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Thread: Trumpets?

  1. #1
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    Trumpets?

    right im not actually thinking about powering my car by wind instrument!

    But as some may know I have an Alfa boxer engine with twin Dellorto carbs, my old K&N filters have become bent and buckled over the years of storage.

    Im just after some advice on what people think the best options are do I get another set of these or do I go for individual trumpets and socks?

    my main question is suppose is what is the purpose and differences in different lengths?

    Keith

  2. #2
    The purpose is;
    A. Any 'blow back' out of the carb's venturi is sucked back in before it can disperse so none is wasted, I use 40mm ones under a 4" filter.
    B, The air flow into the venturi is smoothed out and enters at a slightly enhanced speed (hence "velocity stacks", improving consumption and power.
    A decent filter over the top is better than ones on the stack and less restrictive. The ones I use on my 44's are common on many set ups.

    There are various formula and charts in the DellOrto tuning book, well worth buying a copy, also deals with tuning VW engines a bit but that is a HUGE subject.
    MkII breather.jpg DelOrto.jpg

    Dunno if I said this before but one can get longer air screws which make tuning in confined spaces a doodle.
    air screw.jpg

    Information DellOrto tuning book, Ebay
    Last edited by Peter; 13-02-2016 at 03:35 PM.



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  3. #3
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    thanks for the info

  4. #4
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    K&Ns are pretty good, but as Peter says, they lose a very slight edge compared to velocity stacks. However, for road use I doubt you would notice the difference, and the main thing with Alfa engines is to ensure no dirt or crud gets into the carbs. Actually that applies to any engine, but my point is, velocity stacks look great, but unless you are rebuilding the engine on a regular basis they need to be covered by big foam air filters anyway (like ITG), so you could do a lot worse than just clean out your K&Ns!

    Lauren
    only Pythagoras can save me now!

  5. #5
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    the issue with my K&N's is the filters are crushed so thinking about stacks as they do look better but cant see how they mount without an adapter plate

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    Having read through lots of threads ref Alfa engines, its always good to read the ones that have those engines already in. Giles Nova, Albanova, Islandmans are just three and they all have write ups about the Alfa engine.

    From reading Giles' I then found an entry about stacks. Look under the heading Engines on the forum. On page 2 of the listings dated 23/4/2012 is the heading " Carb Velocity Stacks". Worth a read.

    The advanced search is very helpful.

    The Alfa forum is another good area for guidance and advice

    And of course Spacenut !!!!

    Buffy

  7. #7
    Quote Originally Posted by kdnova View Post
    the issue with my K&N's is the filters are crushed so thinking about stacks as they do look better but cant see how they mount without an adapter plate
    They have a flange which uses the 4 screws in the top plate,
    trumpet bolts.jpg
    One can get stacks with a one piece cover plate but not really needed if using a filter base plate.
    DelOrto.jpgstacks with palte.jpg

    If you want to fit stacks without a filter, (unadvisedly) then a simple alloy cover plate could be made to go under the stacks and cover the carb.
    Last edited by Peter; 14-02-2016 at 05:14 PM.



    The opinions expressed in my posts may not be made in a sound mind and should be taken in the spirit intended, Jack Daniels is fine.
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  8. #8
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    At least with the 1.7 Alfa the carbs will be 40mm. The 1.5 litre engines like mine had specially made 36mm venturis for which velocity stacks are not available.

    Lauren
    only Pythagoras can save me now!

  9. #9
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    yes they are 40mm carbs

    And thanks for the info I think I need to make some form of adapter as my filter bases all ready are thin tin and only have 2 mounting screws

    I have measured the distance from top of carb to under engine cover and I have 100 mm. My thoughts is some 70mm (ish depending what is available) fitted with ITG socks or they do a cover for 2 trumpets in one

    keith

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