttle plate is using a lathe but centering is difficult because it's all "cast" on top, it is not correct center. This way you can make the exit of the choke correct at the right angle but don't worry too much, it will work as it is too.
    just like parallel boring dcoe chokes, technically bad, but most people do it that way and they still work!

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    Re: Over-boring a Weber 32/36 dgav

    Correct, as long as you don't bore 30mm to 36mm it is working. And even if you do it, with some funny jetting it will still work.

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    Re: Over-boring a Weber 32/36 dgav

    Sir Onyd, could you show me, precisely by drawing, how to bore out the Weber DGAV carb properly? I am new at this and any wrong instruction I give the machine shop will just destroy the carburettor.

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    Re: Over-boring a Weber 32/36 dgav

    Sir Graham, Is it correct to say that I can only bore out 1 mm on each of the primary & secondary barrels? If I bore them both 2 mm, would my carb still be tuneable? What is the proper size Auxiliary venturi to use in each barrel after over-boring them 1 mm? Thanks.

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    Re: Over-boring a Weber 32/36 dgav

    For not having any tuning problems, just bore first step max 1mm en second max 2. Even 1mm is enough in most cases. If flow a lot more power. Please note, it will only help you further if the engine can use the extra air, otherwise it is a waste of time.

    For a standard engine, 1mm in second stap will be all what is needed, leave the first step standard.

    Just drill it out straight 1mm. Milling machine is most easy to center. Use a Dremel and some abrasive paper to round off the corners and it will work just perfect.

    The most important part to keep your carb tunable is the camshaft. If you add to much valve lift at TDC or too much duration, the carb will be very difficult to be tuned.

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