The flow numbers I have found are on quite a few different heads.
Still waiting on some more numbers, but what I have found is not very exciting.
Hughes Cams says most Mopar heads (V8) flatten out around .4 inch valve lift.
Ported heads will flow well into the .5-.6 lift range.

The trend I am seeing is around .35 for slant six heads.
There is some increase with higher lifts, but much less delta increases.
Generally speaking on the intake I see about a 25 CFM increase every .05 increase in lift.
Around .35 the increase in flow goes to lower or single digit changes in cfm.

Far from scientific collection of data, but the trend is consistent.

_________________
Hyper_pak

My junk (most of it):

Here are the goods on the head I got from Howard Davis. This is the head he was running before he made his billet head:

Valve sizes are: Exhaust - 1.45 and Intake - 1.70
Chamber volume=50cc

Lift....Intake@28"....Exhaust@28"......Ratio..E/I
200.....116.60.............95.00...............81%
300.....158.12............133.56..............84%
400.....177.00............158.12..............89%
450.....185.26............159.30..............86%
500.....188.80............159.30..............84%
550.....189.98............159.30..............84%
AVG:...169.29............144.10..............85%

Compared to the Norm Foster head flowed on the same bench:

Valve sizes are: Exhaust - 1.55 and Intake - 1.83
Chamber volume=45cc

Lift....Intake@28"....Exhaust@28"......Ratio..E/I
200.......89...................70................78.6%
300......137.................107................78.1%
400......174.................122................70.1%
450......187.................126................67.4%
500......195.................129................66.1%
530......198.................131................66.2%
550......195.................131................67.2%
600......184.................132................71.7%
AVG:...169.87.............118.50............69.7%

And the Gary Bruner head flowed on a different bench at 25"
(Seymour's Notes)

Valve sizes are: Exhaust - 1.45 and Intake - 1.78
Chamber volume=47cc

Lift....Intake@25"....Exhaust@25"......Ratio..E/I
200.....102....................93.................91%
300.....150...................141................94%
400.....183...................160................87%
500.....192...................169................88%
600.....201...................177................88%
700.....205...................181................88%
AVG:...153.50..............172.16............89%

And the milder Gerald Wright head on GodsRods Duster II (Also flowed by Gerald on the same bench as the Davis and Foster heads):

Valve sizes are: Exhaust - 1.31 and Intake - 1.61
Chamber volume=53cc(?)

Lift....Intake@28"....Exhaust@28"......Ratio..E/I
200.....103....................85.................83%
300.....143...................102................72%
400.....160...................110................69%
500.....168...................118................70%
600.....168...................118................70%
700.....168...................118................70%
AVG:...151.66..............108.50............71.5%

And last, but not least (well, actually it is the least ) is the same head as above before Gerald cleaned up the ports a little bit.

Valve sizes are: Exhaust - 1.31 and Intake - 1.61
(I think he flowed it after the valve size increase, but these numbers may be completely stock, can't remember now)

Lift....Intake@28"....Exhaust@28"......Ratio..E/I
200......90.....................87.................90%
300.....129...................104................81%
400.....141...................110................78%
500.....148...................113................77%
600.....148...................113................77%
700.....148...................113................77%
AVG:...134...................106.66...........79.6%

_________________
Rob

I’m Mater
The Kentucky Poser

Those seem like a good selection of valve size and flow #'s to have around. They should be made into a sticky because these questions about flow come up very often....

_________________
There's no such thing as too much cam....only not enough engine!

The average Intake flow on Gary's head seems to be off to me. Compared to Norm's head, it is higher at all lifts, but has a lower (153.5) average.)?? Maybe my math is off!

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Those 2 heads are different in every way from both intake and exhaust valves to the chamber size. The difference in valve sizes of course can change the average and so can chamber size. I think they each are respectable for the way they are prepped.

_________________
There's no such thing as too much cam....only not enough engine!

But Gary's head is higher in flow at every lift, but lower as an average? That makes no sense to me.

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Rob on the last 2 head numbers you list a 1.31 Exhaust Valve.
That is smaller than the stock valve.
Is that correct or a typo?
1.62 and 1.36 are stock valve sizes.

_________________
Hyper_pak

Norms head has 8 data points of reference and Gary's only has 6, that's why the average is higher....Subtract the 2 extra data points and see what you get....

_________________
There's no such thing as too much cam....only not enough engine!

Probably just a typo. My badness.

_________________
Rob

I’m Mater
The Kentucky Poser

The Intake & Exhaust avgs. are transposed...

Yes I believe you are both right.

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

When Volvo entered the British Touring Car Championship in 1994 with the 850 estate, nobody could understand how the boxy station wagon kept pulling away from the competition on long straights. The car’s secret? The inline five-cylinder engine didn’t have its head on straight—literally. Tom Walkinshaw Racing had cleverly machined a wedge out of the stock head so it sat at an angle on the block, making the inlet port steeper than stock while the exhaust port was shallower. Better breathing helped TWR “find” 65 horsepower.

_________________
Hyper_pak