Rat Bastid
Dunamis Metron
Who said make it bigger? I said IF you have to have a mismatch, make the intake bigger than the port in the head. Simple as that. Don’t make it something it’s not.
Question on port matching
- Thread starter Dan the man
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Who said make it bigger? I said IF you have to have a mismatch, make the intake bigger than the port in the head. Simple as that. Don’t make it something it’s not.
His engines are a bit powerful.
What about a basic hopped up 318’s & 360’s.
It is our opposing view point of which is better or worse, not what should be done or preferred.
Huh?
If the plan is to make as much HP as possible by port matching, which is what I thought the object of the exercise was, then what should be done is most important.
Do not know of any engine builder that recommends the intake runner should be larger where it meets the intake port at the head/manifold interface.
It is not just about airflow. It is about wet flow & velocity. It is about reversion, because a typical V8 manifold has it's runners connected to other cylinders via a plenum or plenums. A reversion pulse from a closing intake valve can affect the incoming air to another runner. A step [ smaller manifold runner opening ] at the head/manifold interface can help disrupt this damaging pulse.
Smokey Yunick says the two should be matched.
D. Vizard: 'It is a good idea to have the port in the intake a just little smaller than that in the heads.' And: 'Sometimes a precision port match actually cuts power. Why? In effect, power is dependent on how well the manifold runners manage wet flow. If there is small step at the manifold/head face junction with the intake runner being slightly smaller, the power is likely to be as good, or better than, an absolutely perfect match.',
If the plan is to make as much HP as possible by port matching, which is what I thought the object of the exercise was, then what should be done is most important.
Do not know of any engine builder that recommends the intake runner should be larger where it meets the intake port at the head/manifold interface.
It is not just about airflow. It is about wet flow & velocity. It is about reversion, because a typical V8 manifold has it's runners connected to other cylinders via a plenum or plenums. A reversion pulse from a closing intake valve can affect the incoming air to another runner. A step [ smaller manifold runner opening ] at the head/manifold interface can help disrupt this damaging pulse.
Smokey Yunick says the two should be matched.
D. Vizard: 'It is a good idea to have the port in the intake a just little smaller than that in the heads.' And: 'Sometimes a precision port match actually cuts power. Why? In effect, power is dependent on how well the manifold runners manage wet flow. If there is small step at the manifold/head face junction with the intake runner being slightly smaller, the power is likely to be as good, or better than, an absolutely perfect match.',
Thank You! This is what I was trying to say. I just could not see a big issue with an intake port that is smaller than the head port.
Of course, I was not speaking of a huge amount, which is a good point to discuss.
The question was a general one with no build level or engine stated.
Of course, I was not speaking of a huge amount, which is a good point to discuss.
The question was a general one with no build level or engine stated.
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Below is the port match on some of my stuff. This is ideal when your looking to make some really good power. The intake to head surface is smooth, level and equal all around without a surface to catch anything on. There is no argument on this from anyone I think.
What I was saying is if the intake window is smaller, this would be more desirable than having the intake window to large where the air and fuel crash into the cylinder head.
Before anyone starts saying and jumping up and down on how your going to “Kill” power, be aware that, that statement is incorrect to one degree or another. Why? Because it is a extremely broad statement to make that assumes on top of it all that the engine being discussed (no engine has been called out) is being built to make what we will call high to extreme power levels. Let’s make this level 1.4 HP per of CID to 2 HP per cube.
So that’s a 340 being built to 476 hp to 680 hp.
Port matching here is what I would call imperative for best results.
What about lower HP builds? Let’s say these are with stock heads or OOTB port sized non ported Edelbrock heads or other off shore heads on top of a stock list ones engine or one rebuilt with a compression ratio of no higher than 10- 1. We will make the power levels up to 400HP. That’s pretty easy to make. You can still use a small cam with the aluminum heads and get there.
I don’t see a “Killing” of power but won’t argue a port matching would help.
How about we take it down a notch to a cam of 224@050 with stock heads? Am I still “Killing” power!?!?!”
Best power will be made with this below.
What I was saying is if the intake window is smaller, this would be more desirable than having the intake window to large where the air and fuel crash into the cylinder head.
Before anyone starts saying and jumping up and down on how your going to “Kill” power, be aware that, that statement is incorrect to one degree or another. Why? Because it is a extremely broad statement to make that assumes on top of it all that the engine being discussed (no engine has been called out) is being built to make what we will call high to extreme power levels. Let’s make this level 1.4 HP per of CID to 2 HP per cube.
So that’s a 340 being built to 476 hp to 680 hp.
Port matching here is what I would call imperative for best results.
What about lower HP builds? Let’s say these are with stock heads or OOTB port sized non ported Edelbrock heads or other off shore heads on top of a stock list ones engine or one rebuilt with a compression ratio of no higher than 10- 1. We will make the power levels up to 400HP. That’s pretty easy to make. You can still use a small cam with the aluminum heads and get there.
I don’t see a “Killing” of power but won’t argue a port matching would help.
How about we take it down a notch to a cam of 224@050 with stock heads? Am I still “Killing” power!?!?!”
Best power will be made with this below.
Push rod pinch is a major factor in most Mopar heads!
Pushing flow towards the pinch wall is obviously bad...
Sometimes the manifold runner aims towards the pinch wall.
