Single Plane versus dual plane

[workingdog]

I've searched back a ways and have a basic idea - but I'm still curious about the specifics.

I'm converting a Ford 390 FE to MS EFI. I currently have a Edelbrock Performer RPM dual plane on the engine and I have a victor sitting in a box that I was intending to use when I went EFI. This is a F250 truck that will mostly do towing so I need a lot of low end torque.

I had heard that dual plane is good only with carbs for getting the air/fuel mixture right before it enters the cylinder and that with EFI always go to a single plane becuase that doesn't matter any more.

I've also heard that there is no low end on the single plane because of lower velocity in the runners.

What's the skinny for this Ford big block?

Peter

[69 1/2 Six Pack Bee]

If you want to keep the grunt, keep the dual plane. The longer runners help increase the charge velocity into the cylinders plus the distribution is much better. If you want torque--go dual plane. If you want higher revs---single plane.
The 402 in my '72 Chevy is topped with an Edelbrock Performer.
My truck does nothing but pull around my 11 1/2 foot Lance camper. Put it this way---my combo with the 4-speed will pass the newer gasser rigs going up any hill and will pretty much match their MPG as well.

If you want the engine to breathe and if the components are matched commensurate with a towing engine that Victor will have no business being on top of that FE.

[Jim]

Hi , Workingdog , (I'm one of them too)

I've built many hotrods over the years and can tell you exactly why
you want to use that Victor instead of a DualPlane .

You are correct in assuming that part of a dual plane manifolds job is making a Carb work better ,
it does this by providing strong well spaced pulses of vacuum for the carbs venturis ,
you can tell this is going on by simply flipping the air cleaner lid over
and then stomping the throttle , that really loud "BaaaWoooooo" is
created by the intake manifold ,
a single plane is much quieter and smoother sounding , and no ,
it doesn't provide much of an advantage when used with Fuel Injection
except for the fact that dual planes generally have smaller runners and
are "tuned" to provide to provide a "ram air" effect at low RPM .
This can actually be a BAD THING when towing , this "tuning effect"
actually tends to make the engine much more prone to knock and
need premium gas !
This tuning tends to make the Torque Curve real fat at low RPM and start to weez at higher rpm .
All Engines are more prone to knock around their Torque Peak .
All Engines are more prone to knock under 2000 to 2500 RPM .
So , don't do anything that would put your torque peak under 2000 RPM .
This is especially critical when towing , and many people will tell you
that a towing engine has to be setup for low end torque , I say BS .
Cubic Inches and 3000 to 3500 RPM at cruise is what you need to tow ,
so an Intake manifold that is designed for this RPM range or maybe a
little higher is the way to go ,
that way when you have to drop into a lower gear to pass or just get
moving you get your torque boost in a range that is less prone to knock
and will help make more horsepower when you need it .

Also , understand that a single plane is not going to "kill" your low
RPM torque , it just won't provide a boost at low RPM .
Generally speaking , a single plane manifold usually has flatter ,
wider torque curve , which is really what you want .

Second Point ,
some dual plane manifolds have terrible mixture distribution ,
some cylinders will be leaner and some will be richer , this is never good ,
most single plane manifolds have better mixture distribution properties
than dual planes , and a throttle body is no better than a carb when it
comes to mixture distribution , the only way to completely fix it is with
individual injectors at each port .

By the way , be very careful setting up your MS BEFORE you do any towing !!!
If you start towing and are running into any knocking conditions ,
and you don't hear it and back off right away ,
you can trash you engine in a matter of minutes !!!

P.S.
Make sure you have the right rear end gears for towing ,
anything in the 2.xx to 1 range and even the low 3.xx range
is completely unaceptable , you need 3.7 or 4.11 gears ,
lower ratios (higher numbers) if you've got really tall tires .
33" to 35" tires go with 4.56 to 1 gears .
THIS IS MORE IMPORTANT THAN ANYTHING ABOUT YOUR ENGINE

[workingdog]

Great post.

I've got 3.75 gears.

So it sounds like multi port (batch or bank) would be better than throttlle body because of the better distribution - correct?

Does it change any of what you said if the long term goal with this engine is to add a centrifugal blower? I assume not, I'd simply get a hell of lot more low end torque - right?

Peter

[Jim]

Multi-Port IS technically better , BUT
How much better depends on many factors ,
It's not a night and day difference .

A Single Plane Manifold is one step towards less difference .

You will need to work a little longer to get your AE
(Acelleration Enrichment) dialed in just right .

You don't have to worry as much about your Fuel Injectors being
Exactly Flow Matched to each other which can result in
mixture distribution problems worse than any Dual Plane .

Idle Stability is probably "slightly" better with Multi-Port

BLOWER :

You will NOT get more low speed torque with a Centrifugal Blower .

Because it is not a "positive displacement" type of blower ,
the power increase will come on progressively and smoothly
and increase directly with RPM .
THIS IS GOOD and SAFE for a Tow Vehicle .

If you do ANYTHING to increase the low end torque except adding
Tri-Y Headers or more cubic inches , you will be increasing your
chances of engine damage because ultimately what you are doing
when you increase low speed torque is you are making more
pressure inside the cylinder at a time when conditions are just right
for causing the mixture to DETONATE instead of BURN SMOOTHLY ,
this can easily lead to the destruction of your engine .

From the Factory , your engine is set up to make the maximum
amount of low end torque that can safely be made with
"Regular" Pump Gas .

The only places where it is practical to increase power in a
substantial way is ABOVE 2500 to 3000 RPM .

