Chrysler Mopar BB 413 426 440 HiRise Aluminum Intake Manifold [Black] The main difference is that

The main difference is that there is an open area under the plenum chamber

Featuring high strength Aircraft Grade Aluminium which is lightweight

Nitrous/injector bosses

The outer case is made from 8620 Chrome-Nickel-Moly steel and the case hardened for long life

and excessive emissions

Chrysler Mopar BB 413 426 440 HiRise Aluminum Intake Manifold [Black] The main difference is thatStep up to the high rpm power of an open plenum with Speedmaster HiRise intake manifolds. These cast aluminum manifolds accept square bore carburetors and are pressure tested to ensure maximum performance. They start to make awesome power around 3,000 rpm.