Composite mpfi manifold

69stang_250

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Hey guys,

I was doing some research over the past few weeks and I have been thinking about how much more power could be had by a composite intake manifold on the aluminum cylinder head. I was looking at the 300 inline fuel injection intake and was wondering about that design. Does that turn in the intake hinder airflow? I know longer runners tend to move torque up the power band. How long is too long? Do you guys think a mpfi composite intake designed similar to the 300 inline would make much of a power gain over the current vintage inline intake?

What do you guys think?

Worth playing around with it?
 
"...What do you guys think?
Worth playing around with it?..."
Go Ahead... I'd love 2 sit back'n benefit frm your work. LOL
:idea:
 
The Australia 250 Crossflow EFI came with a similar intake manifold to the 300.
Known as the banana intake.
 

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The plenum size and shape are the most critical part of this design, second being the runner length and shape. Keeping airspeed and equal flow to the ports is the critical part of the plenum shape, the size has to be large enough to feed the cylinders. So if the engine is 250 cubic inches, the plenum needs to be nearly that large as well to feed the engine, or it will run out of air in the upper RPM range. So for hot performance engines you need a near 1:1 ratio for plenum to engine displacement, naturally aspirated of course. Forced induction needs more plenum size, and 1.5:1 or larger works well for those apps. I have designed and currently make an EFI style intake with these parameters and it works well.

As pointed out about the Crossflow intake, it could also be close enough to fit your head with only simple to moderate modifications. So just use that one, all the engineering is already figured out.
 
A lot of Crossflow owners with EFI believe the banana intake is too restrictive for a modified 250.
However, it works well on a modified 200.

The reason is what CNC-Dude sights, plenum size and inner diameter of the runners.
 
Since the runners can be taken unbolted from the plenum, a thorough porting of the runners is a breeze and a custom plenum of a larger size can be fab'd to accomodate most any needs.
 
Not worth the hassle, you can't run a cam that comes close to finding the potential of this head due to valve length/installed height so why bother with a better flowing intake.
Walt
 
The CI data for the aluminum head shows and approx. gain of almost 50 HP by using injection over a carburetor, or 351 HP on a 250. So I think it is worth doing. A ported head will achieve an even higher gain.
 
Sorry for late response to all of these.
I can imagine there being a power gain with mpfi considering with a carb there is a lean condition to the front and rear cylinders.
I have been reading a lot on intakes and wondering just how much more performance I could get out of my set up with mpfi. The other side of it is the thought of a composite intake manifold. I am woundering if going that rout could help with heat soak. Or is this something we are stuck with since the intake is right over the exhaust?

I was thinking about trying to make something along the lines of the 250 crossflow intake or the 300 inline intake.

So my understanding is that and intake should be class to the same volume as the cu/in of an engine?
Or is there another way I should be looking at this?
 
Yes, volume of the plenum itself, not including the runners should be close to a 1:1 ratio cubic inch wise for a considerably hot performance engine. Naturally aspirated of course.
 
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