For others like me that did not know about IR systems:

Designed to run one isolated barrel per cylinder. This sort of setup is known as an Independent Runner. Holley’s big-CFM Dominator was only a viable wide-band power proposition because of its intermediate cruise circuit and the use of high-gain annular discharge boosters.

Now you know.
It was the set-up the Trans Am Mustangs were intended to use in 1969. The SCCA inspectors saw the set-up and changed the rules making dual carburetors illegal. They are the only Holley carburetors ever made for IR "out of the box".

The carbs are actually under-sized for a 351 ... but they're bigger than 48mm Webers. They are popular with Mopar guys, they're even more undersized for a 426 Hemi!

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That Holley ram system is a very nice setup IF you can fit it into a Pantera.

 

48 IDA Webers essentially are tuned to a certain rpm for a certain size engine. That number is somewhere in the 6200 to 6600 rpm range for about a 351. Tuned meaning in this case, maximum peak power.

They certainly will go over that but the power curve will be flat from there up.

A 351's ideal IR runner is going to be 51mm.

 

One of the things that is not being dealt with is fitting the system to the"chassis" of the car specifically.  In a Pantera or a Mustang chassis, there isn't enough height over the top of the Holley carbs to use stacks tall enough to retain the reversion droplets within the carb velocity stacks. They simply are too short to do that.

When you go to the Pantera with Webers you are able to use 5" tall velocity stacks. That retains the reversion cloud within the carb stacks themselves.

One way of dealing with that though is to change the configuration slightly by using a 1" spacer under the Holleys to essentially modify the intake into a single plenum manifold. That seems to work well enough? What you do with air cleaners as a result though is up to you to invent something.

 

The height of that Wieand intake is going to push the top of the carbs too high in relationship to the roof of the Pantera in the engine compartment to do anything about that. It will run fine, but you are going to have to go to a custom cam profile to "control" that. You can't completely fix it with the cam, just reduce it some.

 

In addition, the term "restrictive" depends on what rpm you intend to run the engine at. If you are going racing with a Pantera, that's one thing. If this is just a killer street car, that's another thing all together.

 

In my own personal experience, Webers with 5" stacks, 180 headers, A3 heads, and the Compcams .605 lift solid cam, first off, it idles at 800 rpm, when you rev it off of idle, it screams like an F1 car. You can't get more, and you don't need it unless you perhaps want to turn it into a Saturn 5 rocket booster for a Moon shot?

I chose to go with Webers. I went through this delema 30 years ago. One of the things that I did discover was that you do not need to cut the decklid to clear the Webers. They clear by about 1/2" without that.

Just all my personal opinions which admittedly are at odds with many others here.

Best of luck on your project.

 

 

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