Where you want power for towing is between 2500 and 4000 RPM ,
putting your engine under a heavy load below 1500 RPM is not practical
and only diesels can withstand it for long periods , gas engines will usually
rattle themselves to pieces (Knock/Detonation) in short order .

Future Plans ,
Blower Kits are usually adaptable to what ever you have ,
as long as you've got the room , like in a truck , you shouldn't have
much trouble installing one .
TBI or Port Injection doesn't make much difference here .

However , you would be better off buying a
500 plus cubic inch Big Block Crate Engine from Ford ,
Now that's Serious Torque , much more than you would get from
a 390 with a blower and headers .

[workingdog]

Really?

A 500 crate engine would get me more torque than the 390 with a blower? Interesting. My understanding is that I could more or less double the effective ci with a blower to about 700 ci. I could always bore out the 390 to a 428.

Peter

[eliotmansfield]

Having purchased a brand new victor junior for my SBC converting it, loosing my bottom end torque and subsequently reconverting my original dual plane manifold - The thing I learnt was that you use the same selection criteria for the manifold, regardless of how you're fuelling it.
my story is here:
www.mez.co.uk/ms8.html
 
This is in a heavy (well probably featherweight by American standards) 4x4, with a 350 sbc in it (now turbo'd)
 
Eliot.


Posted by email.

[PSIG]

Ptsha! And to think all these years I've been towing the race cars to the track with the truck - and it should have been the other way around!

Seriously, the higher RPM route is certainly good for higher power towing (and anything else where you want more power without boost), but only if the entire system is modified to accept it. This means you also need to re-cam for the higher rpm's since it's going to crap out just when you're getting the manifold to it's happy zone. There are several on this list that have been very disappointed in the performance without the several other changes required.

Don't forget your transmission. If it's an auto, your torque converter is going to strap the engine to the wheels at 1200 rpms - and you can imagine how hard it is to get a trailer moving with a midrange engine at 1200 r's. It's like towing your house with a BOSS 302 and 4.56's.

If it's a clutch, you're gonna spin it up pretty tight to get that old torque level to get things started. Of course, once it's moving, you're in good shape. Just look at the typical U-Haul. Those things are nearly at redline at the speedlimit! Of course that's with the steep rear gears, too. The downside is when you're not towing and the gas mileage keeps Exxon in business.

So, my 2¢ in answer to your original question - if you're not going to properly refit the complete drivetrain for the higher rpm's - go with the current configuration and the dual-plane. It's currently running on the engine, and if it's not already pinging itself to destruction, EFI won't make it get any worse. Once you are confident with your EFI conversion capabilities - get out your wallet and build your tow monster!

FWIW,
David

[Jim]

If you change from Dual Plane to Single Plane ,
and you are running a carb and distributor for timing ,
and you don't go through them and tweak everything
for the new setup , the engine is going to feel weak at low RPM ,
The carb doesn't like it and goes lean and develops flat spots and
bogs , the ignition timing should come in much earlier and
be bumped up 4 to 5 degrees over stock timing , and you now
need an adjustable vacuum can because it needs to be bumped up too .

WITHOUT completely re-doing your Ignition Timing Table ,
(imposible to get it ideal with just a distributor)
AND doing some extensive carb tweaking.....

YES , you will be very disappointed if you just change the manifold .

That's the beauty of Computer Controlled Fuel Injection and Timing .
Back in the day , I did it the hard way , many times ,
way more hours than I'd like to admit .

There's no easy way to have your cake and eat it too , but
computers make it much easier now .

Check this improbable combination :
'72 Camaro , 350 , 11 to 1 compression ,
310degree cam with 106degree lobe centers ,
Victor Jr. intake with a 2" spacer and a QUADRAJET carb ,
close ratio 4 speed and 4.56 gear , radial tires ,
runs 12.15s in the 1/4 mile
AND GETS 20 MPG on premium pump gas .

Or this one :
Chevy C-30 Dually, short wheel base no bed , 5th wheel hitch only ,
pulls an 11 by 40 foot furniture delivery trailer ,
Stock 454 Big Block , THM-400 Auto Trans , 2.73 rear gear .

Install Tri-Y headers with an X-Pipe into 2 Y-pipes, into 4 "Sonic Turbo"
mufflers , excellent power increase at all RPMs but especially
3 to 5000 RPM , engine runs much cooler , no more overheating problems .
Next , add Performer Dual Plane , engine runs unevenly , and now
knocks unless timing is backed off , this makes it a real dog on low-end .

Change to old school Edelbrock "Tarantula" single plane with 2"
Holley to Quadra-Jet adaptor , (still running stock Q-Jet) ,
now timing can realy be cranked-up , 16degrees static , 36 degrees
at 2000 rpm with advance weight and spring kit .
This made the engine "come alive" ,
More off the line grunt than you could imagine .
After work , with no trailer , he would entertain himself by
blowing away any Tuff Guy Hot Rod he could find .

By the way , after some more tweaking , this truck routinely got
12 MPG at 65 MPH with a fully loaded trailer , running between
Miami and Key West . This is no "tall tale" , I was there .

The Point to all this is that you can't just bolt on parts ,
there's no "easy button" you can push ,
you have to understand exactly what is going on inside .
KNOWLEDGE IS POWER

[workingdog]

I really appreciate all the comments. It's very, very educational. It's really good know that I just can't slap the Victor on without making other changes.

There's a C6 bolted to the back of the 390 right now.

Peter