HI-RAM SERIES: These tunnel ram manifolds are used primarily in drag racing, tractor/truck pulls and performance marine applications where high RPM performance is required. The effective RPM range is between 2,800 to 8,000 RPM. The WEIAND Hi-Ram, with it's patented D-shaped port runners and large plenum chamber, provides optimum velocity of the air/fuel mixture to the cylinder head intake ports. For maximum performance in a naturally aspirated competition application, the WEIAND Hi-Ram is the manifold of choice! This manifold is designed to be used with performance oval port heads.