Recent Flow test with a3 heads and custom sheetmetal intake.
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Recent Flow test with a3 heads and custom sheetmetal intake.
Here is the intake sheet on a set of a3 Cleveland heads. We tested with intake the last line. Notice no drop in low flow numbers with intake on. Opinions on numbers with intake please.
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mag2555
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Re: Recent Flow test with a3 heads and custom sheetmetal intake.
At this point it can be tuff , but I would suggest this .
At the lift points where you are seing the greatest flow loss even with this canted valve head, You are still seing shrouding taking place.
And what needs to be done most times is to get the port wall over the cylinder straighter from the flange to the bowl if there is still room to rework that area, even sometimes just making it a more gentle curve can help.
Another thing to check which is very hard to discribe is this, as sometimes when a head is ported the roof gets aimed the right way during rework, but the floor does not.
If you where looking down thru the top of the head at the runner floor there is a need to have the short turn and floor angled back on the cylinder wall side , not in terms of the arc of the short turn , but the lenght of the floor from the flange to the crown of the short turn.
In other words the lenght of the floor on the cylinder wall side needs to be what it is now, but the lenght of the floor on the other side needs to be shorter.
In terms of the roof in canted valve wedge type heads you should have this shape take place as you look down the runner from the flange.
Being that the more active port wall in terms of air mass is the one over the cylinder, the short turn and the port roof need to be higher then the opposite wall, and this needs to take place gradually from the pinch point at the flange ( if there is still a pinch point) and in terms of the roof extend to each side of the short turn crown below it.
Excuse me if you know much of this already , but many others who read this may not!
At the lift points where you are seing the greatest flow loss even with this canted valve head, You are still seing shrouding taking place.
And what needs to be done most times is to get the port wall over the cylinder straighter from the flange to the bowl if there is still room to rework that area, even sometimes just making it a more gentle curve can help.
Another thing to check which is very hard to discribe is this, as sometimes when a head is ported the roof gets aimed the right way during rework, but the floor does not.
If you where looking down thru the top of the head at the runner floor there is a need to have the short turn and floor angled back on the cylinder wall side , not in terms of the arc of the short turn , but the lenght of the floor from the flange to the crown of the short turn.
In other words the lenght of the floor on the cylinder wall side needs to be what it is now, but the lenght of the floor on the other side needs to be shorter.
In terms of the roof in canted valve wedge type heads you should have this shape take place as you look down the runner from the flange.
Being that the more active port wall in terms of air mass is the one over the cylinder, the short turn and the port roof need to be higher then the opposite wall, and this needs to take place gradually from the pinch point at the flange ( if there is still a pinch point) and in terms of the roof extend to each side of the short turn crown below it.
Excuse me if you know much of this already , but many others who read this may not!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
Thanks mag. I was wondering why that dropped off there. All very interesting for sure. In a perfect world would the intake flow as good as head? Or are they most always lower.These heads had the port runners welded up to c302 size before i got them. 231cc
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mag2555
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Re: Recent Flow test with a3 heads and custom sheetmetal intake.
In a perfect world the Manifold should flow more then the head by some 3 to 5 %.
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
The intake flowed by itself should out flow the head.If not, it needs to. Attached, there is usually a restriction with any cast manifold. A well done sheetmetal intake can come in at zero restriction. I've heard of the flow boost mentioned above. I just can't make it happen.
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
What causes the restriction the angle of entry on the runners? Is this why the tunnel rams out perform a single cast 4 intake, the fuel and air is entering the port more straight and is not riding the one wall as much?
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
Lower restriction is part of gain as are SM intakes often spec'ed to the specific engine. You're right about the SM intakes usually going straight into the head for a better transition with less losses. Larger plenums help if not large enough to have recovery problems.cgarb wrote:What causes the restriction the angle of entry on the runners? Is this why the tunnel rams out perform a single cast 4 intake, the fuel and air is entering the port more straight and is not riding the one wall as much?
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mag2555
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Re: Recent Flow test with a3 heads and custom sheetmetal intake.
Many times its not what we think is restricted flow so much that knocks airflow down when even a good flowing Intake is bolted on, but the increase in port velocity made by the now longer air mass .
Many times flow testing just the Manifold itself and proving out that it is not the restriction will not make for no flow loss being seen when it's mated to the head and flow tested.
Think of this in terms of a Locomotive and a long train.
When your flowing just the head it's like just having the Loco to guide down the rails, adding the Manifold is like having a whole multi car train behind the Loco now .
Some of the curves that just the Loco could navigate on its own can not be done so by the whole train.
The whole train needs bigger radius curves in high flow areas to avoid compressing the flow which is seen as a restriction .
Many times flow testing just the Manifold itself and proving out that it is not the restriction will not make for no flow loss being seen when it's mated to the head and flow tested.
Think of this in terms of a Locomotive and a long train.
