Question on port matching

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mopowers said:
In the latest Engine Masters episode, Freiburger mentioned at the beginning that the worst case scenario is having the intake port larger that the port in the head. Lots of differing opinions on this. What it tells me is that having the ports matched is the best scenario. In the majority of cars on this forum though, I'd doubt anyone would ever notice the difference either way.
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I believe the part in bold very much.
I also think the same on no one will ever now or notice but only on low power builds.

Rat Bastid said:
Yeah, I have to go find that episode because if that’s what he said he is wrong.
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I think the video you showed has a flaw in its science when comparing it to the intake/cylinder head. The fluid dynamics seen are moving slow. Even if the fluid in the video is moving at 100 mph. It’s slow compared to the intake charge. While I could easily see something of the sort developing at the off set mating surfaces, I am hard pressed to believe a small off set would cause this.
Speaking of which, what kind of offset are we speaking about. You haven’t answered that one yet. I find it critical to define this and a exact measurement or percentage of a port size would be acceptable. This should also be weighed against an known CID of an engine.

It was mentioned that David Vizard said the tow should be matched but also in some cases the smaller intake port window made more power. It must be a case of slightly better velocity.

The old MP books state the same as I was saying. If the ports are not matched, the intake should be smaller. A larger intake port than head port has the air and fuel crashing into the cylinder head causing issues and power losses.

Disclaimer, I ain’t that smart. But I’m smart enough to follow the smart guys. It’s even better when they have been there and done that.

Let’s see, MP engineers agree with me…
David Vizard also thinks this way….
Rat Bastard doesn’t….
Without trying to be a mean dickhead or belittling, I’ll follow the DC books and Mr. Vizard before an unknown fella from the internet. Claiming the exact opposite with (IMO) flawed fluid dynamic videos.

I am open to the idea I’m wrong. But I don’t think so. I’ll need some hard proof and not someone saying it’s so.

As a side note, IDGAF what the Chevy guys did and how well it worked. Just sayin….

@pittsburghracer I have two things for you, so, first up is, I hope you know this, where can one get a smoke machine to show the air flow down a intake and cylinder head. I’ve seen these on YouTube before. Any ideas?
:thankyou:

Secondly! Ceral first, milk second.
:thumbsup:
 
pittsburghracer said:
You guys are scaring the hell out of me. I may never port an intake manifold again in my life. Now you have me thinking about everything I do. When making cereal should I put the cereal in the bowl first or the milk. I’m confused.
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It depends.
Like Basic 4, probably milk 1st.
The flakes are honey coated little bowls that deflect the milk all over the counter.:D
 
Fluid doesnt move just like air, it's a cousin sisters brother... 'close relative' but the fluid/liquid will continue on mostly while the air hangs a left turn..
 
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Exactly!!! Hence why I think the idea path is on the right track but flawed in practice.
 
Say the port has some turbulence..open the clay radius a hair bigger at the floor...and slow/tumble it to 'seemingly' stability lol
 
rumblefish360 said:
I believe the part in bold very much.
I also think the same on no one will ever now or notice but only on low power builds.


I think the video you showed has a flaw in its science when comparing it to the intake/cylinder head. The fluid dynamics seen are moving slow. Even if the fluid in the video is moving at 100 mph. It’s slow compared to the intake charge. While I could easily see something of the sort developing at the off set mating surfaces, I am hard pressed to believe a small off set would cause this.
Speaking of which, what kind of offset are we speaking about. You haven’t answered that one yet. I find it critical to define this and a exact measurement or percentage of a port size would be acceptable. This should also be weighed against an known CID of an engine.

It was mentioned that David Vizard said the tow should be matched but also in some cases the smaller intake port window made more power. It must be a case of slightly better velocity.

The old MP books state the same as I was saying. If the ports are not matched, the intake should be smaller. A larger intake port than head port has the air and fuel crashing into the cylinder head causing issues and power losses.

Disclaimer, I ain’t that smart. But I’m smart enough to follow the smart guys. It’s even better when they have been there and done that.

Let’s see, MP engineers agree with me…
David Vizard also thinks this way….
Rat Bastard doesn’t….
Without trying to be a mean dickhead or belittling, I’ll follow the DC books and Mr. Vizard before an unknown fella from the internet. Claiming the exact opposite with (IMO) flawed fluid dynamic videos.

