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kdnova
12-02-2016, 10:11 PM
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

Peter
13-02-2016, 03:00 PM
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.
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Dunno if I said this before but one can get longer air screws which make tuning in confined spaces a doodle.
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Information DellOrto tuning book, Ebay

kdnova
13-02-2016, 04:32 PM
thanks for the info

Spacenut
13-02-2016, 09:30 PM
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

kdnova
13-02-2016, 09:50 PM
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

Buffy
13-02-2016, 11:15 PM
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

Peter
14-02-2016, 05:07 PM
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,
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One can get stacks with a one piece cover plate but not really needed if using a filter base plate.
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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.

Spacenut
14-02-2016, 08:08 PM
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

kdnova
14-02-2016, 08:26 PM
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