That tends to be the case with a lot of people, just grinding to make them even. The fact of the matter is you can't make them consistent without a flow bench and even if you did, it wouldn't matter. For them to flow even they have to have a different port size, but size will affect pressure which dictates flow and that's a changing variable. I'll expand on it a bit below.


Be very careful with calculators like that. They assume perfect conditions (STP) as well as 100% volumetric efficiency. So in reality, to be able to apply something like this to a force inducted application you would have to know your cylinder air mass to determine your peak VE (which will be well over 150%) as well as how the air is acting at that certain pressure (because air is tricky and will do different things at different pressures). So in reality it's just about impossible to perfectly apply such a calculator, but for all intensive purposes, if you know your total airflow, they you can predict how much power your engine would make (in a perfect world).

28" is the standard for most performance stuff nowadays. My reasoning for testing at 25" is because that is what the bench was calibrated at and it's most accurate there. I could do testing at 28" but it's too late now. You can convert the numbers to a different pressure but it's not really a perfect conversion so it's best to just stick with one pressure and keep it consistent :)


I don't see it as a bandaid. Like I said, what matters is that what goes into the port is equal across cylinders. It doesn't matter how that is achieved so long as that is the end result. The problem with a tri y design like you're saying is that it still needs a plenum, it creates a fairly long path, and would not be feasible in the space we have without make some very uncomfortable bends which will hurt flow. IMO the biggest difference between the stock manifold and the JMF is the plenum volume to runner length ratio. The stock mani has a small plenum and long runners. This helps with velocity at lower RPMs and allows for a more usable powerband. On the other hand, the JMF has a huge plenum and very short runners. This means that overall power will be higher because more air can be flowed, and it has a shorter path to get to the cylinder which aids in high RPM power. There is no such thing as a perfect manifold for all cases. It's something that each person must tailor to their own needs in order to achieve best results for what they are trying to do.

Also, our stock manifold has a fundamental flaw, which I covered in the OP and touch on a bit above. And that is our throttle placement is on the side of the manifold and that means in order for air to get the cylinder 4 it must take a VERY tight 180* turn to get into the port. Air does not like to do this. And for that reason 4 will always flow the least. So you would think the solution would be to open up 4 the most to get it to flow equal to the rest. That is not the case however. By doing so, it is possible to equalize them on a flow bench but there's two problems with this. First, a flow bench does not perfectly replicate a running engine (actually it's not very great at all) but it is the closest we can really get short of using an actual engine. Airflow is something that can only be learned through trial and error, you can make predictions but the only way to really know what it's going to do is through testing (which is why flow benches were made in the first place). Second, runner volume dictates pressure (they have an inverse relationship) and pressure drives flow but flow is more than just pressure. So even though on a flow bench the runners are flowing the same (if sized differently, like I mentioned) the air will enter the cylinder head at different pressures and thus at different flow rates on a running engine. Sorry if that doesn't quite make sense, it's kind of tricky to fully grasp (at least for me) without a good image.


No. Just because you pick up more airflow does not mean you pick up more power. Power is made by burning fuel. If you have more air you must add more fuel. Without adding more fuel you will gain no more power. So, if you still have fueling headroom, then by adding more fuel you can indeed make more power :headbang:

@Mazdazilla6; I appreciate all the hard work and effort you have put into this for us all. I have a gasket matched PnP intake manifold i got from Kozmic Motorsports a few years ago. in your opinion, do you think it would be a waste of time and effort to go single runner on it? I see that there is obviously an increase in flow, but would there really be any benefit worth gaining?

If you're chasing gains to get every last ounce out of it, it wouldn't be a bad idea. But honestly, if a ported mani is REALLY holding you back on power then getting an aftermarket one would be a better solution. If I were in your shoes I would leave it as is.

I don't think it's holding me back as my car flows pretty well with my current setup. I was just curious if i should attempt to touch it up a little by going single runner. I'm not too thrilled with the price tag that comes with the JMF manifold, but it makes sense to get one if i want to add meth....since it comes with the ports + outflows single runner stocker.

Thanks man.

I wouldn't cut out the divider unless you planned on porting the head, too. You want a smooth transition between one runner and two, so if you cut that transition out of the IM you'll need to port the head divider into a smooth transition.

I hope that makes some sense.

I do have a spare head i was planning on doing the works to...porting,+1 valves, upgraded cams and springs, etc.

Stay tuned. In the next month or so I'll be making another thread that covers our head. From what I've seen so far there really is not a lot to be gained from larger valves unless you're chasing records and have lots of money to spend. Cams and springs go hand in hand, don't do one without the other. Also, if you end up getting very aggressive cams and some stiff springs, you should definitely consider pinning the cams and keying the crank.

That is something I will be observing for part of my term project this semester. I'm very curious about this because from what I've seen so far it's not quite what I originally thought. I'll be sure to shed some more light on it when I get more conclusive results.

Very nice thread. Very informative too

I'm happy to read it because your results return the same level of imbalance i got with a leaf blower while reading a maf voltage....My flow units wasn't accurate at all but the figure returned the same conclusion...OEM manifold is a piece of crap.

I don't think we can balance it by porting like a box with 4 holes. It look more to me to be because of the flow path. That runner ask for the air to change direction when the others are facing to the natural flow direction...(not sure if my words makes sence but...)

I figured out the same imbalance with the manifold installed on the head with the valves removed. I didn't tested the head alone but i assume it is better balanced than the manifold... I will be for sure looking at your numbers and thanks you for doing it!

BTW rebuilding my engine with stock IM, the #4 piston and cylinder was like new...these tests bring me to think it may be related to the manifold...

