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This car came with small velocity stacks that integrate with twin air filter boxes. I decided to sideline that setup and try these big velocity stacks. I plan to fabricate air filters for each stack and will use debris screens in the interim. The EFI is TWM throttle bodies on a Weber manifold by Hall Pantera. The ECU is Holley Terminator X. This car is a Pantera project that I received in February last year. It is a 1972 Pre L that is setup as a GTS.

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Last edited by stevebuchanan
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Thanks for the link to PJ Motorsports.  I had not seen that before and they have good ideas.

The stacks are from https://dansperformanceparts.com/

I had to fabricate the stacks.  My TWM throttle bodies are similar to Weber 48 IDA carbs but do not accept slip in stacks, only bolt on units.  I bought the set of 48 IDA slip in race stacks along with a set of cheap steel stacks for Weber 48 IDF that bolt on like the ones that came on the car.  I sawed off part of the horn on the bolt on stacks allowing the race stacks to slip on.  It resulted in a mostly snug fit and I secured the joint with an ample amount of Ultra Black silicone.

I came across someone that makes nice billet stacks for my application but they were nearly $1,000.  I'm not certain they would actually fit.  I spent about $250 on the setup you see here.

For the time being, I am using these aluminum debris screens that fit under the stacks.  I notched them with a rat tail file for bolt clearance.   I have some stainless equivalents on order.



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I have 5" tall aluminum spun stacks on Borla throttle bodies.

They came out of one of the VW aftermarket shops.

They are from my 48ida's and had the extended skirts that extended into the carbs, like yours did. Those don't work with the throttle bodies.

As with yours, those needed to be removed,



What I did was simply machine 1/8" thick round aluminum flanges and aluminum solder them on to the stacks. Some call that aluminum welding, but it is more like soldering then welding. It is at a much lower temperature then welding is.

The flanges that I fabricated were drilled with two holes that match the mounting stud location and then at that point just bolted them on.

I was not convinced that silicone or using any kind of adhesive would be dependable, so I went the addition step.



When talking about screens, the flat screens tend to be restrictive. So you need to consider the coarseness of the fabric/mesh.

Also, even though you may find the best balance of filtering ability to air flow with a different mesh then I used, the more surface area that you can provide to them, the less restriction you will have.



This is a picture of what mine look like installed. The black bands you see are the "rubber o-rings" I used to retain the screens. The shape that you see of the screens is a result of increasing the surface area the most that was practical for me to reduce the restriction to air flow of the screens themselves.



The other thing that you need to consider is how are you going to protect the stacks from water. AT LEAST the last two are "out in the weather".

You may be thinking that, "I will never drive this car in the rain". OK, but are you going to wash it?

In my case, the increased height reduces the ability of the stacks to suck in water since they are within 3" or so of the bottom of the roof and also in my case, there is a clear Lexan shield (roof) extending over the stacks and made integral with my louvers.

You can't see the Lexan in this shot because it opens with the deck lid and the deck lid is up.



Remember, you cannot compress water and if you suck it in, you can bend the connecting rods and if you do. likely crack the cylinder walls.



I'm not posting in criticism of what you have done, just trying to give you more information for your solution and help it.

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Last edited by panteradoug

Oye! I have actually seen people do this to cars at shows when they see open stacks. The Devil never sleeps. Serious consideration should be given to a method of vermin elimination to ensure that they can never reproduce and spread their curriculum with personal seed. I think instant vaporization should be considered as appropriate and  in order?

You have to cover the tops of the stacks for your own good to protect from that kind of a malignancy.



Back in the day I saw the Formula 1 cars with tennis balls in the stacks when parked in the pits.

Even the GT40's had a cookie tray mounted over the top of the Webers. You can decide what you think the reason was but I suggest that there was more then just one reason.



Both of these are stack drop ins and are stainless steel so if you don't like them you can use to strain the pulp out of your morning orange juice. That's what I told "wifey" what they were for anyway.