Making it bigger is a no no...
Imagine a water fountain from the olden days.
Very long runners getting progressively smaller, speeding up the flow.
Any areas that increase the cross section before the pinch will cause turbulence.
The only area that needs a good match is the centre runner wall.
The pinch walls are just trouble waiting to happen...
Pushing flow towards the pinch wall is obviously bad...
Sometimes the manifold runner aims towards the pinch wall.
Making it bigger is a no no...
Imagine a water fountain from the olden days.
Very long runners getting progressively smaller, speeding up the flow.
Any areas that increase the cross section before the pinch will cause turbulence.
The only area that needs a good match is the centre runner wall.
The pinch walls are just trouble waiting to happen...
Which generally works out in production assembly since the cylinder head ports to bolt and alignment stud centerlines are not that consistant.
What I’m understanding is:
Intake port window smaller than the head? No
Intake port window matched to the head? Yes. The goal.
Intake port window bigger than the head? Yes, Acceptable, Better than smaller
That’s the conclusion I come to with what RB is stating.
We all? agree Matched is the goal.
But, I always thought (from reading various articles and books over the decades) a smaller intake port window would be better than a larger port window as they meet the heads.
Has anyone tested this or know of others, have links to articles that have? (not the matching of intake/head but the larger vs smaller intake to head?)
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I posted that just as a reference of " how to" .
Rat Bastid
Dunamis Metron
This is correct. What’s your issue? I didn’t contradict myself. A smaller port in the intake is a power killer. With almost no exceptions.
Rat Bastid
Dunamis Metron
Exactly. You have serious reading comprehension issues. Do NOT make the intake smaller, and IF there is a mismatch, the port in the manifold must be bigger than the port in the head. How hard is that?
Rat Bastid
Dunamis Metron
Exactly correct. Why some are struggling with what I wrote stumps me. You never leave the intake smaller than the head. If you are going to the bother of port matching, make them the same. And if core shift or something makes it not possible to line everything up then make the manifold bigger.
All this talk of reversion, wet flow and all that is just that. The science says a step on the backside of the direction of flow will cause vortices and that is a flow killer and a power killer. If the step is in the direction of the flow, it will shear off and not develop vortices.
Think about it this way. Look at the dividers in the plenum of the manifold. The air shears off of them and finds its own way without developing vortices. And, there are times when you make the dividers sharp. As long as that edge is in the direction of flow it won’t care.
Edit: I forgot to mention how simple this is to test on a flow bench. And that is testing with relatively dry air. You need 3 different sized radius plates. Start with the correct size and make a test. Then put a radius plate on the port that is bigger than the port and see what you get. And then use a plate that is smaller than the port and see what happens.
The correct sized plate and the bigger plate will flow the same. The smaller plate will kill flow. And the port will get very noisy. Pretty simple test.
Rat Bastid
Dunamis Metron
Are you talking about Weingartner’s video where he uses dye? If so, it’s on his YouTube page.
mopowers
Well-Known Member
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.
Rat Bastid
Dunamis Metron
CNC-Dude
Well-Known Member
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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MOPAROFFICIAL
Oogliboogli
Yeah I was saying that to myself as I typed the reply . You can move it to and fro against the bias once noted which way.
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.
It depends on what the engine is built to do and how it was built.
Turbulence along the edges is not neccessarily a bad thing.
In situations where it would improve fuel distribution and make for a better combustion. Now its back to droplet size, how well it mixed in the intake and stayed in mixed. Just as important how much heat, compression, etc vaporizes and distributes the fuel once the valve is closed.
I watched so many porting videos over the last few months I couldnt remember who's it was. I looked over Erics channel but couldnt recognize which one it was.
Will you post a link ?
MOPAROFFICIAL
Oogliboogli
Tricks.
Center/common/siamese wall most critical, yes.
Opening the pincht side/dogleg window to the gasket has theoretically multiple effects. You theoretically lengthen the dogleg wall. The air speed is fixed by the cross section @ the pinch as I know it.. so length or reduction of speed 'I dont have or use a pitot' ..either way it's been useful to both ways 'port dependant' ..as has lipping I've had to learn it cave man over the years to learn what I know/think I know/and regardless of either have the ability utilize their effects.
Slightly smaller is .020
A lot is .060+
I've personally seen the anti reversion effect of a lot smaller..as in ootb intake to gasket matched head. The scenario was reminiscent of .600 lift on stock heads.
The best flowing ported iron I have is only gasket matched roof,floor,common wall and not the pinch wall at all. Bulge is paper thin however. Another crumb...assume the straight wall does not need pushed so hard. Shape.
As for the velocity drop with opening the intake up at/to the gasket...if the runner isnt as big leading up and is smaller than what you end up after gasket matching...you hurting low end power ime.
Even a magnum engine, fuel injectors just recessed inside at the windows...the stock windows have a bulge narrowing the cross section. Imo they were speeding the air to better carry/better suspend the mist.
If you gasket match that in past that...you will feel slight a lack in umph off the line. Imo you effectively moved that torque up to the 3000 rpm range.
It can all be very critical.
If driveability isn't necessary..then anyone can build a big power big rpm gas guzzling loud and stinky pos.... itll just suck everywhere out side the cam and have a mediocre average torque.
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