Single plane vs. dual plane intake. How to compare?

[plovett]

Two intakes:

You have a single plane intake with a smaller cross sectional area and a smaller total volume (about 20% less), yet flow flows much more, almost 20% more.

You have a dual plane intake with a larger cross sectional area, larger total volume (about 20% more), yet flows considerably less on a bench, almost 20% less.

Is the single plane always better because of it's smaller CSA and volume, compared to it's flow?

Can you look at the cylinder head flow and say "enough" intake manifold flow is enough? So the dual plane intake might be best on on lower flow cylinder heads even though it's flow is inferior compared to it's CSA and volume. Does the longer runner length trump that ratio (flow/CSA-volume) on a milder engine? Or is sometimes a single plane just plain better even on a milder engine?

How do you compare cylinder head flow numbers and intake manifold numbers?

Is there a ratio of intake manifold flow to cylinder head flow that is optimal? Or do you look at CSA, shape, volume, length? How do you sort it out?

Sorry for the convoluted question.

paulie

[panic]

Read my comments on my site here: http://victorylibrary.com/mopar/intake-tech.htm

[plovett]

Read my comments on my site here: http://victorylibrary.com/mopar/intake-tech.htm

Nice article. Thanks.

paulie

[HDBD]

I enjoyed your article. You have an impressive resume.

[rustbucket79]

Read my comments on my site here: http://victorylibrary.com/mopar/intake-tech.htm

Ever get a chance to dyno one of the “Rat Roaster” intakes?

[1980RS]

Just did a back to back Single plane vs Dual Plane BBC in Oct. Not much difference between the two intakes. The Dual Plane had a better 60ft. by a few hun and a better 1/8 in the 7.0's, the Single Plane had a better top end by 1 MPH and a slower ET by 1/2 tenth.

[steve cowan]

Just did a back to back Single plane vs Dual Plane BBC in Oct. Not much difference between the two intakes. The Dual Plane had a better 60ft. by a few hun and a better 1/8 in the 7.0's, the Single Plane had a better top end by 1 MPH and a slower ET by 1/2 tenth.

this is exactly what i have found at the track as well

[Mark O'Neal]

In general the single plane will give you higher peak HP, while the dual plane will give you higher average HP.

[n2omike]

If power below 5k matters, a large runner dual plane is usually the best choice in an engine shifted below 6500 rpm... with a remotely streetable gear/converter. 'Large Runner' means just that for a performance application. In Edelbrock language, that would mean avoiding the standard 'Performer' and opting for either the Performer RPM or Performer RPM Air Gap. Their standard 'Performer' line was designed in the 1960's for stock 2bbl engines upgrading to a 4bbl. It was never meant to be an actual performance intake.

[plovett]

Thanks guys!

Is there something intrinsic about dual plane intakes that make more power at lower rpm?

Is it runner length? It is just weird because half the runners in a typical dual plane look about like the runners in a typical single plane. Half are long and half are short. On the other hand, the long runners of the tunnel ram lend credence to the length and ram effect idea.

Is it the split plenum? If so, then why wouldn't split plenum single plane intakes do the same as well, and be more common? Or is the 180 degree split plenum of a dual plane the key? 2 runners to each opposing side as opposed to 4 runners to the same side in a split plenum single plane.

pl

[BLSTIC]

I remember reading about DV saying that it's largely to do with carb booster signal and atomization. When you've got a dual plane it cuts the carby in half and separates every other intake stroke, so rather than 1.5 cylinders drawing from the full carb you have 1 cylinder drawing from half the carb.

A big carb on a single plane will have little to no airspeed through the venturi at low rpm. If you mount the same carb on a dual plane manifold the airspeed through the venturi goes up by around 1/3.

There are other tricks you can do to improve the situation, like vacuum secondaries, annular discharge boosters, detailing the carby properly. All of those will improve atomization at low speeds.

I'd very much like to see single plane vs dual plane with port injection though, to separate the effects of atomization from that of the altered airflow

[1980RS]

I remember reading about DV saying that it's largely to do with carb booster signal and atomization. When you've got a dual plane it cuts the carby in half and separates every other intake stroke, so rather than 1.5 cylinders drawing from the full carb you have 1 cylinder drawing from half the carb.

A big carb on a single plane will have little to no airspeed through the venturi at low rpm. If you mount the same carb on a dual plane manifold the airspeed through the venturi goes up by around 1/3.

There are other tricks you can do to improve the situation, like vacuum secondaries, annular discharge boosters, detailing the carby properly. All of those will improve atomization at low speeds.

I'd very much like to see single plane vs dual plane with port injection though, to separate the effects of atomization from that of the altered airflow

That should work in theory, but this year when I swapped Vortec heads on my 406 testing I put the ported SV on over the GM Bowtie Vortec dual plane I used on the prior heads. I was not sure if this SV intake would work very well being the ports were opened up to the 1206 gaskets and the ports were pretty large compared to the heads. Must have worked, the car ended up running 10.90's that day and really pulls like a fright train to 6200 RPM. Not sure if the dual plane would go better, but after testing single vs dual test on my BBC this year I am willing to bet there would not be much difference there either. Some stuff that you would never think would work seems to be the best thing you ever tried.

[289nate]

When you have a slow ET for the MPH one usually says the car isn’t efficient at the drag strip. Not that it doesn’t have low end torque. Higher MPH drag racing shows potential for a better ET. You just have to change everything else to realize it’s potential. Most people won’t do that because it gets more involved and expensive. Most of the dual plane believers are more street than strip. Which is fine and logical.

I was always surprised how many top guys chose a modified single plane and did well often winning in the early days of the Engine Masters competition. What is best and what is realistic for the average hot rodder aren’t the same.

[289nate]

What year was the Vizzard article? Top notch carburetor builders are properly metering the fuel with much less signal or depression using today’s technology and innovation than ever before.

[Geoff2]

Vizard book 'How to build HP vol 2'.