Updated Cylinder head flow numbers spreadsheet
Choosing heads based on flow numbers is like trying to determine which car is faster by looking at EPA mileage ratings.
01-17-2009, 04:16 PM
#24
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I guess I'll tell David Reher he's got it all wrong too ... rehermorrison.com - Tech Talk Article 70 - "Airflow Fallacies: Avoiding the Pitfalls of the Flow Bench".
As the saying goes..... if I had a dollar for every time I dynoed an engine with great flowing heads that didn't make any power.....well, you get the idea.
As the saying goes..... if I had a dollar for every time I dynoed an engine with great flowing heads that didn't make any power.....well, you get the idea.
01-18-2009, 09:28 PM
#25
I guess I'll tell David Reher he's got it all wrong too ... rehermorrison.com - Tech Talk Article 70 - "Airflow Fallacies: Avoiding the Pitfalls of the Flow Bench".
As the saying goes..... if I had a dollar for every time I dynoed an engine with great flowing heads that didn't make any power.....well, you get the idea.
As the saying goes..... if I had a dollar for every time I dynoed an engine with great flowing heads that didn't make any power.....well, you get the idea.
01-19-2009, 01:21 PM
#26
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That's because there are other factors at play. Which is why I said "Had you put "solely" between based and on I would agree." I find it comforting that you avoided that part of my post to justify your statement. But to bluntly say that cylinder head flow numbers are not important is foolish.
OK..... so Robin L is wrong as well?........ read...https://ls1tech.com/forums/generatio...r-heads-2.html ..... something about flow numbers being 'marketing hype'....
01-19-2009, 01:43 PM
#27
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Independant tests and taking everything in account on the end decision is the key. A good key to look for is a cylinder head that has small ports and good mid and low lift flow along with flow up top. If Im lookin at 2 sets of heads with identical flow #s through the range but one has a port 10cc smaller Im gonna go with the set that has the smaller ports. Its an indication of a better overall designed port with better velocities....in theory.
03-09-2009, 08:34 PM
#30
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exactly what bo said, a head with smaller runners that makes good flow #'s (afr..wink,wink) translate in high velocity which makes a killer street torque head. if that's what you want
03-10-2009, 12:28 PM
#31
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My webspace went away years ago, so I've removed the link and posted the spreadsheet here directly. Its a very old spreadsheet. But, it should give you some basic info...
I will say that the aftermarket heads are 1000x better than ported stock castings.
I will say that the aftermarket heads are 1000x better than ported stock castings.
03-10-2009, 12:44 PM
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OK..... so Robin L is wrong as well?........ read...https://ls1tech.com/forums/generatio...r-heads-2.html ..... something about flow numbers being 'marketing hype'....
At the bottom of the post Robin also states "Like other measuring tools it helps those of us without the knowlege of a Pro Stock team get in the ballpark".
SOOOOOO it seems like a decent TOOL to use. Obviously it isnt perfect, a dyno (or track time) is, but for those of us (all on this board most likely) that dont have the resources to hire a full time R&D department, the flow bench is pretty good.
Take flow numbers along with a builder that you trust and has proven themself knowledgable and you have a good shot at getting the right heads for your application.
03-10-2009, 01:31 PM
#34
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I'm not sure where this got off track, but I have a very long thread about flow numbers.
Lets look at a couple of facts.
Comparing flow numbers between two different benches is meaningless. There is enough fudging and variance between benches and mfgs to make that pointless.
A flow bench, like a dyno is a tool to show the delta gains. So, if your heads went from 300 to 320 cfm @ .500 lift, then you see a 20 cfm increase in flow at that lift point.
Flow numbers are one tool, just like a dyno. The other issue is that people look only at peak flow they also ignore port volume. I can make a port flow any number you want if I hog it out enough. The problem is that its hugely inefficent (or I've gone into the water jackets...
)
Tony Mamo's thread should be a place to looka t how much marketing BS and Hhype you see in flow numbers. Shops all want to compete, so they provide overly optimistic flow numbers on work. The best course of action on any head is to take it to an independant bench and check the numbers.
Lets look at a couple of facts.
Comparing flow numbers between two different benches is meaningless. There is enough fudging and variance between benches and mfgs to make that pointless.
A flow bench, like a dyno is a tool to show the delta gains. So, if your heads went from 300 to 320 cfm @ .500 lift, then you see a 20 cfm increase in flow at that lift point.
Flow numbers are one tool, just like a dyno. The other issue is that people look only at peak flow they also ignore port volume. I can make a port flow any number you want if I hog it out enough. The problem is that its hugely inefficent (or I've gone into the water jackets...
)Tony Mamo's thread should be a place to looka t how much marketing BS and Hhype you see in flow numbers. Shops all want to compete, so they provide overly optimistic flow numbers on work. The best course of action on any head is to take it to an independant bench and check the numbers.