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Last edited by panteradoug

My stacks are 3.73" diameter.  The seller cautioned that there are not any filters available for them.  I will likely have to fabricate screens or filters.

Also, some of the screens and filters are pricey.  Some are about $100 each.

Another option is a plexiglass shroud.  Here they are on Ferraris.



They have no mice in Italy to climb into the stacks and nest there while you are not watching over the car. You need screens.

You can get those plexiglass covers at one of those "all you can eat restaurant buffets".

Just wait for the owner to walk to the back and take one and slip it under your coat. That's how I got mine. It was from a Chinese restaurant, not a Ferrari.

Just another Chinese racing part.



Do mine look like I bought them somewhere? The screen is easy to form. You just wind up with stuck finger tips for a week or so. Stop wimping up.

Last edited by panteradoug

Those shapes are not very hard to make

just make the plug like you Want it Make it nice and smooth, Get some plexiglass or Lexan (I like it better to work with) clamp the sheet into a frame…

build a table with a hole in the middle to hook up the hose of your shop vac…set the plug with little spacers on the table over the hole..

Hold the frame with the Lexan  horizontally and heat it with a heatgun gently up until the sheet starts bowing evenly down..

now take the whole frame and gently put it over the plug.. Frame touching the table all the way around evenly and turn on the vacuum cleaner… puff - done..✅

just trim..

Last edited by LeMans850i

Many of the racers do it all the time making various clear scoops. I suppose that they all have their own secret methods?

I know that there are variations in the formulas for the various Lexans but this is all just another special technology offshoot.

I don't know who is going to make that Batman helicopter cabin bubble, but as Bob Dylan once sang, "it ain't me Babe! It ain't me your lookin' for Babe".

I made my simple clear scoops and it ends there. For good. I'm too complex already. I even scare me.

Last edited by panteradoug

Have you searched ITG and Pipercross? They both make a range of high flow foam filters used in race applications.

If you want the velocity stacks visible for aesthetics it restricts one to using the mesh style cap filters with limited functionality, however the Chinese design shown above using a foam sandwich which is the diameter of the top of the velocity stack will likely be too restrictive in flow. The alternative is to cover the stacks with either single filters that the stacks sit inside or as a group. Making a Lexan top to see them is then a lot easier.GT40 Air filterPantera air filter

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Last edited by joules

The plenum shown is a viable solution for a "street driven car", no question, BUT anytime you go to a IR induction, you change the "sensitivity" of the signal to each intake.

When you enclose them, you have altered that sensitivity again.

The stacks just do not like any kind of a flow restriction.

The plenum that you are creating there, over and around the stacks, needs to be "tuned".



It is possible that this one pictured is right on the money but the answer to that is really that it will vary according to the rpm target of the engine.

In other words, the size of that plenum may be perfect for an engine operating up to 5,000-5,500 rpm and then it gets restrictive and operates as an rpm limiter?



We clearly can see that on the Ford COBRA oval air cleaners on the carburetored induction systems where beginning at about 5,000 rpm, those air cleaners start the restriction and virtually can't flow enough to go much past 5,500rpm.

That is easily shown by opening the air cleaner and just leaving the base plate installed. Then you can rev to the rpm limit of the engine.

A simple way to detect a change would be an improvement in the 1/4 mile time of the same car. That resulting air cleaner change would show a horsepower gain in the 80 to 100 hp vicinity, depending on track conditions such as traction  but make no mistake, that really is a large improvement just by unrestricting the engine induction with no other changes.

As I recall, just taking the air cleaner off of a pretty much stock 428cj Mustang results in an improvement in 1/4 mile times of about .3 seconds faster time.



That is exactly what has been done here. The air box has created a restriction.

To run something like "the Silver State" event, you will need to take the top off of that "air cleaner assembly".



