single plane intake vs. dual plane
 

Why does everyone say if your building a BOAT motor that will not exceed 5100 rpm you need to use a dual plane intake? However, if you look at Mercuiser they use a single plane intake on all their carbed blue motors that do not exceed 5000 rpm. I don't want to buy an intake that I will need to replace later down the road because of intake limitations, plus you can buy a single plane manifold for half the price of a good high rise dual plane. Anyone have any thoughts???

General consensus is the dual plane creates more torque down in the lower revs thereby making your engine work a little better down in the cruise ranges of 3-3500k rpm. by 5k is a wash, and single plane will go to 7k.
It is odd though what goes into factory engines. Mine started life as 375 hp Innovations. They were single plane intake, large square port heads (which arguably aren't suppose to work below 5k rpm) Seemed ok. Followed a Lingenfelter build program and used large oval port head (049) and dual plane intake and made over 500hp with 107% VE.

http://www.youtube.com/watch?v=1_5TnlX-Ams Here is a very informative video on intake manifolds and the process in which they work.
http://www.youtube.com/watch?v=1_5TnlX-Ams

Life is different now.

500+cid's are the norm.

High flow cyl heads are the norm

High lift camshafts are the norm.

That's why you see way more single plane intakes nowadays on 'lower' rpm motors than you used to. Simply, because that's what the engines want.

If your building a motor like the old days, then the single plane vs dual plane laws (based on rpm) from the old days still apply.

So my next question is if I get the single plane intake like the Victor Jr. will I kill my overall performance (fresh 365 mag motors, square port heads, 280 adv. cam, built 750 marine carbs, stock exhaust manifolds with stainless risers)? I like to cruise my boat at 3800-4100 rpm (the boat just seems to run very smooth there) it will pull up to 5100 rpm max. I do plan on buying full headers and better heads down the road and later buying a full race prepped short block such as high compression internals and more of a higher rpm motor. I do not want to sell my boat, I love the older Fountains and I want to just keep increasing the performance that I already have but not ditch everything every time I upgrade.

The single plane wont do a lot for you now. You're probably better off saving them for when you wanna get a more serious set of engines.

Realistically, there isnt much need for a whole new "Race prepped" shortblock. You have a good foundation to build onto. A set of modern cylinder heads with a smaller combustion chamber will get your compression up using your stock bottom end. The right cam, intake, exhaust, you can make around 550-575hp fairly easily, and get your Fountain into the 80mph range.

In that application, I would go with a dual plane. If you get some heads with better ports (higher velocity), then the single plane will would work better. The dual plane will bandaid the weaker port of the stock head and not give up too much if any to the single plane. my 02

Sorry but after designing heads and intakes blocks you naame it on an engine porting heads and intakes for 45 some years cant go along with a lot of whats in your video couldnt watch it all.
When you got into the part about using a dual plane for a SEFI each of those runners is going to flow a different amouunt of air. I have flow tested quite a few intakes bolted to heads. oNE ENDS UP NEEDING TO BE ABLE TO ADJUST EACH CYLINDERS fuel according to runner flow as each will fill the cylinder a different amount. Been there done that years ago but used a system that I could adjust each cylinders fuel.

I've talked to the techs at Edelbrock and they say once you get much over 500ci in a performance application than the single plane is the way to go.

But it's on the internet??? (my brain broke about 15 minutes in)

I reread the OP and realized he didn't mention what combo he currently has. My comments were under the assumption of a factory mag category motor.

After examining multiple 496/502/509/540 CID trend lines, (TQ/HP curves vs. absolute output) a pattern emerged regarding the single vs. dual plane combinations. The D/P is a fine manifold for certain applications (particularly OEM or aftermarket replacement heads), however, the better the head flows, the greater the restriction the D/P poses, as the flow numbers below illustrate. With a dual plane and lesser flowing heads, valve lifts ± .550”, the power curve would decay acceptably @ or near 5000 RPM. However, at the same displacement ranges, with good flowing aftermarket heads, optimized lobes, and valve lifts > .600”, output noses over significantly > 4800RPM with the dual plane.

The test data below is provided by Tony Mamo of AFR. Both manifolds are Edelbrock, mounted on the AFR 305 CNC chamber BBC head. Keep in mind as RPM and/or displacement increases the flow drop becomes increasingly significant. The goal was to determine which manifold had the proper plenum design, runner length, and CSA to support the upgrades to the package.

AFR 305 CNC Chamber w/ Radius Plate
Intake….AFR
.200”-----163
.300”-----241
.400”-----300
.500”-----344
.600”-----367
.700”-----368

AFR 305 CNC Chamber w/Performer RPM Manifold

Intake
.200”----158--- (-5)
.300”----224--- (-17)
.400”----272--- (-28)
.500”----305--- (-39)
.600”----324--- (-43)
.700”----327--- (-41)

AFR 305 CNC Chamber w/Victor Jr. Manifold

Intake
.200”----160---- (-3)
.300”----230---- (-11)
.400”----286---- (-14)
.500”----324---- (-20)
.600”----346---- (-21)
.700”----337---- (-31)

As the numbers indicate, the % restriction throughout the flow curve, are nearly double that of the Vic Jr. using the dual plane. An intake that killed off 43 CFM @ .600” lift would seem to be well outside the design parameters necessary to achieve optimum power. It would compound the issue that you have the 315 CNC heads that flow ± 20 CFM more than the test heads.

