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Old 01-04-2003, 01:12 PM
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Post Single plane and duel plane manifold

What is the difference between the two... I noticed on desktop duel plane gives me a flatter tourque and hp curve whereas single plane gave me more hp and tq but less at low rpm... I think duel plane from the numbers is best for me but what is the difference?

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Old 01-04-2003, 02:12 PM
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As the name implies, a dual-plane manifold has the runners divided up into two planes, and the manifold separates the carburetor in half. This allows the use of longer runners, and makes a stronger booster signal at the carburetor for better fuel atomization, low speed torque and driveability. Generally the runners on a dual plane manifold are not humongous to help keep mixture velocity high. Some dual planes are designed for street/strip type driving and utilize larger, longer runners to help top end air flow.
A single plane manifold, has all of the runners drawing off of a common plenum, and more importantly, this allows each individual cylinder draw fuel/air from the entire carburetor, thus giving it clearly an upper RPM breathing advantage, of course there is a trade-off here, that being the increase of pulsing, and mixture problems at low engine speeds, making a single plane manifold pretty temperamental on the street, there is a decrease in booster signal at slow engine speeds, and the resulting drop in low speed torque output.
I've noticed that the new air-gap manifolds have a small notch out of the plenum divider, which is an old hotrodding trick to help a dual plane make a little more top end.
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Old 01-04-2003, 02:26 PM
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dual plane intakes are designed for low and mid-range power by using two distinct and seperte plenum chambers to feed two differnt induction paths. These runers tend to be long and small in diameter. This enhances the low and mid-range power. the disadvantage of dule plane limits top end horse power because of the small diameter runners. two good dual planes are the edelbrock performer rpm and the holley contender. Singel pane intakes have large plenums or open chamer directly beneath the carburetor. this plenum directly connects all of the intake manifolds eight runners. They usually have more upper rpm power but sacrifice some low end power two of the most popular are the edelbrock victor jr. and the holley strip domiator. dual plane tend to work better with mild performance small block combined with camshaft durations 225-230 at .05 single plane work well with durations of 230 and above
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Old 01-04-2003, 03:08 PM
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Mostly Dave the big difference is volume, a single plane manifold has a large volume of A/F mixture to get moving and consequently more capabilities for high rpm power due to less restriction. I have used both and what I have gathered over the years is if you are careful not to choose too large of a single plane manifold there will not be a low rpm loss of power. Generally the industry has shy'ed away from these kinds of manifolds because magazines have said over and over that dual planes are better for the street. Are they right? I guess if you are comparing race only single plane manifolds to street oriented dual planes you would be right. The problem (to me anyway) is the two are not comparable, they are apples and oranges. You can't just throw a carb on a single plane manifold and then throw the exact same carb onto a dual plane and compare the results...which is exactly what magazines do.

A single plane manifold needs lots of fuel to raise enrichment in the manifold to a point that lean backfire will not occur, this is easy to accomplish with a double pumper with 50cc pumps and big shooters. Stick this same carb onto a dual plane and it is way too much fuel. The trick is a single vacuum secondary will still work OK on single plane but works far better on a dual plane, as a consequence the single plane manifold seems like the loser on paper and the dyno until you hit the upper rpm ranges where it's superior flow shows.

Components should be matched and a vacuum secondary carb on a single plane intake is just not ideal, you need lots of fuel to enrichen that large store of air in the plenum and keep enrichening until the rpm starts to get the air moving. If you could measure mixture strength in the plenum at the point where load is high and rpm low then you would most likely see the single plane manifold running relatively lean compared to a dual plane. I'm talking about an rpm range now not just the instant where the throttles go wide open.

In the car the effects are obvious, a single plane manifold will seem lazy at low rpm compared to a dual plane but that is because of carb tuning and selection as much as stagnant flow in the plenum. In two identical engines if you optimized each carb/intake combination for that engine you would find that there is very little loss of power (at low rpm) if both setups were optimized. Of course the dual plane would fall on it's face at high rpm right where the single plane starts to feel it's wheaties. This is especially apparent on engines that are cammed in the 280-290 degree duration range and larger, you would find the gains to be had with a single plane on engines with big cams more than offsets the small loss of torque/HP at low rpm.

The thing I laugh at the most is the dyno sheets that show how much better the dual plane is at low rpm and this reason is enough to choose the dual plane. My question is how often do you need that extra 10 ft/pds of torque at 2500 rpm? The reason you hotrod the damn thing to begin with is to improve the high rpm power and if you wanted more power you would downshift...RIGHT! If you wanted low rpm pulling power then put a big block in there and leave it stock...enough said.

The other factor in the single plane manifolds defense is that added kick you get out a radically cammed engine at high rpm, it is nothing to sneeze at. I would compare it to the feeling you get from a two stroke engine coming up on the pipe. This effect is mostly absent on dual plane manifolds because you are reaching the limits of flow with this design and are not making use of the resonance effect apparent in a single plenum design. The feeling from the drivers seat is that the engine is falling flat on it's face or just seems to flatten out with a dual plane design.

