Vlad,

I was throwing out some old books in the hangar and I ran across this
Holley book published in 1976. Nothing new under the sun.

Paul Lamar

"Independent-runner Manifolds-"

"Independent- or isolated-runner (IR) manifolds
are race-only devices with one carburetor throat and one manifold runner
per cylinder-head inlet port."

"Carburetors used in IR systems must be much larger than for other
manifold types because each cylinder is fed by just one carburetor
throat or barrel. Another reason for needing a larger carburetor is
the severe pulsing in such systems reduces carburetor flow capacity
in the RPM range where standoff becomes severe. In any IR system,
some method of standoff containment should be used."

"Plenum-ram Manifold-"

"This "almost-IR" manifold uses a plenum chamber between the carburetor
base and manifold runners.  This chamber helps to dissipate the strong pulsing
so less of it enters the carburetor to disrupt flow. Just as important, it
allows the cylinders to share carburetor flow capacity. In the typical dual-quad
plenum manifold, three or four cylinders are simultaneously drawing mixture from
a plenum being fed by eight carburetor bores.  The sharing of carburetor capacity
allows the plenum-ram approach to manifolding to be "very forgiving" in terms of
carburetor capacity so long as the carburetors are not too large for the
RPM range to be used."