individual Weber screens

[Jim Pearson]

Can any of you explain (in simple language, please!) the effect of the taper and length of the trumpet - I think I've been told that a longer trumpet will yield more torque, although if this is the case there's presumably a trade-off.

I'm just wondering what the downside of a pronounced taper would be - in rough figures, a 70mm diameter has twice the surface area of a 50mm. So could a solution to the mesh question be a large diameter, highly tapered, trumpet carrying either a flat (as Peter D suggested) or slightly domed (as per Bernard's first photo) mesh? Although, if I understand StanJ's point correctly, there will always some reduction in efficiency whenever mesh (or other filter medium???) is employed.

Stan, wot's WOT?

Jim

[ChrisL]

Restricted surface area is not the only issue. As I understand it, the air flow around the top rim of the trumpet is important so by fitting these tea strainers you will alter the air flow and lose some performance.

But having said that, I've been using these tea strainers now for a few years with some track work too and the difference in performance is not dramatic. I couldn't "feel" the difference but it probably could be measured on a dyno or with a stop watch.

The question about grit and the reduced life of the engine is a good one too and was something that did play on my mind. I also get asked the question regularly so I'm constantly being reminded. But I figure if it lasts 50,000km between rebuilds, that would equate to six years or more for the amount of driving it gets. And lets face it, these engines in road trim don't cost all that much to freshen up. Incidentally, I have done about 25,000Km so far after three years and the engine is just starting to feel like its loosening up, so I think it has a long long way to go before it needs a rebuild (I hope these aren't the famous last words ).

[Bernard]

Originally Posted by delaneyp

... how did you do the clamping rings, & are they removeable ? ...

Hi Peter, I will try to explain to you through mi vague language how to proceed to do it. However, I have to say that the medium result don't justify the time that you will spend to do it. The mesh is crimped on the trumpet with ring of aluminum sheet cutted because the trumpet is made of cast aluminum and it is not easy to weld the mesh on. You need to made your own special tool (see pictures) and to use a press to bend an aluminum sheet (0.03" of thickness) like an angle ring (3/16" x 3/16"). Then, you have to cut a circle of mesh (3" of diameter) and to place it in your special tool between the angle ring and the trumpet. With a small hammer, you have to bend the angle ring to crimp the mesh below the trumpet. Then with a cutter (or better a Dremel), you cut the excess of mesh wich extends the aluminum crimped ring. This screen is not easily removable but it is possible to do it. You have just to cut the aluminum crimped ring
On the picture 1 you can see 3 Weber horn for IDF carb
- Number 1 is original made of iron sheet
- Number 2 is after market made of cast aluminum
- Number 3 is an original model that I have modified to increase the hood clearance (I have a Cobra car, not a GT40 ).
On the picture 2 is the special tools you need. Internal and external diameters shall be adjusted according to the trumpet larger diameter and your aluminum sheet thickness.
My first test on picture 3 (not very nice )
Picture 4 is my lath that I use like a press to crimp the aluminum ring

[Howard Jones]

I think that one thing that has been missed, or at least I missed it, so far is that even if the restriction caused by the screen is 50% you can still flow 100% by increasing the screen area by double.

This can be done by making the opening in the screen through which the air must flow bigger and shaping it like half of a ball much like the set on the DFV seen above in this thread.

The worst case is a flat screen stretched across the top of the trumpet. Some of the strainers used must be at least 50% restrictive and likely much more so. Not to say that they don't work somewhat to keep out large pebbles but they certainly don't do anything to prevent engine wear due to ingesting dust.

As far as how long they might reduce engine life. Consider a trip of 100 miles down the freeway. Nice clean air, no dirt in the air etc. As you arrive at your destination you must turn off the highway onto a less traveled road and at one point cross a few yards of dusty road left by a homeowner digging a new planter.

Those few seconds of dusty road will produce more wear than the previous 100 miles.

I know they really look good, I love the look of a set of Weber's with velocity stacks on them but a good quality air filer is the way to go.

Somebody a couple of years ago had a clear box with filters elements in the sides of it covering up a 8 stack setup. Very good idea. A oval turkey pan with a clear top and sides made of filter material would also work very well. Much less restrictive also. If I ever can afford a set of Webers thats what I'm gonna do.

[Bill Musarra]

I have the TWM setup, and I thought the dimensions you guys were giving were a bit small. I measured mine and got the dimensions in the pic. At 3 1/4" at the lip, I figured the strainers were not going to work out for me. I went on a Google search for "tea strainers" and got a lot of hits. Unfortunately, there were few that would tell you the size other than tell you it would fit the rim of a cup. After a while I found this site.

