Can Someone Explain Head Flow Numbers Please?
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Can Someone Explain Head Flow Numbers Please? i see head flow numbers all the time, but i have no idea what any of it means? So on the Intake and Exhaust side what does the flow mean?
I have seen from .100 - .600
Thanks....
I have seen from .100 - .600
Thanks....
The .100 .600 thing would represent the lift of a cam. So if you see a head flow chart that has 300cfm at .600" that would mean if you had a cam with .600" lift you would be useing every bit of your heads (300cfm). So on down the line 275 cfm @ .550" of lift would be what your heads are flowing at the amount of lift.
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It's actually a pretty deep subject and I would like to see some of the more knowledgeable share their insight. A head's ability to make power is determined by more than just flow numbers. It's a basic measurement people use to compare heads though. The higher the numbers the better they flow, and in theory make more power. Ultimately it's all about the combo and the heads should be matched to your cam, intake, exhaust, cubic inch size, bore, and even stroke. Flow velocity is important as well, but I don't know of a measurement for this.
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The .100 .600 thing would represent the lift of a cam. So if you see a head flow chart that has 300cfm at .600" that would mean if you had a cam with .600" lift you would be useing every bit of your heads (300cfm). So on down the line 275 cfm @ .550" of lift would be what your heads are flowing at the amount of lift.
Basically i have a cam with a .588/.595 lift. I am trying to get some good heads
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It's actually a pretty deep subject and I would like to see some of the more knowledgeable share their insight. A head's ability to make power is determined by more than just flow numbers. It's a basic measurement people use to compare heads though. The higher the numbers the better they flow, and in theory make more power. Ultimately it's all about the combo and the heads should be matched to your cam, intake, exhaust, cubic inch size, bore, and even stroke. Flow velocity is important as well, but I don't know of a measurement for this.
One thing to look at is the flow #'s at .100 all the way to the .600 because the cam lobe is comming up and your valve is opening, the air/fuel is starting to enter the cylinder, so its kida like the power under the curve for cams. Also a company like afr might not have the biggest flow # on the block but they spent alot of time with the way they flow and velocity of the charge. So don't get caught up just the peak #.
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Think of it as the more the head is ported, the bigger the port becomes. Its found by filling the port with water and measuring how much water it takes to fill it.
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sorry i am jsut now starting my reserch on heads as i did when i was buying my cam
This is a combustion chamber;
This is an Intake port;
215 is the size of the intake runner.So if you have two different heads one with a 215cc runner and one with a 225cc runner and they both flow say 300 cubic feet a minuite at
.600 valve lift,the 215cc head would have better (higher) velocity because of its smaller runner size.Just talk to Chrss1313 he can help you out.
.600 valve lift,the 215cc head would have better (higher) velocity because of its smaller runner size.Just talk to Chrss1313 he can help you out.
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215 is the size of the intake runner.So if you have two different heads one with a 215cc runner and one with a 225cc runner and they both flow say 300 cubic feet a minuite at
.600 valve lift,the 215cc head would have better (higher) velocity because of its smaller runner size.Just talk to Chrss1313 he can help you out.
.600 valve lift,the 215cc head would have better (higher) velocity because of its smaller runner size.Just talk to Chrss1313 he can help you out.
What size are your 5.3 heads.. meaning what work did you do to them?
Yes, 243 casting heads would be good for you. Do whatever it takes to get the (LS6) hollow intake valves and sodium filled exhaust valves.
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Maybe the standard valves in an LS2 car would be better?
Ramp rate is your cams agresivness. Lighter valves help your cam, you can run WAY more aggressive ramps with lightweight springs, retainers, and valves.
Your ramps aren't terribly aggressive anyways if you are under .600" lift, but light weight valves are very good for valvetrain control in N/A cars.
Spring rate is the rate at which the load increases on a certain spring as you compress it. For example, lets say you have a 300 rate spring, and its installed at 2.00", and it has 100lbs of seat load at 2.00". When you squeeze that spring to 1.00" the load on the spring will now be 400lbs....... the numbers are picked for easy math, most springs will coil bind by 1.00 inch..
100lbs on the seat plus compressing the spring one inch(at 300lb/inch) equals 400lbs.
Last edited by SweetS10V8; May 13, 2009 at 11:09 PM.
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You said "spring ramp rate", which is a combo of two totally different things.
Ramp rate is your cams agresivness. Lighter valves help your cam, you can run WAY more aggressive ramps with lightweight springs, retainers, and valves.
Your ramps aren't terribly aggressive anyways if you are under .600" lift, but light weight valves are very good for valvetrain control in N/A cars.
Spring rate is the rate at which the load increases on a certain spring as you compress it. For example, lets say you have a 300 rate spring, and its installed at 2.00", and it has 100lbs of seat load at 2.00". When you squeeze that spring to 1.00" the load on the spring will now be 400lbs....... the numbers are picked for easy math, most springs will coil bind by 1.00 inch..
100lbs on the seat plus compressing the spring one inch(at 300lb/inch) equals 400lbs.
Ramp rate is your cams agresivness. Lighter valves help your cam, you can run WAY more aggressive ramps with lightweight springs, retainers, and valves.
Your ramps aren't terribly aggressive anyways if you are under .600" lift, but light weight valves are very good for valvetrain control in N/A cars.
Spring rate is the rate at which the load increases on a certain spring as you compress it. For example, lets say you have a 300 rate spring, and its installed at 2.00", and it has 100lbs of seat load at 2.00". When you squeeze that spring to 1.00" the load on the spring will now be 400lbs....... the numbers are picked for easy math, most springs will coil bind by 1.00 inch..
100lbs on the seat plus compressing the spring one inch(at 300lb/inch) equals 400lbs.
again my cam is a 28/232 .588/.595 110+4
I have to leave for work, so this will be quick. Valvetrain control is what people call valve float, and is anytime the valve isnt following the cams profile. It can be lofting over the nose (ex: you have .600" lift cam, and its throwing the valve to .620" lift). Or valve bounce, when the valve is closing it doesnt seat correctly and bounces back open.
Jonas what you want to look at for heads and flow numbers is what my dad stated...if you can find a head that has a smaller intake runner (cc size), and that flows the same during the whole lift cycle (.100-.650) as a bigger hogged out head (larger cc) then the smaller CC intake runner head will have higher velocity and create more power over the larger CC head…in a way the larger CC head has to cheat to get the flow numbers of the better designed/geometry smaller CC head…they do that by taking more material out which slows velocity down…that is why AFR’s are pretty bad ***..at only 205 CC they flow extremely well…also be careful when comparing flow numbers because some a inflated just like dyno numbers can be…
If you want the best I would say AFR 205s or trickflows…but then you are in the range of $2300-$2400
Next I would say something like TEA’s or the like LS6 price range of $1800…
Finally the 5.3s 2.5 stage PRCs for a budget head for around $1200…
now is slight added hp for the top heads worth the money over the 5.3s that is up to you but if you aren’t going max effort I would seriously consider the 5.3s…my dad has made huge power with them, maybe he will even sell you his set at the end of this summer, he has been talking about blueprinting a 347 soon…
If you want the best I would say AFR 205s or trickflows…but then you are in the range of $2300-$2400
Next I would say something like TEA’s or the like LS6 price range of $1800…
Finally the 5.3s 2.5 stage PRCs for a budget head for around $1200…
now is slight added hp for the top heads worth the money over the 5.3s that is up to you but if you aren’t going max effort I would seriously consider the 5.3s…my dad has made huge power with them, maybe he will even sell you his set at the end of this summer, he has been talking about blueprinting a 347 soon…
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