When building an engine package that is generating 600 lb./ft. early on in the curve, it is not optimal to attempt to pick up ~10 lb/ft early in an area that is rarely utilized at the expense of 15-20 HP at max WOT. Much of the press addressing the perceived “advantages” of a dual plane are targeted toward an OEM headed, stoplight to stoplight, scenario.

The Victor Jr. /Holley 950/1000 HP is the best combination I have seen for the AFR 305 CNC chamber/315 Full port, 489/496/502/509 CID marine packages to date.



Bob

Bob, you are very much appreciated for your great input and tutelage, we are being schooled by a master.

Very interesting it is mass vs velocity at a certain point sheer mass preform's more efficiently than velocity. Do I have that right??? I was always under the impression velocity won the day...I guess without mass who care's.

The two are always important. However, getting fixated on one at the cost of the other, won't help.
There's more to velocity than just carb size, intake runner length, and cyl head runner size.

More importantly, it is results. Not just on the dyno, but more importantly on the track, and on the water. These results are what prompted all this to begin with.

Remember, that 502 with AFR's, modern high lift , higher intensity HR camshaft is going to move a ton more air and subsequently a lot faster thru a Vic Jr than a 454 with old smaller intensity Hyd flat tappet cam, OEM rectangular port heads, and the same Vic Jr.

Now, build a 540-555 with AFR's, modern higher intensity hr cam or decent but reliable SR, and guess what ? Bring on the Vic 454R Dominator intake or equivalent, and go even faster. Still sub 6k motors.

We are in some very good years of hp building and it's only going to get better.

As I've quoted a billion times from Darin Morgan " Your motor is telling you what it wants. Are you listening ?"

thank you for everyones input there are definitely some very knowledgeable people here. I am going to go ahead and go with the single plane victor jr. And hopefully mid to late summer I am going to purchase aftermarket heads. short block on my engines are darn near bulletproof and very reliable, so Im sticking with The 454's for now! I think a bulletproof bottom end and an all new aluminum upper half will be just fine for what I need. thanks for the help!!!!

bore notching it wouldnt hurt either

With no other changes what impact would a dual plane intake have on a 502 mag

Are you oval or rectangle port? I think I have an oval port Vic Jr laying around that I'm not going to use.

Huh, learn something new every day. Might be time to look for a new intake manifold.

Which 502 Mag ?

Reason for asking - the carbed version's have a high rise GM intake. The MPI's have fuel injection, and yes, if you convert to carb with Holley 800 or so and a good aftermarket high dual plane you will gain power. With it's dinky lame azz cam, a HR dual plane with work well.

mark 5 carbed version, embarrassed to say I have no idea what intake is on it or what cam is in it

I always enjoy seeing an engine combination, with a dyno sheet. Esp a 540 with AFR 315 heads. :santa:

If anyone is interested and can post it I can send you the dyno graph of my carbed 540 with 315 AFRs and vic Jr.

Don't forget about the tunnel ram guys. The old myths about them have been smashed time and time again and a properly tuned tunnel ram will increase the air flow of the cylinder head...

The only time I have flowed an intake and recored a increase in the flow of a cylinder head is with a realy well designed sheet metal intake, most still loose a bit. A well ported cast intake of any type or out of the box drops aiir flow through the head.

And your point is?

thats for sure,especially for larger intake vales like 2.19 or 2.25"

That an intake that can flow more wont increase air flow of a cylinder head unless the cylinder head already has the ability to flow more air.

No it does I've seen it done on a flow bench. It's been a couple years since I've seen it and honestly at that time I really wasn't interested in it @ .500+ lift the head started gaining with the tunnel ram on it not much but it started gaining. I kinda dismissed what I witnessed on my buddies bench until about a year ago. I started looking into tunnel rams. I called all kinds of cylinder head guys alot of them said yes if done right the will pick up some said no they will not. They are called a tunnel ram for a reason...

Posting it up for you bud.

660HP from a mild 540, at 5600RPM, is excellent numbers. The torque curve and peak point, is also excellent. Very nice combo. My guess is it has a very mild camshaft in it

I have to ask though, was this particular pull, where the engine made its best numbers? If the AFR data is correct, my gut tells me you may have been leaving a little power on the table being that lean.

On big block's and based on some of the input single plane seems to be a obvious choice on small block's id be hard pressed to agree with that. Actually could it be due to lack of proper intake design for high HP big block's? Even on small block's there increasing the plenum size to accomidate higher power aka more mass or air. The vid's a bit corny but it does address the issue.

http://www.youtube.com/watch?v=i2DvnoHWagk&feature=player_detailpage

I think your on to something!
I think Mild said it best when he suggested a better set of heads, just the intake is not going to do much!

I'll tell you my thought about that A/F ratio.

I'll bet a $100 the A/F ratio was derived from the airflow meters #'s vs the Fuel Flow Meter #'s. Not a wideband.

If that was a wideband, why was the engine not tuned while on the dyno ?

It is not a super accurate # and no real info can be attained from it. Not uncommon to be a point higher than what they should be.

In me experience the fuel flow meters are more accurate than the airflow meters. I look at both #'s seperate for other things but never together for a/f ratio.

Those were the best numbers and I've been told by someone else that it's dangerously lean. Your thoughts? Also, that run is with the addition of a 2 inch spacer which made a big improvement across the board. So single planes don't necessarily hurt mid range. Just sent you a pic of the chart prior to the adding the spacer.