Discussion
I'm looking to replace the air filters on my crossflow running twin weber 40's, but am struggling to find anywhere on the web that provides useful info on considerations and why/when you would opt for the different types of filter available. Manuacturer and dealer sites just provide basic spec's and prices. Anyone recommend a good point of reference for some guidance on selection. Thx.
Hi Steve. Sorry can't help with tech spec but just to say that I have twin 40s and have purchased a pair of Eurocarb filters. My choice was driven by physical dimensions and price. As you know, the space is tight between the filter and the inner arch on the front carb. When I purchased the car it was fitted with old speedograph type filters which are still available I think. The Eurocarb filters look to my untrained eye to be surprisingly well made and have a simple oval shape and chrome finish with no logo - which i liked. How flow efficient they are I simply don't know but they will stop sparrows getting sucked into the engine!
Just to add to tomtrouts post, the length of manifold will also influence the choice.
A longer inlet manifold should allow a larger filter to be used, as the carbs are angled slightly more upwards than the short manifold.
We've got a short manifold on ours, and we couldn't use the eurocarb filters (think they were from there), so we're running some webcon gauze covers on the ends of the trumpets.
We've got a longer manifold ready to go on, so we can use some bigger filters, just got to get around to fitting it.
Probably not much help really,
Basic thing with air filters I believe, it just to try and get as much filter area as possible, and a good quality filter.
So anything from K&N, Pipercross, ITG etc should be fine. As above, size will be determined by how much room you've got available.
A longer inlet manifold should allow a larger filter to be used, as the carbs are angled slightly more upwards than the short manifold.
We've got a short manifold on ours, and we couldn't use the eurocarb filters (think they were from there), so we're running some webcon gauze covers on the ends of the trumpets.
We've got a longer manifold ready to go on, so we can use some bigger filters, just got to get around to fitting it.
Probably not much help really,
Basic thing with air filters I believe, it just to try and get as much filter area as possible, and a good quality filter.
So anything from K&N, Pipercross, ITG etc should be fine. As above, size will be determined by how much room you've got available.
Hi Andy. The reason for the question is the options seem to be a traditional type filter - either 1 x double or 2 x singles. The likes of K&N also offer socks that go over ram pipes and mesh filters that go over ram pipes.
Non of the sites I've found state advantages / disadvantages of each nor whether they are only suitable for certain uses (ie race/road).
As you say, room is tight in the Vixen, I'm limited to 70mm between rear carb and the inner wing. Oddly I have more room between front carb and the inner wheel arch.
Non of the sites I've found state advantages / disadvantages of each nor whether they are only suitable for certain uses (ie race/road).
As you say, room is tight in the Vixen, I'm limited to 70mm between rear carb and the inner wing. Oddly I have more room between front carb and the inner wheel arch.
We were told by our rolling road guy not to bother with the socks, as they can sometimes get sucked into the carb. I think he also said he'd seen losses of up to 15bhp with the socks.
I think, if you can get a decent filter on with some ram pipes inside, that would give the best results, as it makes the best of the ram pipes.
With the gauze covers, you kind of lose the very outside of the curve of the ram pipe because of the rubber boot to hold the filter onto the pipe. We did test them on the rolling road, by doing a run with and one without, can't remember how much bhp they lost, should be able to find the bit of paper somewhere.
I think, if you can get a decent filter on with some ram pipes inside, that would give the best results, as it makes the best of the ram pipes.
With the gauze covers, you kind of lose the very outside of the curve of the ram pipe because of the rubber boot to hold the filter onto the pipe. We did test them on the rolling road, by doing a run with and one without, can't remember how much bhp they lost, should be able to find the bit of paper somewhere.
Foam filters are a bonfire waiting to happen. Every time it spits back, and with twin Webers it will, you are dousing the filters with fuel, big sponge. Its even more serious if you get a fuel stand off .
Remember if you get a carburettor fire the best way to put it out if floor the throttle
Remember if you get a carburettor fire the best way to put it out if floor the throttle
Moto said:
Hi Andy. The reason for the question is the options seem to be a traditional type filter - either 1 x double or 2 x singles. The likes of K&N also offer socks that go over ram pipes and mesh filters that go over ram pipes.
Non of the sites I've found state advantages / disadvantages of each nor whether they are only suitable for certain uses (ie race/road).
As you say, room is tight in the Vixen, I'm limited to 70mm between rear carb and the inner wing. Oddly I have more room between front carb and the inner wheel arch.
I don't understand how you are having a difficult time finding something to work with 70mm clearance. Non of the sites I've found state advantages / disadvantages of each nor whether they are only suitable for certain uses (ie race/road).
