My Head Flow Numbers

Flex

Registered User
I posted this in the members only section but realize that a lot of you don't have access.

Well I finally got around to checking my head flow numbers prior to going in for my surgery. The numbers are decent for preliminary porting but I am not happy with the exhaust. Intake came in at 240 cfm and the exhaust at 166cfm. This nets an I to E ratio of 70% and is not close enough to optimal ratio that we figured was possible.

Turns out the exhaust seats were not manufactured to our request and could be hurting the head for as much as 20 cfm. My machinist and the owner of the head shop that performed the flow tests both figure that CHE sent us stuff off the shelf instead of manufacturing the seats we wanted. Sadly I had several sets of the correct seat in one of my 100 boxes of parts.

The gentleman that flowed the head figures I may be able to push the intake to 250 with some minor clean up on the short side and we are currently experimenting with a virgin head to determine if the actually seat we wanted would give us what we were trying to get for the exhaust.

He also told me that he was experimenting with a 3.8 head awhile back and thought that he may be able to put out better numbers by incorporating some of the numerous flow modifications he has uncovered over the last dozen years. His thoughts were that he could produce a better product than the heads currently offered by SSM etc. looking at the flow numbers on their sites, for less money than what they were asking and he wanted to know if there would be any interest to our members.
 
I should mention that the exhaust floors were not built up as the machinist installed the seats too quickly and we could not take a chance on the heat distorting the seat afterwards.

If the seats are coming out, I may see if it would still be possible to weld in the floors and rework the port to take advantage of the added flow that would result.
 
250cfm intake on a single port is friggin impressive. I'd like a set of those heads. hook us up!
 
Those are my own ported heads. He thinks he may be able to do even better. He has all the state of the art equipment and showed me some interesting discoveries that have been incorporated before. In discussing it with him, I suggested he under price the competition (SSM namely) in order to attract the business.
 
While this is all find and dandy, has anyone looked into how much the lower intake manifold can flow?

You may be able to get a set of heads to flow 300cfm on the intake, but if the lower intake manifold can only support 220cfm......

You have to look at the whole package, not just one little area.

Fraser
 
I posted this in the members only section but realize that a lot of you don't have access.

Well I finally got around to checking my head flow numbers prior to going in for my surgery. The numbers are decent for preliminary porting but I am not happy with the exhaust. Intake came in at 240 cfm and the exhaust at 166cfm. This nets an I to E ratio of 70% and is not close enough to optimal ratio that we figured was possible.

Turns out the exhaust seats were not manufactured to our request and could be hurting the head for as much as 20 cfm. My machinist and the owner of the head shop that performed the flow tests both figure that CHE sent us stuff off the shelf instead of manufacturing the seats we wanted. Sadly I had several sets of the correct seat in one of my 100 boxes of parts.

The gentleman that flowed the head figures I may be able to push the intake to 250 with some minor clean up on the short side and we are currently experimenting with a virgin head to determine if the actually seat we wanted would give us what we were trying to get for the exhaust.

He also told me that he was experimenting with a 3.8 head awhile back and thought that he may be able to put out better numbers by incorporating some of the numerous flow modifications he has uncovered over the last dozen years. His thoughts were that he could produce a better product than the heads currently offered by SSM etc. looking at the flow numbers on their sites, for less money than what they were asking and he wanted to know if there would be any interest to our members.


That's very impressive, considering that my new big valve CNC ported max effort heads from SCU are only flowing around 235/195.

David
 
A flow bench is not comparable to the next either. Similar to comparing dyno numbers from different cities.

Still nice that somebody local to West Coast is half decent at it.
 
That's very impressive, considering that my new big valve CNC ported max effort heads from SCU are only flowing around 235/195.

David

David,

While the Intake flow is not as high, the I to E ratio is near optimal. There is also a factor called swirl that is very important. They refer to it as "noise" and a port flowing less that is "quieter" will actually perform better.

If your heads came with a flow sheet, check to see if there are readings from a swirl meter.
 
A flow bench is not comparable to the next either. Similar to comparing dyno numbers from different cities.

Still nice that somebody local to West Coast is half decent at it.


Tom,

The tests were performed under simulated boost so the flow readings are acurate under boost conditions.

The tests were performed on a Superflow bench at 28 IN H2O which can be compared to any other Superflow measured at that level. So they are in actuality exactly comparable.

The somebody that ported these heads is me.:) The owner of the company that flowed them, John Yelich of Cylinder Head Works, has been specializing in heads for many years and we discussed the 3.8 heads for a couple of hours when I brought them in. He thinks he can outflow mine by a fair amount.
 
David,

While the Intake flow is not as high, the I to E ratio is near optimal. There is also a factor called swirl that is very important. They refer to it as "noise" and a port flowing less that is "quieter" will actually perform better.

If your heads came with a flow sheet, check to see if there are readings from a swirl meter.

What size valves are you using ?

David
 
That's very impressive, considering that my new big valve CNC ported max effort heads from SCU are only flowing around 235/195.

David

David, you can't compare the numbers due to the "simulated boost conditions" that they used. We did not simulate boost conditions due to the inherent inaccuracies of attempting to do so. Your heads can be made to generate much bigger numbers than what I presented to you.

To really compare #'s you'll have to at least perform testing in the traditional manner. Using boost simulation for development purposes is a good thing, but in the end you really need numbers that can be compared to the testing that has been done by the competition if anyone wants to draw useful comparisons.
 
David, you can't compare the numbers due to the "simulated boost conditions" that they used. We did not simulate boost conditions due to the inherent inaccuracies of attempting to do so. Your heads can be made to generate much bigger numbers than what I presented to you.

To really compare #'s you'll have to at least perform testing in the traditional manner. Using boost simulation for development purposes is a good thing, but in the end you really need numbers that can be compared to the testing that has been done by the competition if anyone wants to draw useful comparisons.

David,

Perhaps I misunderstood what John was attempting to explain to me. I will confirm it with him and get back to you. Do you check the airflow for swirl when you flow?
 
David, you can't compare the numbers due to the "simulated boost conditions" that they used. We did not simulate boost conditions due to the inherent inaccuracies of attempting to do so. Your heads can be made to generate much bigger numbers than what I presented to you.

To really compare #'s you'll have to at least perform testing in the traditional manner. Using boost simulation for development purposes is a good thing, but in the end you really need numbers that can be compared to the testing that has been done by the competition if anyone wants to draw useful comparisons.

Dave,

Bigger numbers using simulated boost method of testing, or bigger numbers from doing more work to the heads ??

I assume the test method, because I can't imagine what else could be done to improve flow except for welding on the exhaust ports to improve the short turn radius. Since that weakens the head, I don't think it's worth doing for an extra 10 or 15 CFM.

David
 
I posted this in the members only section but realize that a lot of you don't have access.

Well I finally got around to checking my head flow numbers prior to going in for my surgery. The numbers are decent for preliminary porting but I am not happy with the exhaust. Intake came in at 240 cfm and the exhaust at 166cfm. This nets an I to E ratio of 70% and is not close enough to optimal ratio that we figured was possible.

Turns out the exhaust seats were not manufactured to our request and could be hurting the head for as much as 20 cfm. My machinist and the owner of the head shop that performed the flow tests both figure that CHE sent us stuff off the shelf instead of manufacturing the seats we wanted. Sadly I had several sets of the correct seat in one of my 100 boxes of parts.

The gentleman that flowed the head figures I may be able to push the intake to 250 with some minor clean up on the short side and we are currently experimenting with a virgin head to determine if the actually seat we wanted would give us what we were trying to get for the exhaust.

He also told me that he was experimenting with a 3.8 head awhile back and thought that he may be able to put out better numbers by incorporating some of the numerous flow modifications he has uncovered over the last dozen years. His thoughts were that he could produce a better product than the heads currently offered by SSM etc. looking at the flow numbers on their sites, for less money than what they were asking and he wanted to know if there would be any interest to our members.

This sounds impressive...however have the port sizes been enlarged to the point that port velocity at part throttle will be degraded resulting in poor part throttle response?
 
This sounds impressive...however have the port sizes been enlarged to the point that port velocity at part throttle will be degraded resulting in poor part throttle response?

The exhaust ports are the same size at the exit as stock. The port itself has been ported and blended around the seat to form a smooth transition into the port.

The intakes ports at the entrance are about 1 mm smaller than the intake gaskets, but larger than stock. The walls have been ported and smoothed with concentration around the pushrod wallls.

Most of the work, again, is blending from the new seats into the walls below. A lot of the intake flow gain on the outer ports comes from flattening out the short wall under the valve.

Would this affect part throttle response, I doubt it. I have never seen any engine react adversely from head porting and I have done many over the years. My N/A 3.8 heads flowed 216 Int and 146 exhaust at .500 with stock valves and we never noticed any lack of response at any range.

I don't believe that port velocity can drop as long as the flow numbers are rising in the curve. If velocity drops, flow drops. We believe the reason that the exhaust numbers on these heads are not as high as they should be is due to the seats being too wide. This kills velocity as the "venturi" effect has been lost. The seats that we ordered and that I already had were radiused and about .200 narrower on the id.
 
Dave,

Bigger numbers using simulated boost method of testing, or bigger numbers from doing more work to the heads ??

I assume the test method, because I can't imagine what else could be done to improve flow except for welding on the exhaust ports to improve the short turn radius. Since that weakens the head, I don't think it's worth doing for an extra 10 or 15 CFM.

David


David,

Why do you think it would weaken the head? Is there any substantiation for this statement? The amount of heat that a mig or even better a tig would put into the head to build up the floor would be minimal.
 
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