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Chrysler installed the “active intake manifold” that varied the length of the intake runner “to expand the engine’s torque and horsepower range” on some, but not all, applications. When it’s activated, the butterflies in the intake runners open up at 4,000 RPM to create an intake path that’s half as long, so the engine makes an additional 25 horsepower without losing any torque and ends up with 390 horsepower. You can actually feel the difference when the short runner valve switches over in my pickup truck.
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https://www.knowyourparts.com/technical-resources/engine/57l-hemi-anatomy/It is possible that cutting a second entrance in the bottom of the intake runners of the beer barrel Magnum intake manifold would create an improved performing manifold where the airflow “would decide for itself which opening to enter” based on rpm. Ford discovered something like this on an intake that originally designed with a mechanical valve to vary runner length. Ford engineers discovered the airflow “naturally” chose the correct entrance. I cannot tell you the shape of that new entrance: maybe round hole, maybe centered rectangular slot, maybe offset long slot on the side that enhances swirl.
The beer barrel Magnum intake was designed for the Magnum 5.2 and suits it pretty good.
I speculate that the 5.9 V8 needs runners that are greater in cross sectional area, and double resonate, ideally at 1700 and 4100 rpm.
I thought the 0.69 overdrive of a 46RH is right for a 5.2 Magnum,
but a 5.9 V8 needs a .62 overdrive
and a 8L V10 needs a .50 overdrive
To the original poster instead of small mods to a Magnum 5.2
he should consider transplanting in a 5.7 Hemi.
Way greater bang for the somewhat bigger bucks.