Tea Infusers, Strainers & Accessories

They give you the different sizes of the strainers. Some in two or more sizes. There are a couple that will work out, but for attaching them I think it will involve a tiny sheetmetal screw in the rim. I don't have any fabrication skills for fitting a rim to the stacks. So I will have to use either some silicone or the screws. Some of these handled ones might be altered to use part of the handle as a hold down???

Bill

[Pete.]

I have been using the orange foam sock type filters, which are effective but look horrible.

After reading this thread I spent last weekend making up the tea strainer type which look terrific.

Now after reading Howard's post I am worried about dust and wear.
Has anyone had a long term experience with the tea strainers?

I'm not talking track cars that do an engine freshen after every couple of races, but long term road use.
I seem to be clocking up about 5000 miles per year on mostly bitumen.

[Andy Besic]

Pete,

How often and how much dust are you cleaning out of the deck under your rear windscreen? I would think that would be a good indicator of how much "stuff" your intake is subjected to.

I never have run anything on my sidedraft weber Alfa Romeo race car. I rebuild every couple of years, but it seems like everything else wears out faster than the piston sleeves and valve seats so I figure if I keep the kitty litter and parts falling off the english cars I'm lapping out of my trumpets, it's all good!

Andy

[Pete.]

Thanks Andy,
I don't seem to collect a lot of dust in that area so it might be OK. Having said that I am a compulsive with the dust rag so it doesn't get time to build up.
I was thinking back to my younger days and remember that most of the bikes I had in those days ran side draught Amal's with no filter, and I cant remember any problems.

[Doc Watson]

Pete, put a filter element in the side inlets... that should help some... any photos of your tea strainers? my MKII tea strainer should be with me tomorrow.

Andy

[Pete.]

Originally Posted by Doc Watson

Pete, put a filter element in the side inlets... that should help some... any photos of your tea strainers? my MKII tea strainer should be with me tomorrow.

Andy

Hi Doc, I'll take some when I get home tonight.

[Pete.]

I ducked home at lunch time and took some photos, the first is the orange foam socks, the rest are the tea strainers and the last is while I was at it I fitted stone guards to the side air inlets.

[John Fitzpatrick]

This is the filter type I have now. Wide thick mesh and held in place by molded rubber rings. The second two photos show the box the strainers come in and what they look like.

[John Fitzpatrick]

I ground off the thin clasp that holds the two halves together and the chain loops using a Dremel & grinding stone. I tried a burr and a cut-off wheel but the stone was quicker and easier to smooth with. One note- I held the disk in a vice the first time and that left a crease in the soft metal. It’s much easier just to hold the part in your hand while you grind. It took about five minutes to do the whole part.

The box reads 6 cm which would be 2.36 cm, but that’s the ring ID. The outer lip of my bell is 2.95 in, and these fit perfectly. I have extended length stacks though, and I don’t know if my diameter is common. The strainers are available in different sizes- just keep in mind the size evidently refers to the sphere diameter, not the rim.

To attach the screen to the stacks I used blue RTV gasket maker. I considered several other adhesives, but I think the silicone will hold up well and I won’t have to worry about a set screw or chunk of epoxy coming loose and going through the carb.

[John Fitzpatrick]

This is the final result. The strainers I used were from acme_kitchen (no affiliation with me) on eBay and cost $7.50 a pair ($15.00 for 8 carbs). I’ve asked the owner if she’ll give board members a discount, and if she will, I’ll post details here. The only real downside I see is that the mesh is fine and softer than the thick screen I had—about what you’d see on a window screen. At that price, it wouldn’t be a bad idea to get an extra set in case you need a replacement.
John

[Jonathan S]

This string reminds me of a string on the ffcobra forum. One guy made a filter a lot like the top one in John Fitzpatric's post only with a paper element he cut out of a larger air filter with a wire mesh to reinforce it. His goal was to get finer filtration then just a wire mesh. One day he popped the hood and one of the filters was gone. The whole thing got sucked into the engine and made its way past the valve one piece at a time.

[MReid]

Jonathan, I think he said he watched with great dismay the element get sucked through the wire mesh as he was working the throttle with his hand!

I'm using the restrictive wire mesh filters on my stack EFI and I notice a big difference in afr on my wide band when I remove the filter. It went from .95 lambda to 1.02 at idle. Here's a pick of my set up in my coupe. I want to use the same in my GT40, but I have the same concerns people in this thread have about air flow: