Thread: Dual plane vs. Single plane

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Thre wasn't a general engines section, so I figured the most popular engine section would suffice. This may belong in another section, seeing as how this is just a curiosity thing, so please move it if it does.

I got this from an old thread.

Originally posted by 390 bracket
Correct me if I'm wrong: Along with a weight savings-(cast iron vs. aluminum)-aftermarket intakes generally will have better flow characteristics than oem jobs. You can get a single or dual plane intake. Single plane intakes are generally used for power farther up the rpm scale. Dual plane intakes generally work better at street usage rpm-showing better low rpm torque.They are much easier to drill for NoS WOOOOOPPAAAAAA

My question is, why are the single planes more suitable for higher RPM's than the dual planes are? I tend to function better when I know the functions of things, so I would appreciate a technical explanation as to how a single plane will change the breathing up top and provide for better performance. I'm just looking for the operational difference in single and dual plane manifolds.

You've got it backwards. Single planes are better for high rpm applications, and dual are better for low rpm.......i.e: street usage.

I don't know all the technical reasons, just that it is so. I't has something to do with flow characteristics at certain rpms, probably.

One of our engine building experts will have the answer, I'm sure.

Thank you, I got my words mixed up.

It has to do with cylinder filling and mixture velocity. With a dual-plane manifold, each cylinder sees only half the volume in the manifold as opposed to a single-plane, where all the volume is seen by each cylinder as it ingests its load of mixture. It doesn't take as long for a cylinder to pull a vacuum in half the volume, so a "half-volume" dual plane works better at lower rpm's due to a faster mixture velocity and subsequent better signal to the venturi of the carb. When the mixture slows down, the carb has a tough time calibrating the fuel to air ratio that it is going to feed to the motor.

At higher rpm's, there is more air moving through the motor and using twice the volume of a single plane is not a problem.

Look through Edelbrock's offerings and pay attention to the rpm range for each individual manifold. Every manifold has a minimum and maximum operating range depending on what you are using the motor for.

Ohhhh, ok I'll have to do some more research as to how the specific designs affect flow, but I get the main idear now. Thanks a lot Richard.

Richard (Tech) will fill in the spaces that I miss and straighten things out, but here's my take on it.

Dual Plane(180 degree)-Divide the V-8 into two four cylinder engines. The V-8 has a firing pulse every 90 degress. The dual plane runners connect the cylinders that fire 180 degrees apart. Two barrels of a four barrel carb feed two cylinders on each side. Therefore, some runners have to pass under other runners, making it have a high and low plenum, which is the open area under the carb. The high plenum feeds the runners that cross over the runners from low plenum. The high side has a fairly easy job of getting the air/fuel to the cylinders because of it's height but the low side has a little difficulty, which in turn, results in a restriction in upper RPM levels. Also, a dual plane halves the amount of carb seen by each cylinder which limits the air/fuel needed in higher RPM levels. The reason they are better for low speed operation is that by splitting the carb/induction into half, the volume to a single cylinder is also half. This results in much less dampening of the intake pulse which leads to a much better booster signal at the carb. That results in a much better fuel atomization at low engine speeds, which means better low end torque and gas milage.

Single Plane (360 degree)-The single plane intake has a common plenum that is shared by all cylinders. This dampens the intake pulse at low engine speeds, resulting in poor fuel atomization. Also, the runners are much larger along with the plenum, therefore dramatically slowing down the velocity in the runners going to the cylinders. On the other hand, once the engine speed is in the upper RPM's, the larger runners, along with the larger plenum volume let's the engine breath all it wants to on the intake side.


High performance street engines are all about compromise. The better of the intakes on the market today that is a true performer of both aspects of this is the design of the Performer RPM Air-Gap manifold. It has high runners and a dip in the divider under the carb.

both you guys tech camaro68 did good job better than i would

Another interest that I have been wanting to experiment with, just lacking on funds, is the IR systems. The sponsor of this site, Inglese is a maker of these systems. They have individual runners and carbs to feed each cylinder. They break it down to where the V-8 seems as if it is 8 one cylinder engines. It will take a fussy, big cammed engine and make it idle like a fuel injected stocker. The overlap syndrome plays no part in booster signal loss. Engines equipped with these systems will generally make more low end torque and hp but are limited to the carb size and throats of the runners. A bit of a pain to tune I would imagine but that's half the fun.

Well, the Inglese system sure are job security for the carb tuner!! The Webber setups on the 289's in the Cobra's and Mustangs made some great horsepower in their day. Would be a fun dyno exercise to see how 1965 Technology stacks up against 2006 Technology!!!!

Appreciate the help camaro, your signature holds true