I am open to the idea I’m wrong. But I don’t think so. I’ll need some hard proof and not someone saying it’s so.

As a side note, IDGAF what the Chevy guys did and how well it worked. Just sayin….

@pittsburghracer I have two things for you, so, first up is, I hope you know this, where can one get a smoke machine to show the air flow down a intake and cylinder head. I’ve seen these on YouTube before. Any ideas?
:thankyou:

Secondly! Ceral first, milk second.
:thumbsup:
Click to expand...


It’s not a flaw in the science. The speed of the fluid will only make the vortices worse. So what speed they used in the video really doesn’t matter. You get the idea of what’s happening.

David Vizard has never been wrong.
MP has never been wrong.

Surely I jest. You can believe what you want, but that won’t change the science of it. I suspect you’ve never had any time on a flow bench, and that your porting experience is limited. Otherwise you would be able to grasp this very easily.

Turbulence isn’t always bad, but vortices are always bad. In fact, I could post some Darin Morgan videos that show exactly what I’m talking about but I won’t bother. It shows the opposite of Vizard and the MP stuff so he must be wrong too.
 
MOPAROFFICIAL said:
Fluid doesnt move just like water, it's a cousin sisters brother... 'close relative' but the fluid/liquid will continue on mostly while the air hangs a left turn..
Click to expand...


Exactly. And that’s exactly what the videos I posted show. Those vortices cause fuel separation and that’s bad. And the change in section changes the pressure in the port which does the exact same thing. So doing a gasket match and making a big expansion at the manifold/head will kill power.
 
CNC-Dude said:
Just to throw this curve out here, but first I am an avid pro port match advocate. I raced Big Block Chevy's for over 20 years. Many racers had a common practice of putting a square port intake on an engine that had round port heads. I did it many times myself and it made more HP than with the same intakes made for round port heads. With a round port intake on round port heads, it would stumble and buck and jump at lower rpm's on the street(engine made 600 HP in a street car) and not really good street manners. Put a square port intake on it and you could lug the engine down to 1000 rpm without down shifting(straight shift car) and accelerate moderately at it would take off smooth as glass. Car ran 7.00's in the 1/8 with the round port intake and jumped to 6.80's same day, same carb and weather condtions with the square port intake. To put this into Mopar speak, that's like putting a Max Wedge intake on 906 or 452 heads. That's how big the mismatch was. I know several Big Block Mopar racers that have done the Max Wedge intake on 906 heads also and ran great. It totally contradicts what Frieburger is said to have said, but this has been done over 30 years by many, many Chevy guys and can be validated.
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A pic of the 2 laid over eachother would explain it. Fuel ..if I'm imagining this right.. is being picked up by the lip/speed bumps...its tumbling the air. Like the clay radius example..except its fuel now being kicked back up into suspension at low rpm/velocity operation
 
As I understood it the a/f crashing into the ledge of the smaller head ports helps mix the A/F .
It was interesting to see how the a/f seperate in certain situations.
 
Rat Bastid said:
It’s not a flaw in the science. The speed of the fluid will only make the vortices worse. So what speed they used in the video really doesn’t matter. You get the idea of what’s happening.

David Vizard has never been wrong.
MP has never been wrong.

Surely I jest. You can believe what you want, but that won’t change the science of it. I suspect you’ve never had any time on a flow bench, and that your porting experience is limited. Otherwise you would be able to grasp this very easily.

Turbulence isn’t always bad, but vortices are always bad. In fact, I could post some Darin Morgan videos that show exactly what I’m talking about but I won’t bother. It shows the opposite of Vizard and the MP stuff so he must be wrong too.
Click to expand...

True true true all around. Zero bench and minor porting experience.

So doing a gasket match and making a big expansion at the manifold/head will kill power.
Click to expand...
A Big expansion at the manifold to the head?

A Darin Morgan video? SURE! Serve it up! Absolutely!
 
rumblefish360 said:
True true true all around. Zero bench and minor porting experience.

A Big expansion at the manifold to the head?

