Cylinder Head flow rates

[jogi730]

Does anyone have flow rate figures for a standard cylinder head - inlet and exhaust?
What increases (and figures) should you expect from a well flowed head?
And finally, what do these figures actually mean?
Are there any good links to explain the above?
Many thanks
Chris

[Bram]

From Motorgeek CFM 7A cylinderhead data:

Valve lift Intake Exhaust
.050" 40 38
.100 76 61
.150 106 92
.200 167 128
.250 186 137
.300 192 143
.350 192 149
.400 192 154

intake flow @ .500 drops

Source: http://www.motorgeek.com/phpBB2/view...=head+flow+cfm

[Bram]

10v ported cylinder head data:

"it was about 165 cfm intake, 130 exh, stock was about 130/85 or so"

Source: http://www.motorgeek.com/phpBB2/view...=109299#109299

[Bram]

stock 20v head:

"on average a stock head flows about 200cfm"

Source: http://www.motorgeek.com/phpBB2/view...=115259#115259

[Bram]

Ported 20v cylinderhead:

"Head ported and flowed, intake to 225cfm up from 190 stock "

Source: http://www.motorgeek.com/phpBB2/view...hp?p=1211#1211

So a good porting job should give approx 35 CFM increase over stock if all these numbers are correct.

[jogi730]

I do of course mean for a 20v head

[Bram]

CFM is an acronym for Cubic Feet per Minute.

Some folks measure flow from the air compressor in SCFM, but in my opinion, that’s incorrect. SCFM refers to “Standard” Cubic Feet per Minute of air, and a “Standard” Cubic Foot of air is at 68 deg. F, at sea level, with a specific humidity level, circumstances far removed from the condition of the air discharging from your compressor. For measuring the pressure coming out of the compressor, I use CFM.

You can have compressed air delivered to your application from your compressor at the correct PSI level, and the device may not work properly.

In order for blow guns, spray guns, air cylinders etc. to work satisfactorily, the compressed air has to be delivered to these devices at the correct PSI (that to generate the force required) and also at the correct flow rate ( so that your force is delivered within the acceptable time frame of the air using device).

If the air brush requires 4 PSI of air to work properly, and you supply that air through a pin hole sized tube, then the air brush is getting the correct pressure, but not enough flow to make the paint spray properly. Similarly, 30 PSI delivered to your car’s tire through that same pin hole tube will eventually fill the tire, but it will take unacceptably long time to do so.

So, when you are looking at supplying compressed air for your application remember that you have to consider the compressed air flow (CFM) and that you must have that flow at the specified pressure (PSI) to be sure to generate enough force for your device to work properly.

Source: http://wrw51.wordpress.com/2008/02/2...si-force-flow/

[Bram]

I do of course mean for a 20v head

I know, but I just make the picture complete. Might be of interest to 10V lovers as well.

[jogi730]

Ported 20v cylinderhead:

"Head ported and flowed, intake to 225cfm up from 190 stock "

Source: http://www.motorgeek.com/phpBB2/view...hp?p=1211#1211

So a good porting job should give approx 35 CFM increase over stock if all these numbers are correct.

Forgive my ignorance, but is not the exhaust side more important?

[Flat on my back]

.

As a 'wet thumb' rule an increase in flow of 20% in/out is the minimum you want to get to be able to 'feel' the difference.

Making the exhaust flow better is the most important cos of the poor design in that area in the 20v head.

[S2central.net]

I'm sort of 30% thru a DIY port job an a 7A head here - project stalled a while back thru lack of funds / space / boredom - I will eventually report back here what gains (if any) I can make. Its a spare head and I just felt the need to cut some metal on it - seemed like there is room for improvement on the factory item.

[jogi730]

From Motorgeek CFM 7A cylinderhead data:

Valve lift Intake Exhaust
.050" 40 38
.100 76 61
.150 106 92
.200 167 128
.250 186 137
.300 192 143
.350 192 149
.400 192 154

intake flow @ .500 drops

Source: http://www.motorgeek.com/phpBB2/view...=head+flow+cfm

Any info on a 3B head?

[Bram]

Should be the same as 7A I think. I thought all 20V heads were the same, flow-wise?

[stiglet]

Should be the same as 7A I think. I thought all 20V heads were the same, flow-wise?

That's what I thought

[G60Rallye]

I should have some flow figures this week for my cylinder head that has had extensive work done.