Of course nowadays I see dual planes with a cutout in the center of the plenum divider which basically makes it a b@sterdized single plane if you ask me, it does help high rpm power somewhat I will admit. I don't know what to tell you Dave, single planes are "race" manifolds designed and tuned to give you that extra kick at top end, dual planes are "street" manifolds designed for economy and excellent drivability as well as some added power. No one I have converted to single plane manifolds ever said to me they were disappointed with the results, always the opposite. Typically some guy comes to me with his cammed up Mustang or Camaro rumpity rump into my yard and wants to know how to build more power under the hood, once the hood is opened there sits the usual Performer intake and carb package (Nothing wrong with it!) and we start from there. Once the new Holley double pumper and single plane intake is installed there is a startling change in character for the engine, it suddenly pulls much harder through the rpm range and MPH at the end of the quarter goes up...way up usually. Most people can't believe a dual plane can hold back an engine like that.

Of course there are many that will disagree with me and technology changes from day to day, those RPM manifolds are basically single plane intakes with a center divider but everyone calls them dual planes..go figure? I guess the raised runner is what makes it a dual plane I guess?

The main thing is if you are building the engine with a race style cam then do the same to the rest of the engine, you won't be disappointed. Remember the whole is only as strong as it's component parts, design it as a package and forget the little dyno programs..they are a waste of time if you ask me because they don't show up dips in the power curve due to component mismatch like you would see on a real dyno, resonance in the intake and exhaust system is impossible to predict and a desktop dyno knows nothing about resonance in a port.

My two cents. :p
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Old 01-04-2003, 03:45 PM
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Great posts, Guys. 4 JC, worth much more than 2 cents.

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Old 01-04-2003, 03:49 PM
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Man chuck, that's like 35 cents. My fingers hurt just thinking about that much typing. Keep it up you'll be giving HK a run for the money.
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Old 01-04-2003, 04:16 PM
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I think 4-Jaw hit on an important point in his post, and that is the improved torque output of a dual-plane. I have built alot of really strong street engines with single-plane "race only" manifolds as they call them, and never had any low end torque problems. Probably one of the best ones was a 340 Chrysler in a 68 Cuda. This engine was a hodge-podge of parts , and it had an Edelbrock Torker single plane with a big, 800 CFM thermoquad,280 Mag comp cam, only 8.5:1 compression,ported heads, stock converter and 3.23 gears, and it had the stock exhaust manifolds to boot. Now, that sounds like a really crappy combination, doesn't it? If someone told you to build one like this, you'd probably say it wouldn't idle in gear, and stumble and spit when you take off, and probably wouldn't pull the hat off of your head.
Just the opposite was true about it's driveability, and I think I owed alot of that to the very small primaries of the Thermoquad carburetor, even with the open plenum manifold, the very small primaries and good booster venturies of the carb allowed good fuel dispertion at low engine speeds, and the thing was really tractable, and really cooked when you put it to the wood.
I THINK IT IS PARAMOUNT TO MATCH, AND TUNE YOUR CARBURETOR TO YOUR MANIFOLD AND CAM. YOU NEED PROPER BOOSTER SIGNAL FOR DECENT LOW END PERFORMANCE. THAT'S HOW YOU CAN RUN A RACE TYPE MANIFOLD ON THE STREET.
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Old 01-04-2003, 08:18 PM
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I like the old torker 1 or TM1 edelbrocks for the street. I had one on a 400sb chevy with a 750 Vaccum Secondary Holley. It had the most crisp throttle response of anything I have run to date. Those old manifolds are hard to find though and they are usually used up. I made the mistake of trading mine for a Holley strip dominator and double pumper after I went to an automatic with 3500 stall. I wish I had the old combo back. It was just better on the street.

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Old 01-04-2003, 10:48 PM
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Now we are talkin'. I say give me my 9000 rpm small block,he. Other than the rpm and gap dual plane intake should all be melted down for cans to hold more brew. .
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Old 01-04-2003, 11:02 PM
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Okay so to flatten out the touque curve I've gotta give a single plane more gas...

How well do single planes work on the street if you have a decent engine... will duel or single plane be a better choice for a daily driver with 350 to 400 HP?
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Old 01-05-2003, 12:04 AM
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Hey stoned, You are really in an area where the question is which manifold do you prefer! Just don't put a Victor intake and a Holley Dominator on a stock 305. If you want to turn some r's, go with the single plane (and a healthy cam, exhaust, etc.) if you want burnouts and chirpy gear changes with a little better mileage, go with a dual plane. And after you decide on the intake, here's an easy way to decide on the carb. A healthy engine should handle 2cfm per cu.in.. So a 350 should work well with a 700cfm carb. If the engine is Super Stout step up to a 750, a little on the mild side, drop back to a 650.
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Old 01-05-2003, 12:13 AM
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^^^^^^^ this is the type of feedback i was looking for^^^^^^


what 4 bbl carb and manifold... specifically edelbrock would go good with a stock 305.....
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Old 01-05-2003, 12:29 AM
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Hey raider, If you have a bone stock 305. I would go with an Edelbrock performer (dual plane) and a Edelbrock 600 carb. If you are ever in cold weather, the electric choke version is worth the extra $
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Old 01-05-2003, 01:44 AM
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wow, there are smart people on this forum.that explained soooo much for me and i wasnt the one asking a question. i heart cars.
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Old 01-05-2003, 06:35 AM
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See there is the thing... I would like to have something that kinda flattens out the tourque curve and hp curve so I can do nice burnouts and stuff (hey I'm 17 and this is mainly a street machine) I also want to have a bit of high end for when I do take it to the strip for 20 bucks on a weekend...

Would as chuck put it a B@stardized single plane (ie duel plane with the small gap between) work best
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