A Darin Morgan video? SURE! Serve it up! Absolutely!
Click to expand...
This topic got over my head rather quick. I don't have a flow bench or the means to be able to have a intake manifold or cylinder heads on a flow bench. I don't think that it would affect what I'm going to be doing anyway, was just wondering the best method for port matching and if it would be worth me having done since a friend of mine will do it for cheap.
 
Dan the man said:
This topic got over my head rather quick. I don't have a flow bench or the means to be able to have a intake manifold or cylinder heads on a flow bench. I don't think that it would affect what I'm going to be doing anyway, was just wondering the best method for port matching and if it would be worth me having done since a friend of mine will do it for cheap.
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I try to keep things simple because of this. It’s not anywhere near as difficult as this post makes it appear. Carry on guys.
 
pittsburghracer said:
I try to keep things simple because of this. It’s not anywhere near as difficult as this post makes it appear. Carry on guys.
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It’s not difficult to do, but it’s easy to screw it up. Changes in cross section affect way too much to not understand what happens when you do it. You do a lot of work with your pitot tube so you know exactly what I’m saying.

Going in and opening up the port window in the head and intake without addressing the rest of the port and manifold will surely show a power loss.
 
rumblefish360 said:
True true true all around. Zero bench and minor porting experience.

A Big expansion at the manifold to the head?

A Darin Morgan video? SURE! Serve it up! Absolutely!
Click to expand...


Give me a bit and I’ll see if I can find exactly which video he has that covers the vortices and such.
 
Rat Bastid said:
Give me a bit and I’ll see if I can find exactly which video he has that covers the vortices and such.
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Why don't you just make your own video ?
you are a 100% correct on your intake manifold theory.
 
Ok, this is part 1 of 3. You need to watch all 3 of them. You do that and you’ll understand what I’m saying.



You should be able to find parts 2 and 3 when you get to this one.
 
Rat Bastid said:
I find it almost comical that people think a smaller port dumping into a larger port is a good thing.
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By how much? You still haven’t answered that question.
Glad you find other peoples lack of knowledge comical.
Your starting to remind me of a certain 302 head lover

Rat Bastid said:
Ok, this is part 1 of 3. You need to watch all 3 of them. You do that and you’ll understand what I’m saying.



You should be able to find parts 2 and 3 when you get to this one.
Click to expand...

Thank you
 
rumblefish360 said:
By how much? You still haven’t answered that question.
Glad you find other peoples lack of knowledge comical.
Your starting to remind me of a certain 302 head lover


Thank you
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Ive already said it. NONE. Never make the port in the manifold smaller than the head. Ever. I realize you have to change your thinking to get it, but it’s still the fact. Watch the Morgan videos. The last thing you want in any system is corners. The next worse thing is changes in section. And then a mismatch going with the flow.
 
Something to think about from a very sharp engine builder I wont name.

"I ported some heads for a 400" late model last year, the guy couldn't afford a new intake at the time & the intake he had was a shitty old holley strip dominator - not a great intake at the best of times & completely unsuited to the engine, so not worth spending any $$ to port it.
It was left alone with the intention of replacing it with a ported super victor when the coin was available.
I picked up something like 40cfm from those heads - & guess what, the motor picked up 60hp at the wheels without touching the intake.
The intake runners at the head face are a LOT smaller than the ports in the head, yet it still made considerably more power with the port work to the heads - much more power than a constant flow flow test to the intake would say was possible."

Maybe just maybe it gives the fuel that's on the walls and floor a chance to get re-entrained in the air column. He also mentioned a manifold murdering the intake flow on a head on the flow bench but not seeing a corresponding drop in power with the loss of airflow to what the engine actually made. In other words the murder in airflow didn't translate into a murder of the power the engine ultimately made.

Maybe go look at what Ethyl Corp found when they isolated the fuel that ended up on the intake runner walls and how that affected afr distribution. Considering pump gas uses a lot heavy end distillates that require a lot of heat to vaporize and they most likely will end up on the walls and floor.......
 
Rat Bastid.
None of the you tube videos in this thread support your contention that the opening in the intake man where it meets the head should be bigger & that it helps power because a smaller opening kills power, posts 28,40, 89. You mention fluid dynamics.
Water is a fluid. To duplicate the above scenario, where the port in the head is smaller & overhangs, get a garden hose & aim it at the corner of your house. See if you get smooth flow...
 
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