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Old August 29th, 2009, 08:46 PM   #1
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Offenhauser Dual Quad

I was looking through the Offenhauser catalog today and was surprised to see the offerings for intakes that company markets. Has anyone on the forum ever used a tunnel ram or dual quad manifold from these guys on a 455 build? If so what did the build consist of and how did you use it? I'm curious as I look for ways to spend my "hobby money" on a build as to how successful one might be in using one of these unique intakes to make some good usable power both low speed and decent mid to upper range.

Thanks,

Steve
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Old August 30th, 2009, 07:35 AM   #2
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Quote:
Originally Posted by rocket731 View Post
I'm curious as I look for ways to spend my "hobby money" on a build as to how successful one might be in using one of these unique intakes to make some good usable power both low speed and decent mid to upper range.

Thanks,

Steve
Spend a little time understanding how ram tuning works. The intake (and exhaust) tract is a Hemholtz resonator, which means that the length and diameter of the tube govern the frequency at which sound waves resonate in that tube. The valve closing event initiates a pulse in the tube. If you correctly size the tube, the pulse reflects off the open end of the tube and comes back. Timing this reflection to coincide with the valve opening will result in a slight increase in volumetric efficiency and thus power. Unfortunately, the required length of the tube varies with RPM, so any such tuned manifold will have a benefit only at a specific RPM range. The result is that tunnel ram intakes are ONLY optimized for a specific RPM range, usually the upper end of engine performance. This is also why new cars have variable intake tracts so the length of the intake runners can be matched to RPM range.

The Offy low-rise dual quads are even less desireable, in my opinion. Take a good look at one and you'll see that they are simply a large, flat plenum with no internal runners. Flow-wise, this is not desireable. The best use for one of these is to weld on a plate of aluminum and use it as the basis for a 6-71 blower manifold (this is what most supercharger companies like BDS do for Olds motors). Again, the design of this intake is NOT conducive to a broad power and torque curve. If you want a nice street dual quad intake, find one of the long-out-of-production Edelbrock C396 intakes, which is a dual-plane, dual quad intake for a BBO.
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Old August 30th, 2009, 04:04 PM   #3
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Thanks for that insight and I will definately look around for one of those Edelbrock manifolds.

Steve
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Old August 30th, 2009, 04:04 PM
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