MakoShark72

All things being equal, is there an accepted "number" of what a dual plane intake costs in terms of HP? I have read that the single plane manifold adds HP in the mid and high ranges, and the dual plane intake is better for low end torque and "driveability"....

Getting my new 383-500 motor back tomorrow http://www.sallee-chevrolet.com/Chev...8s/383-500.cfm, and "advertised" numbers are 500HP/491TQ with single plane Victor Jr manifold.

I am using a dual plane Air Gap manifold, and my builder's desktop dyno came in at around 485HP/515TQ. BTW, the TQ curve is above 500 from around 2000 all the way thru 4000 rpm's.

I have heard the dual plane costs up to 20 HP or so...again in mid/high ranges.

Thanks!! Pictures of the motor in the next couple of days.

cv67

On that motor take your pick it will make great torque if you use a dual plane or single. Probably lose something over 5000rpm or so with the DP.
Can always switch up if you like.

IMO you dont need a DP intake to build torque, its already there with that one.

billla

As always, it's about matching the overall combo of parts - not just one piece.

Generally, if the heads are flowing past about 260 cfm or so, or if the engine is making more than about 1.2 HP/CID - it's time for a single-plane to maximize power.

With that engine making over 1.2 HP/CID and the AFR 195's...I would use a single-plane intake.

427Hotrod

Depends on the motor, the intakes and the rpm range.

I did a 400" this year for some articles in Auto Enthusiast and it's in Devildog's '61 over in the C2 section.

It made 540 HP@6100 rpm with the Dart *air gap style* dual plane and 555 HP@6300 rpm with a Team G single plane. Tq actually peaked higher with the single plane at 520 lb ft for the single vs 513 lb ft for the dual plane. Both peaked TQ at 5100 RPM. Down at 3000 rpm the dual plane was making 480 lb ft vs the single plane making 462 lb ft. The single plane passed the dual plane at 4800 rpm and at 6500 rpm was still making 550 HP. The single plane was *hanging on* fantastic where as the dual plane was down 30+ HP by then.

So it all depends on RPM range. I like the single plane's ability to deliver when you really get with it and still able to do really well down low also. If your cam and heads are done by 5500 rpm..then the dual plane is definitely the winner if it's a good one.

JIM

OzzyTom

I considered the same change, but then I heard the dual plane airgap does not compromise any significant power up to 6000 rpm.
It does provide slight gains in lower rpm torque though, which is appreciated in sedentary driving.
The single plane will provide some gains past 6000, but will tax some lower rpm torque.
Not sure how much though. Might not be noticeable depending on your gearing.

What are the engine specs of your motor..... 500 horses in a 383 require a reasonably big cam so bottom end torque may be compromised somewhat.
Gearing will eliminate driveability issues with whatever intake you use.

I have a 383-475hp spec crate engine with the Edelbrock airgap manifold and am happy with its performance now.
The original 3.36 diff gears was causing concern with driveability, but now with 3.7's it is working perfectly for my driving requirements.
It will pull away from just off idle in 4th gear without complaint, but motor doesn't really get going till above 2500 rpm.

From 3000 to 6000 it is simply sensational!

My personal thoughts are that you will more likely notice a drop in lower rpm torque than you will any slight gain in top end power.
It really will depend on the whole package and what your objective driving style is.

edited... just noticed the link to the engine specs.
Looks good. Those flywheel numbers look very strong.

Go the single plane and see how it runs.
What diff gearing are you running?

MakoShark72

Thanks guys,

My build is pretty much what is posted on the Sallee website http://www.sallee-chevrolet.com/Chev...8s/383-500.cfm , since the foundation is a GMPP ZZ383, except..

My cam is a Chris Straub custom grind Bullet.. 230*/236* duration with lift of .540"/.521"

Rockers are 1.6 Scorpions (instead of the 1.5 GMPP)

Edelbrock Performer RPM Air Gap manifold (instead of the Victor Jr)..FWIW, my engine builder recommended the dual plane for "driveability" seeing as I already had it!

2004R trans w/ 2400 stall converter

3.08 gears

I would characterize my driving style as "fun" street driving, low and midrange, no racing or drag (at least not on a track!), no extended high rpm's (say above 5700)

Sounds like any way we look at it, I will notice the difference from my ZZ4?? Reason for the original question, is we were a little surprised at the sub-500 HP number from the desktop dyno, until we realized that Sallee used a single plane intake, and they (Sallee) mentioned that a dual plane COULD cost up to 20 HP... if thats the case, my motor would be at 500 or a little over...

Thanks!

tekvette

I would choose the dual plane based on your trans, converter and gears as well as your intended usage for the car.
Your side pipes should give you a good amount of low end torque as well because of the long primaries.
I wouldn't worry too much about the sub 500hp #. I think she will have plenty of grunt down low and she'll be a blast to drive.

MakoShark72

Tekvette,

Thanks, and to be honest the HP number doesnt concern me at all, I was just wondering about how the intake itself, affects overall performance, as I said, all else being equal...