I've been looking to get my stock mani pnp with a flow test. Didn't wanna spend the 700 bucks on a JMF if I can get some good solid, fairly equal air flow from a stocker for a fraction of the cost.

I really doubt you will get equal air flow when porting it but just a better flow with the same unbalance. I tried and didn't succeeded...the start of #4 runner is not well shaped.

A pnp machine shop with a flow tester can at least get it somewhat closer than stock? I was looking at relentless's stock pnp manifolds and I think they had said that they got the runners pretty close to equal compared to stock

If you read the post of Mazdazilla6 from the begining you will get it.
What SP3p did was balancing an aftermarket not the oem.

It is not just a matter of port size. The flow have a tendency to flow into 1-2-3 more than 4.

I wish you had did a stock manifold with VTCS delete and no porting. Just curious...

Getting rid of the VTCS and doing nothing else would have like 3-5% gains. Nothing really worth doing.

I do not doubt it would be minimal, but I have never seen any results. I was curious.

Thanks for your efforts.

I personally also wanted to see a non ported one to compare to a ported one. Lump and VTCS removed. I disagree about 3-5% gains. I think it would be closer to ported than stock but of course I am also guessing. I dont really care that much even thou that is what I have, it is more out of curiosity.

I have a stocker laying around. If I find the time I'll try to do both. No guarantees though, my schedule is pretty slammed at the moment.

Im no expert in the subject, but wont flow imbalance be insignificant when the manifold is under pressure (versus the 25inwc of the flow test)

When the manifold is pressurized (lets say with 25psi), should the manifold not be considered like a compressed air tank...if so, pressure is equally distributed everywhere and flow should be equal (or pretty damn near equal)

Just thinking :)

If that pressure remained constant perhaps it would, but we know that isn't the case.

Engines do not operate under constant pressure, this is not like at all like an air tank. The biggest difference between an engine and an air compressor is that the engine has flow. Because of that, there is never *distributed* pressure per say. Each minute area of the intake tract has its own localized pressure, general case in point, pressure is always lower after the intercooler than before it. The same is true for the intake runners as well as the plenum. Many airflow principles still apply between boosted and naturally aspirated engines.

Could the imbalance be measured with pressure transducer on each ports when doing a WOT run?

I need to rebuild my block and will go direct port injection real soon...If I could get my hand on some cheap transducers and logging hardware I could do some test by using the meth injection ports...

I don't see why it wouldn't work. It could be helpful but it doesn't paint the entire picture for us though. Flow is a function of pressure differentials and velocity, so examining pressure alone won't tell us everything about the flow.

I appreciate it. I'm curious as I am sure others are. I am getting ready to PNP and I would like to see where I stand with just a VTCS delete and how far I need to go to see significant gains, or if the gains from just a mild PNP are really worth it with the K04.

Thanks.

My vdyno is pretty spot on. I do multiple pulls both directions on same stretch of road and as close to same conditions as possible. My ported, polished, vtcs delete stocker gained about 5-10whp and wtq but it was all in midrange where I feel the k04 does not need extra power. A 3" intake and a full exhaust will max out the k04 already. The k04 is the weak point. If you are going BT do it but otherwise skip it.

I will be going BT next year or by fall. I may just go ahead and port it, but I'd like to know how much is gained just by a VTCS delete. Just do not want to kill too much bottom end either.

So i tore down my spare head and had it cleaned and ready for work (looks brand new). i'm getting overwhelmed trying to figure out exactly what parts i want to get and what needs to be done as far as porting goes. I know i want to do a gasket matched single runner down into a knife edge on the intake side since i will be getting a jmf v2 manifold. i want to gasket matched pnp exhaust side but im worried maybe that is too big for all the after market exhaust mani's available. I was wanting to go +1 intake and +2 exhaust supertech valves but others have pushed 700 awhp on stock valves and cams....so i could save the money on bigger valves and upgraded cams. but then there are the springs, dont better springs require better cams? shit just starts getting confusing. any insight or opinions you could give would be great.

Well as far as valvetrain goes, run stock springs with stock cams. The only time to consider stiffer springs with stock cams is if you plan to rev to 8k or above. IMO larger vavles are not needed at all unless you plan to squeeze everything out of the setup. Most exhaust manifolds are already gasket matched so don't worry about that. Another thing to consider is if you get stiffer springs, you're stressing the friction washers more that hold the engine in time and should consider getting the crankshaft keyed.

Ya i was already planning on having crankshaft and cams keyed as well as trying to find a way to use a heavier duty chain. As far as bigger valves and stiffer springs, i really want to do everything possible to the head and see where it gets me power wise. For PnP, i want to get rid of any sharp ledges,humps, dips, etc as well as add a mirror like finish to the exhaust side to reduce carbon buildup....not sure if doing it to the intake side would cause any harm. a local machine shop is set up to do all this as well as flow bench tests. i just need to figure out the depth of the knife edge down the runner.

There's no real reason to put a beefier chain on. SP63 made at least one engine with a sleeper chain but the amount of power it would take to actually cause the chain to fail is insane.

What are your goals for the engine? Hotter cams and stiffer springs are good and all but they also accelerate valvetrain wear so if you plan to daily the car, that might not be the greatest route. Don't bother going any smoother than a 120 grit on the intake ports.

I want to be able to DD this build. this will be a very slow build process. so if the upgraded cams and springs are not good for DD, would bigger valves be worth any significant gains staying with stock cams/springs?

In short, no. Plus you'll have less wear on the valve seats. There are definitely good gains to be had with better cams and you can run a slightly hotter cam on stock springs but there really aren't any affordable options that make it worth it.

Well there goes that dream. Guess i'll just stick with the full porting and stock valvetrain. Thanks for all your insight and help man.

Have any time to flow another intake? I can send you my new Corksport intake.