As you say, room is tight in the Vixen, I'm limited to 70mm between rear carb and the inner wing. Oddly I have more room between front carb and the inner wheel arch.
The re-usable metal mesh covered folded paper type from K&N have a rubberized perimeter, and if memory serves, come in a variety of heights. What trumpets are you using, and are they coordinated with the cam? Have you considered a plenum, with a hose to a cold air high pressure box, with a big filter? If you want it to look period, paint it black crackle.
Another option could be to have a look at what the Pantera folks do. As I recall, there are long, single filter elements available that are utilized with their Weber set-ups, and similar ones on the Autolite I-4 carbs. (A friend of mine had the DUALS on a 351 Cleveland in an early Pantera, and they were gorgeous ... without filters.)
I suppose, if you're working on a car for street and track, you could always remove the filters on race day. Air filtration is always going to be a compromise between cleanliness and restriction.
Best,
B.
Disadvantage of K&N type filters is if there s too small a gap between the end of the trumpet and the outer plate of the filter this can seriously upset the airflow into the carb restricting power and even causing resonance resulting in fuel spit-back. I use Pipercross domed foam filters on my 1600M as they will deform against the chassis rail still leaving a gap over the trumpets, I am going to try an airbox on the Vixen again Pipercross, Burton power have dimensions on their website. Geoff
OK, so spoke to a local chap who races Healey's running weber's. He agreed with you Steve as foam being a bonfire waiting to happen and has seen a few such cases. That's one option ruled out.
Interesting feedback Thomas on the webcon gauze covers on trumpets. These are a variation as the gauze is non-removable therefore there's no rubber to disrupt airflow.
http://www.dellorto.co.uk/merchandise/products_det...
The current filters are k&n type but a cheapo version that were fitted at some point in it's past. The trumpets have also been removed so there is just the hole in the back plate. Presumeably as the depth of these filters is just 40mm, the original trumpets were too long or at best would have been almost touching the front plate, so someone decided to just take them out.
So basically option 1 : buy 4 x trumpets & filter. The obvious choice is to buy 2 x K&N small oval filters which are 63mm deep. This is the deepest I can go within the 70mm space available. With 4 x 39mm slot in trumpets, this would give a 24mm gap. Should be OK.
Option 2, I could buy 4 of the trumpets with fitted gauze. The upside is they work out 20% cheaper than filters and also 'I think' asthetically would be pretty. However maybe a downside of poorer filtration & air flow.
Interesting feedback Thomas on the webcon gauze covers on trumpets. These are a variation as the gauze is non-removable therefore there's no rubber to disrupt airflow.
http://www.dellorto.co.uk/merchandise/products_det...
The current filters are k&n type but a cheapo version that were fitted at some point in it's past. The trumpets have also been removed so there is just the hole in the back plate. Presumeably as the depth of these filters is just 40mm, the original trumpets were too long or at best would have been almost touching the front plate, so someone decided to just take them out.
So basically option 1 : buy 4 x trumpets & filter. The obvious choice is to buy 2 x K&N small oval filters which are 63mm deep. This is the deepest I can go within the 70mm space available. With 4 x 39mm slot in trumpets, this would give a 24mm gap. Should be OK.
Option 2, I could buy 4 of the trumpets with fitted gauze. The upside is they work out 20% cheaper than filters and also 'I think' asthetically would be pretty. However maybe a downside of poorer filtration & air flow.
Webers are not meant to be run with out velocity stacks fitted, as the stacks keep the venturi's from floating in the carb bore. I have fitted short K&Ns with shorty stacks with excellent results. The backing plate of the filter housing will need to be enlarged. Look up Pierce Manifolds and you will find everything you need.
Cheers,
D.
Cheers,
D.
I'm surprised the clearance is tight for your rear carb. Is the bulkhead on the S3 a different shape? The bottom of the filter clears the top of the footwell on mine although not really clear on the photo? You can't really see the clearance to my inner arch but it's only about .25". The short manifolds also vary in length according to make so might be worth investigating if clearance is an issue. 
Slow M said:
That is not correct as far as the DCOE series is concerned.
Best,
B.
There are two type of venturis for weber 40DCOE's (not sure about other sizes). The type designed to accept slot-in trumpets and the type designed not to. The difference is a lip on the diameter of the outside edge of the "non-slot-in-trumpet" venturi which makes the venturi a snug fit in the carb body.Best,
B.
If you fit "slot-in" type venturis without using slot-in trumpets then the venturis can rattle in the bore.
M3.
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