Offenhauser Dual Port Intake Manifold 258 Straight 6

The Dual Port 360 can best be described by saying it’s actually two separate manifolds in one.  The entire manifold is divided from the base of the carburetor to the head flange.  In operation, the primary mixture is fed into the bottom runners and the engine operates on this smaller port until the engine demand cuts in the secondaries (the top port).  In the Dual Port, the primary system further restricts the air flow after passing the carburetor and increases it to the speed of sound.  This means that even at low engine RPM, it offers near perfect aerodynamic efficiency, which means MORE HORSEPOWER!!!  This intake can gain you fuel economy while also adding 15-30% more power!

This extra horsepower on the primaries comes from a more perfect mixture moving at near sonic speeds, a larger volume passing the intake valve and greater turbulence in the combustion chamber for a highly efficient use of fuel.  The primary system being on the bottom uniquely provides two layers of manifold casting and a high speed mixture flow which acts as a perfect insulator for the secondary runners.  And since the secondaries are insulated from engine heat, this means that when cut in, the secondary mixture will be colder and more dense, a further increase in performance.  Then, when the secondary mixture gets to the end of the runner, it is picked up and rammed into the combustion chamber by the sonic velocity of the primary port.  All of this means less fuel to gain more horsepower.  Also, this intake is proven to lower emissions due to its efficiency in mixing air / fuel.

Uses standard 4bbl carb from 400 CFM to 600 CFM depending on whether it’s for street or competition.

Works great with the Edelbrock 1403 500cfm carburetor!

**NOTES: 

• Works with stock exhaust manifolds, and also works with headers (except Borla or Clifford brand headers).  
• Includes linkage kit, which works with stock stamped steel bracket off stock intake.  
• The carb will be mounted sideways, and there is a cable and bracket to the carb included in the kit.
• If auto, kickdown will work off stock bracket.  
• Holley carbs have a lever that goes up and down, which may interfere with the manifold.  If so, use hacksaw to remove lower part of kickdown to clear manifold.  

• Fits All with AMC 258 Straight 6
• Dual Port Design
• Square Bore Style
• Increases Fuel Economy!
• Increases Horsepower!
• Performs from idle to Redline
• Made in the USA