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Last weekend at a swap meet i saw an intake manifold made by offenhauser to suit 4V Cleveland. What intrigues me is that it was called a Dual-port and and had a horizontal split in the port and the internal plumbing of the manifold was weird. The bloke selling it said that it had all the low-end of a dual plane with all the top end of a single plane.
My question(finally) is does anyone have info on this manifold and does this dual port stuff work.
 

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I went Offenhauser hunting a while ago for a P.O.Sonic. I turned up a couple of dual ports for a 460. Each one had had the guts ripped out of it (die grinder in ports and dividers removed.
In theory they should have a higher air speed when primary butterflies only are open as the plenum area is halved for those butterflies. In practice everyone seems to gut them so who knows if its good in real life??
 

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I experimented quite extensively with various intake manifolds on a 4V Cleveland about 10 years ago. Out of all the manifolds I tested the spread bore Offenhauser Dual Port made the most low end torque and got the best fuel economy of them all. I tried, the stock dual plane, the F351-4V/Perfomer, a Torker and the Dual Port. It was basically finished at just over 5000 RPM though and I gained almost 10 MPH in the 1/4 when I switched to the Torker. The Dual Ports fuel economy, torque under 3000 RPM, and throttle response, was unbeatable however. I also had a Dual Port on a 351W in a Mach 1 when I bought one a couple of years ago. Again, I found the throttle response and low end torque to be very impressive, but the power was all in by about 4600-4800 RPM. Swicthing to an Edelbrock Performer lost some low end torque below 2500 RPM, but allowed the engine to pull hard to 5400 RPM and picked up 4 MPH in the 1/4. I hope that helps.
 

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Here’s another manifold question. I have a Ford inlet manifold (even has the firing order stamped on) on a 69 302 Windsor that came with the car when I bought it. It also has the horizontal peace in the initial chamber. The manifold is a high-rise type for a 4bbl. Anyone know what it came of off and how good it is.
 
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