Send him the pic of your stacks. It might help him.
I don't know how the 51mm designation on yours effects the situation?
The picture I posted should fit yours. At least the bolt pattern will and the trumpets themselves appear to be the same ones that I have.
IF your intention is to attach the screens like I have then you do not want the rolled over edges on top. There is no "flange for the rubber ring to attach to like on mine.
You are going to have to do something with keeping water out of all of them but mostly on #4 and #8. Those two will be completely exposed since the roof does not cover them.
The others although they are open as well are tucked up under the roof.
You just have to wash the car from a garden hose carefully with those. It can't go into a carwash any more (as if it ever did).
The Pantera "sugar scoop" roof spoiler that came on th L's becomes functional with an IR induction system especially with tall ram stacks like this. It directs the air coming over the roof into the intake area of the stacks.
The taller stacks also change the frequency of the sound that the engine makes at full throttle. I suppose it is like playing a trombone which has a slide tube to change the notes it plays.
Someone had actually done a flow test on these things and said that the wider mouth opening increased the flow through each runner by 25cfm over the stock Weber stacks. It seems like a lot but there is logic to a reduction in restriction of flow.
I think it was one of the VW people but they don't use the tall stacks like this, just the wide mouth stacks.
How this effects a TB system, I don't know? You will find out.
On 48 IDA's you can change the "venturis" and that does effect the flow of the carburetor.
Stock, IDA-4's come with 37mm "chokes" (venturis). The Ford GT40's used 42mm ones and those carbs were designated as IDA-1.
This is all with 48mm throttle bores. Yours are using 51 mm throttle bores so those give the engine different characteristics in where the "torque curve" comes "in" as does the id of the header tubes and their lengths.
WEBER says the 48 IDA system with 37mm chokes flows 2400 cfm. 300cfm x2 x 4 carbs. That is 300cfm per intake throat. That is right around where you want them but is becoming restrictive right there.
42mm would be better putting the system right around 320-330cfm especially with a less restrictive "trumpet". Now you can see how changing these parts "tunes" the intake flow and power range of the engine?
This is also where the lift of the camshaft has to put the intake flow of your heads into the 300 to 330 cfm vicinity. That information is determined on the flow bench.
From what I have seen the lift of the cam needs to be .600 or more and lifts over about .630 no longer are adding any contribution to that flow. They are just adding unnecessary stress to the valve train? BUT even if they did, the induction is already at it's limit and maxed out.
ALSO, I too am using that Hall Pantera intake manifold. Even though a 51mm throttle plate will flow more cfm, the manifold runners are at their limit somewhere right around there (as cast). The runners right under the flanges need to be worked in order to use the additional flow.
On mine, that flange was as delivered machined exactly at 48mm.
On yours, you would see that immediately when the TB's were off for the o-ring repair. You would see on the mounting flanges where there was work with a die grinder done AND the throttle plate opening in the intake flange enlarged to 51mm.
I have had BOTH of the Hall manifolds and there is a diffeence in the casting between the original 4v head manifold and the A3 "raised port" manifold. You want the "raised port" manifold. It has better line of sight to the intake valve but that only matters if your throttle plates open on the inside rather than the outside of the port. You gain throttle response opening on the outside.
If you noticed the rpms used in the youtube of the blue Pantera on the track, it never goes above 6700 rpm and rarely below about 4,000rpm. That is where that car is "tuned".
Simply put, you do not need an engine that turns over 7,000 rpm. As tuned it will even pull with a 427 which is what I said about driving a 427 Cobra and a Gp4 on the same day.
I actually thought the Pantera was faster. It certainly was dialed in better than the Cobra was.
With a Pantera with IRS, independent runner system induction, you are actually tuning the system to the car and the way the engine and induction fit into the body of the car. If you put this exact system into another body and chassis, you need to start all over again. It will not be the same solution and it will not give you the same results.
OH! Almost forgot! There was an Aussie selling stacks to fit both setups on Ebay. His solution was to take a 48 IDA stack and make bolt on flanges that clamped the stack to whatever you were using. That made the stack a modular system by the adjustable bolt on clamps.
Trouble is I can't seem to find the guy now? I will search again later.