In the case of putting air cleaners on the Weber 48ida system on a V-8 engine cam'd with anything more then about 28° of "overlap", you WILL get fuel reversion that WILL soak the air filter element and IT WILL catch fire on HOT ENGINE restart.

With EFI you can  put air filters on the stacks,  because with an IR EFI there is no atomized fuel retained in suspension in the "venturi" to be pushed out in the instant reversed flow, since the fuel is "squirted" directly into the intake ports.



So the simplest thing to do in a Pantera is to use tall stacks that come within the minimum clearance over the top of the stacks (which is the outside diameter of the stack) and  the roof of the engine compartment and screen the stack using the largest surface area of screen over the stack that you can fit in.

That is going to be the best combination of compromise you can get.

Additionally, the "bell" on the velocity stacks isn't there for decoration. It is there to work like an "Event Horizon" on a "black hole", accelerating the incoming air for more ram effect.

If you block that, you negate that effect.



The GT40's in the day running "Webers" just put a "cookie tray" over the carb stacks for two reasons. First, It prevented anything large from falling into the stacks and secondly, it provided a way to control the reversion fuel droplets from accumulating uncontrollably all over the engine compartment including the rear window and the bundle of snakes headers.

On the GT40, the entire rear engine compartment is the "air cleaner"



If you are building an air box of any kind over the stacks, you are just building an induction system for show, and not go. That is the reality.

It is going to have induction restriction. The only question is where in the rpm range it begins to appear and how much it restricts the engines top rpm capability?

Last edited by panteradoug

@panteradoug is very right…all of the above…

So the question to ask is really what you want … “race car” performance all the time or nicely clean filtered air for longevity or change the setup as needed…

I personally struggle with the decision…

BUT you got that system for the car so I would guess you like it and being expensive I would say A Lot!

Leave it and live with it… It’s like a yellow Pantera. It looks great in yellow, but a cop can see you from a mile away… Still wouldn’t change the color.

people are gonna look at it and admire The set up and thinking “I wish I was that reckless…”

Last edited by LeMans850i
@LeMans850i posted:

@panteradoug is very right…all of the above…

So the question to ask is really what you want … “race car” performance all the time or nicely clean filtered air for longevity or change the setup as needed…

I personally struggle with the decision…

BUT you got that system for the car so I would guess you like it and being expensive I would say A Lot!

Leave it and live with it… It’s like a yellow Pantera. It looks great in yellow, but a cop can see you from a mile away… Still wouldn’t change the color.

people are gonna look at it and admire The set up and thinking “I wish I was that reckless…”

I think that it isn't so much that one needs to decide, "show or go"? It is more a question of what compromise you make and therefore which you deem more important.

Frankly I know of one person in particular that has run Webers on a 289 Cobra for something like forty years with open stacks.

I wouldn't recommend that for a dune buggy or driving in really dusty climates but running filters on these things to me, from what I have seen and experienced is over rated big time.

To me, the point of having all of those stacks is, "lets play and catch me if you can".

To each his own though. Life is short. Enjoy it while you can.

Last edited by panteradoug

My car came with filters but I prefer the look of open stacks in this case.  I currently have temporary screens in the foot of the stacks.  I am thinking of replacing those with less restrictive, coarser permanent screens that will at least catch nuts, bolts, washers, gravel, etc.  And then purchase or fabricate a set of snap on filters that will likely be somewhat restrictive.  That way I can run open or filtered stacks depending on the outing.  

Below are photos of the filters that came on the car.  I still have this setup in a cabinet.  They are quite nice.  The prior owner had them ceramic coated when the engine was being rebuilt.  He then ran out of money and I picked up the project.

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That's exactly what I have now.   I have one piece filters that don't fit right.  If I center them they cut off about a third of the throttle bodies at both ends.  That's why I thought I'd use the ones like Joules is using. When I had the Webers on I used 5" stacks with filters on top, but now with the EFI I wanted tom use full filters.    Nice car and great pics!

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