When your flowing just the head it's like just having the Loco to guide down the rails, adding the Manifold is like having a whole multi car train behind the Loco now .
Some of the curves that just the Loco could navigate on its own can not be done so by the whole train.
The whole train needs bigger radius curves in high flow areas to avoid compressing the flow which is seen as a restriction .
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
The head had been narrowed on intake like the c302 head. There was a bit of step at port entry. We filled intake with putty to see if it would change. Nothing on bench by blending entry so we decided to leave mismatch. See what it looks like on dyno.
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
So less flow equals more velocity at the same depression? Fake news?mag2555 wrote: Many times its not what we think is restricted flow so much that knocks airflow down when even a good flowing Intake is bolted on, but the increase in port velocity made by the now longer air mass .
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mag2555
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Re: Recent Flow test with a3 heads and custom sheetmetal intake.
I guess you can't grasp what I am saying?
In his situation, assuming that his Manifold was not a flow restriction ( which it seems it is not since his peak flow numbers are still near the same ) here is what might be going on.
With the Manifold bolted on his flow numbers at .500" and .600" took a hit, yet his flow at .700" was barely effected!
To me this means that at .500" to .600" lift the velocity picked up AND or the Manifolds flow pattern at those lifts shifted the flow mass to a more restricted area ( packed in ) area of the Head and in turn the flow loss was seen.
If you think this is fake news , so be it , it your disadvantage!
In his situation, assuming that his Manifold was not a flow restriction ( which it seems it is not since his peak flow numbers are still near the same ) here is what might be going on.
With the Manifold bolted on his flow numbers at .500" and .600" took a hit, yet his flow at .700" was barely effected!
To me this means that at .500" to .600" lift the velocity picked up AND or the Manifolds flow pattern at those lifts shifted the flow mass to a more restricted area ( packed in ) area of the Head and in turn the flow loss was seen.
If you think this is fake news , so be it , it your disadvantage!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
I am unclear what test is the intake test. Are the numbers in the red box W/O intake and in the blue box are WITH the intake attached? Are they both the same port even though one says cyl 1 and one says cyl 2?
Rick
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Re: Recent Flow test with a3 heads and custom sheetmetal intake.
If the manifold alignment is different to the head entry or if the manifold is curved the flow can be bias to certain parts of the port in a different manner to testing the bare head. if you take a port mold of manifold bolted to head you can see different manifold s fit well and some are terrible.
The assumption that velocity gradient at the entry of the head with a clay bellmouth will be the same velocity gradient as it would be with a intake manifold bolted is a rather large assumption. So if the flow gets more bias to the roof or floor or one side or another it will behave different. You can probably tell that the flow is being bias differently if the flow changes only at certain low and mid lifts but less at high lifts etc. i'm sure guys on here have probed the port with manifold to truly see what is going on.
Also any additional length of pipe/tube will introduce additional losses albeit potentially quite small, so you likely see small flow losses with a manifold. If it’s a short fat straight runner perfectly aligned then the losses would be lower.
I’ve always wondered if there is zero difference does it mean the manifold is too large? i mean really the manifold is an extension of the port so assuming the intake ports have the right areas then simply the additional length will knock a few CFM off at high lifts.
at the same time if the flow picks up how valid is the test and development that was done with bare head? id assume the clay bellmouth needs to be better if not replaced with a stub of some kind that provides more realistic velocity gradients. On many heads the manifold face isnt square to the port axis so the roof length and floor length are more drastically different than otherwise be the case.
The assumption that velocity gradient at the entry of the head with a clay bellmouth will be the same velocity gradient as it would be with a intake manifold bolted is a rather large assumption. So if the flow gets more bias to the roof or floor or one side or another it will behave different. You can probably tell that the flow is being bias differently if the flow changes only at certain low and mid lifts but less at high lifts etc. i'm sure guys on here have probed the port with manifold to truly see what is going on.
Also any additional length of pipe/tube will introduce additional losses albeit potentially quite small, so you likely see small flow losses with a manifold. If it’s a short fat straight runner perfectly aligned then the losses would be lower.
I’ve always wondered if there is zero difference does it mean the manifold is too large? i mean really the manifold is an extension of the port so assuming the intake ports have the right areas then simply the additional length will knock a few CFM off at high lifts.
at the same time if the flow picks up how valid is the test and development that was done with bare head? id assume the clay bellmouth needs to be better if not replaced with a stub of some kind that provides more realistic velocity gradients. On many heads the manifold face isnt square to the port axis so the roof length and floor length are more drastically different than otherwise be the case.
Re: Recent Flow test with a3 heads and custom sheetmetal intake.
The first line is avrg flow, second is without manifold and third is with. We know the head port is welded smaller to c302 size so intake runnner is the usual a3. We flowed anyway and got results above. Then we decided to putty intake as it was bigger but when we did no difference in flow once so ever. So we left as is? What we do not know is would intake on head being opened to match would gain?? A lot of guys say no. Leave it alone??