JMF Intake Test

By Uncle D | July 13, 2017 | 0 Comments


in the never-ending pursuit of performance knowledge


When Jim McKeone at JM Fabrications approached me to flow test his new intake manifold designs, I obliged. Sure! Sounds like fun. Let’s hit it. So out comes the beer and dancing girls for some after-hours weekend flow-tastic fun. A nice break from the usual order of business.

Did these proto intakes need changes? Sure they did…as with anything else that is fabricated for performance, function, and/or efficiency. Actually only a few design changes were needed on those 3D printed orange monsters. There was a touch of turbulence going on in both pieces, but once that was nailed with some creative CAD (Yay!) and Jimbo was happy with the overall flow and balance of his creations, this page was created for your review and enjoyment.

I’m also very sure that Jim will soon be out replacing all that 3D filament he used in order to have us conduct these tests. There was more plastic used in those protos than what’s currently in Mickey Rourke’s face.

Actually, to be fair, this intake test page shouldn’t have the word “Shootout” anywhere in it…as this test was conducted more to see balance and evaluate air turbulence within an intake’s runners and plenum. This test was not conducted to determine a "winner" by mere flow numbers. The second we start focusing on “Max CFM”, that will invariably manipulate folks into thinking that one particular piece is better than one with less flow. That’s not playing fair. Not the direction we wanted to go with this.

Now that you understand the premise, let's move forth.


Yes…it is. Let’s not get hung up on Max CFM numbers here. Max CFM is just one variable in a big equation to arrive at a component’s power potential. Much like in our cylinder head development program throughout the years, we have found you can have numerous ports all flow exactly the same…but they all will vary greatly in RPM ranges, power, and acceleration. That is why if you see a race head advertised with us, it will not have its Max CFM listed. It’s really erroneous data that won’t make a hill of beans to the end user (other than forum bragging rights). You should never only consider Max CFM to evaluate a head (or intake) design. You evaulate it by what the clock says at the finish line.

ANYTHING is going to move air if it has ginormous holes in it. You just make it all big, slap it on, and go. So it’s important to note, in this test, that we’re really looking for “balance” within each intake…how much CFM each runner of the intake is going to be gulped in by that cylinder of the engine.

Flow benches are great tools to use (as with dynamometers as well) but they are not the be-all end-all of performance hunters. Although they give great insight into the power potential of a performance component, engine, or vehicle, they don’t guarantee that it will give you low ETs at the track. Let’s face it…when was the last time you staged against a flow bench? Real world folks. THAT’S really what it’s all about.


By no means was this test optimally done. Ultimately, it would have been best to couple these intakes with a head...start doing the math and spend hours upon hours developing an intake and head combination that would perform fantastic with each other as a whole. So that said…

Because of time (or lack of), these intake tests lack the thermodynamics, aerodynamic, math, and physics that is usually associated with cylinder head/intake development (meaning no propeller-head data). We will only capture: Max CFM, Avg CFM, and Hi-Lo Deviation.

Elaborating on the term “Hi-Lo Deviation”, this is basically (in percentages) the difference of the highest flowing port to the lowest flowing port. The lower the deviation number, the better the overall balance on that particular intake.

With every design change done, I tested ALL intakes again at one pop (for consistency and accuracy...and simply because I suffer from OCD).


Why did I use a stock intake and a (now defunct) BJCHS intake along with JMF’s test subjects? For fun. What I had sitting easily accessible on the shelf. For comparative purposes. Because they were there. For education. For you. Take your pick. But mostly for fun.


All intakes were tested on a Superflow SF-600 at 28” using FlowPro Data Acquisition software with Flow Control. Temps were approx. 62 degrees with a Baro of 29.95. The intake test plate used was a specially designed 6061 piece that matches the intake port of a 1G head. The test plate port then “morphs” out to match a 3.386” orifice-ed fixture that is bolted directly to the bench. All vacuum ports in each test subject were plugged as well as any other through hole that might be present (other than the TB inlet of course).

That’s it. Very simple methodology for these particular test subjects. That’s what made these tests so much fun. No brain hemorrhaging evident by end of day. No pissed off wife. No kicking of the cats. But nonetheless, very potent data to have under your belt that will help you in your performance journey somewhere down the line. Knowledge is power. It’s all good.


Do I have them on this intake test? Yep. Will I give them? Nope. Why? Am I a secretive, yet arrogant bastard? Sometimes…but I feel that my personal thoughts on the test would dilute the reasons why I published the results of these pieces in the first place. First and foremost, I wanted to deliver simple data for you guys to draw your own conclusions. If I tossed out my opinions and what I think “is best” it would most likely skew the test…maybe even come across as a sales pitch. Aside of course from standing right at the bench checking and listening for runner turbulence, the data you see here is exactly what I saw. Use that noggin. Link to it. Have an intellectual conversation about it. Start an uprising in a forum. Whatever.

But really folks, within the scope of these test subjects, there is no absolute, take it the bank “winner”. They are all miles apart in differences and purpose. They all have their specific roles and can perform very well when matched to the right system of components. Hopefully this data will help you make an educated decision on which style of intake to use for a particular project. I myself have also added a new brain wrinkle or three conducting this test...which is always a good thing.

A bonus is that it has helped Jim up the ante of his own intake designs for their specific application. And that’s good for everyone. As we say here, always improving.


So without further ado, we present to you these five different intakes…five very different intakes for your review.

So grab a beer, sit back, relax, and enjoy! We hope you dig it as much as we did conducting it. Many thanks go out to Jim M. for allowing me to be a part of his design process!

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