Box type upper intake manifold help

Bigger is not always better. In a NA application, port velocity is important...especially for low-end/mid-range power.

That being said, I'm not suggesting a small runner intake designed for a 302. A good choice would be the Edelbrock Vic Jr. 351 intake. A true long runner would be the 351 versions from TFS.

And that is the only response you will ever find.... "Port Velocity is important"

My take on it is...
There is more to it than just 'velocity'
The cam, head, intake *size* (for lack of a better word) need to be matched to the displacement and intended rpm usage.

Replacing only ONE of these components creates a mismatch in the parts, making it an unfair comparison.

just my take on it though...

best of luck guys,
jason

Agreed. The application is the key to the combo, but the owner hasn't replied stating the intended usage.

However, it's also unfair to say that there are no alternatives to the box upper due to port volume. The long runner intakes I'm suggesting have larger port volume specifically designed to feed stroked Windsors, and the longer runners to provide good velocity at lower RPM's. I guarantee a setup like this will provide more torque.

I'm not talking about a Lightning lower either.

Originally Posted by vristang

On the 408w... no.

There was no way I was going to choke the motor any more than I already was with a Lightning lower intake.



I see the same 'long/small runners make more torque' argument being pushed here.

Let me ask a more general/basic question...
"How does a restriction in the intake create more output?"

"By masking problems elsewhere"......... I've worked on two 302's with Cartech "coffin" boxes, the first one was N/A and the other was SC, but neither lost torque down low.

Prove it.

I want to see dyno numbers of a fair before and after comparison showing "no loss in torque down low".

Everything I've ever seen says otherwise. The loss of torque on a street application is usually "masked" by gearing the crap out of it.

By fair, I'm suggesting an aggressive application with a box upper vs. an aggressive long runner such as the Edelbrock Victor. On a NA 302, I'll take a Holley SysteMax over a boxed upper any day.

Originally Posted by 87stang

Prove it.

I want to see dyno numbers of a fair before and after comparison showing "no loss in torque down low".

Everything I've ever seen says otherwise. The loss of torque on a street application is usually "masked" by gearing the crap out of it.

By fair, I'm suggesting an aggressive application with a box upper vs. an aggressive long runner such as the Edelbrock Victor. On a NA 302, I'll take a Holley SysteMax over a boxed upper any day.

I don't have dyno graphs to bring out... sorry.

Maybe we can discuss this though, and make a little progress.

Joel has provided examples that he had first hand experience with, so have I...
Do you have specific examples you can provide to aid the discussion?
(not being a smart ass with the question... just asking)


The challenge is going to be in the 'fair comparison' aspect.
If the intake runner length/diameter change, then so should the cam events.

Another thing to ponder...
What creates the velocity that you care so much about at low speeds?

First off, I'm not into this for the argument. I consider it an excellent discussion, so thanks for keeping it civil.

Second, Ford didn't just "band-aid" their 5.0 intake design. Some serious engineering went into the design, and I'll argue that they did a great job.

Joel really did not get very detailed with his examples, but there is lots of info available:

Long Runner Comparison articles (valid in showing power losses below 5000 rpm in aggressive long runner intakes):

TMoss Porting > Tech Articles > Street Engine Intake Ramblings
Super Intake Shootout - Muscle Mustangs and Fast Fords


Long Runner vs. Box Upper:

AFM - Flow at Last

Probably the best example for the application we're looking at.


AFM - The Runner Volumes

I know this is not the best example, as it is a small displacement/small cammed engine, but it is supercharged and not only turns decent RPM's, but makes decent power. Therefore it is a good example of decent power being made on mild parts. The most noticeable point is that: "no box outperformed the short-runner intakes in average or peak power production."


My whole point is: the intake plays a huge role in the powerband of an engine. While a boxed upper may outperform a long-runner style intake at high RPM's (well above 5000), it will not do so below that point. Realistically, most of us will not build a motor for a street vihicle that will turn more than 6,500 rpm regularly...especially a large journaled 351W. Therefore, a long-runner intake will make more average power under the curve.

Now, if you needed to soften up the torque, due to traction issues and such, this is one way to do it. this is a really old article, but they make some great points towards this part of our subject:

AFM - Manifold Destiny


Port Velocity has to do with air being pulled through the intake by the piston as it moves in the cylinder and creates a vacuum. Air being pulled through a smaller port (into the same sized cylinder) will gain more velocity (speed) as it travels to the cylinder than a larger/shorter port will. What matters, in the case of low-rpm velocity, is what happens as the intake valve closes. Each time the intake closes, there is a rebound effect in the air flow. A longer port will "cushion" this rebound more at the lower rpm levels...resulting in better airflow into the cylinder, and thus more power.

Here's more science into it: Head Porting Principals

Edit: Double Post...

Edit: triple post!!

Originally Posted by 87stang

First off, I'm not into this for the argument. I consider it an excellent discussion, so thanks for keeping it civil.

Second, Ford didn't just "band-aid" their 5.0 intake design. Some serious engineering went into the design, and I'll argue that they did a great job.

No one said Ford designed a band-aid intake. Keep in mind that Ford, as any other OEM manufacturer, has to comply with the emissions requirements for the year + taking in consideration the whole setup, they made it work.

Now.... regarding the linked evaluations and conclusions ..... they don't pass a validation test....... ..... why?...... simple, it's an evaluation exercise predisposed to failure of some of the intakes (box included).... why?...... imagine setting an efficiency evaluation of the operation of a 4 controls panel by a one handed person, a normal two handed person and a centipede........don't you think the results would be academic? Same thing happens when any component is evaluated using a baseline, the results will be skewed towards the side the baseline was set under. In other words, they are not representative of the overall capabilities of the component under evaluation.

Take a good look at the linked evaluations and results.... lets use AFM - The Runner Volumes as an example....

What if:

1. Boost level was varied/optimized for each type of intake?
2. Camshaft events were optimized for SC conditions + heads utilized?
3. Valve train was also optimized based on the "total combination" of components, intake types inclusive?
4. TB size used/intake style was also optimized?
5. Exhaust is modified?
6. Different heads are used per intake type? ..... among other "variables".

See the trend?......... a better "conclusion" for that evaluation would be....."based on a similar setup as the "test mule engine" used, long runner intakes perform better on a dyno."...... but you cannot use those results as a generalized conclusion applicable to all the combinations possible of all the other variables left as constants....... that, is bad engineering...... IMHO and experience that is.