Glensgages

I have a fairly generic 355" SBC in my '79 Z28 (unported iron Dart heads, 292H cam, 10:1 squeeze, etc), and have run both a Victor Jr., and a dual-plane aluminum intake from a 327/365 Corvette, under the same 750 Holley DP with open-headers:
rest of drivetrain is 8" converter, low-gear'd THM400, 4.11's & 28" slicks

car runs 12.90's / 12.80's @ 105 MPH, regardless of which intake is used, (almost) regardless of the atmospheric conditions:
car runs quickest when shifted at 5800 RPM, and the similarity in performance no-matter which intake is used might-be due to the low shift-point, loose converter & gearing

???

cv67

A 3.07 gear with that cam maybe a good dual plane is for you.
There is no cut and dry rule on intakes it all depends on the combo/car/gearing/usage.
Yes a 383 will swallow a little cam and head but they also move considerably more air wanting more than the 350 would at the same rpm.
In any event changing an intake is an afternoons job at worst..if you stop for beer breaks.

MotorHead

Once again instead of listening to old wives tales I compared a Vic Jr to RPM Air Gap on the same motor. The motor was a 400HP or so 350ci and the Vic Jr made more HP and it made more TQ another misleading "fact" that never seems to go away.

I believe what fools people is that if you have some crappy smogmobile the Tq is going to be higher than the HP. Once you get a properly set up motor you should be making more HP and that is just what it is, more power, your HP doesn't go up and you Tq goes down, just the opposite your HP goes up and your Tq goes up, how can it not you are making more power.

Sometimes things get ingrained into people that it takes years before the overall opinion changes. This was my 355ci I had in my Vette 10 years ago and I purposely put on all the parts everyone at the time said wouldn't work on the street. The car ran great on the street even with the 3.08 rear end.

I put on a Holley 750 DP mechanical secondaries, Vic Jr single plane, solid lifter cam etc. Now it seems these parts are being more widely acceptable and more the norm than not.

RPM Air Gap


Vic Jr

69 Chevy

You could always cut down the center divider on that dual plane manifold to make it act more like a pseudo single plane.

MotorHead

Yes the Air Gap has a cut down divider but it is also IMHO the best dual plane out there. I can guarantee no other dual plane will come as close to the Vic Jr at higher RPM's. Once you get up over 5500RPM the Vic Jr starts to really shine and pulls away from any dual plane.

The point of my post is the fact that the single plane Vic Jr isn't "losing" any torque, it is actually gaining in torque over the dual plane because like I said above it is making more power period.

Shark Racer

Interesting - are the two dyno graphs just with an intake swap? I wish the air gap dyno started lower, but even so, at 3k the Vic JR is making more torque, and even at 2200 it's making more than enough to fry tire.

billla

It's all about the components. Put a single-plane on an otherwise stock engine and clearly you lose bottom end torque...put one on a serious engine and there's loss of a little low- and mid-range throttle response...but not much if any loss of torque. Those types of engines usually don't spend much if any time below 3K anyway

The Vic Jr is one of the best single-planes out there, bar none.

billla

That tends to extend the RPM range to some extent - about 500 RPM - but a single plane will still outperform the dual-plane in this application.

gkull

The correct answer is:

Find out the head port size and you have to get an intake that closely matches.

If you have some small block 300 cfm heads requiring a 1206 FelPro intake gasket. So the head port is 1.34 X 2.21 inches and you like a dumb *** think you are going to get more TQ with a Performer dual plane with 1.22 X 1.86 inches outlet port size. You are screwed. Fuel separation loss of intake velocity................................

A correctly tuned intake track makes additional power

Just use the correct matching components.

3.08 and a OD tranny is another miss match. a 383 if it really is making 500 hp is not going to have a bunch of lower rpm TQ. You will be way over geared in 4th. Desk top dyno is a tool. You will not have 500 foot pound at 2000 rpm. Very few hot rods can even take on full throttle at 2000 rpm on a fully loaded dyno. I'm a dyno operator.

Solid LT1

Funny how the Victor jr pull was from around 2600RPM and the Air-Gap pull was from around 2000RPM in my expiriences, single plane makes top.end HP at the sacrifice of bottom end torque. Yes the numbers are there but when you take facts in like drivability and transmission type there are more factors to take into consideration when picking an intake. If the Vette has an auto trans, NO BRAINER, air-gap.

MakoShark72

Thanks everybody (I think).

Good discussion on this topic! I think I'll stick with my Air Gap, since its already on the motor. Can change it if I feel the need.

gkull

Hey I didn't say that you were a dumb ***. Because I have no idea what size your head ports are or even your specific intake. I was refering to people who have big heads and tiny dual planes and think that they will achive some magical low end tq. or little heads and a super big single plane

I do stand by the bogus desk top dyno 500 foot pounds at 2000 rpm figure. You can't apply 500 foot pound of resistance to a little 383 motor at 2000 rpm on a dyno. It would stop the motor. Look at Motor Heads dyno sheets. You have to do a few practise runs on each motor and get a feel for when it can start going (rpm) to take full throttle and where to start on the initial load and how fast you can bring in full load.

So look at his run #2 dyno guy started the test at something just over 2600 rpm and it ran fine. Then over a 40 days later and the intake change he was running the throttle on #4 and loading the motor to a balance of about 260 some foot pounds started the recorder, WOT, and fed in a higher load factor when the rpm came up

See the TQ wiggle at the start of 4 on the tq? The motor hesitated going to wot under only 260 foot pounds of load and low 2000 rpm. Going from 355 to 383 is worth about something less than 40 foot pounds.

You floor your 383 next week when you get it running and the TC will flash to something over 2400 rpm anyway and it will bring a smile to your face even if it didn't have what DD said anyway