Cylinder Head Discussion
On The Tree
Joined: Sep 2004
Posts: 188
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From: Houston, TX
I think a good question to ask a head porter would be "How much do the heads flow over stock"? That should eliminate some of the discrepancy between the way benches read. A bench that reads high will start off with a higher than normal stock cfm number and that will be the tip-off.
Flow benches differ. Always have, always will. Some of it is the machine, some of it's the operator.
Here in Houston there are quite a few flowbenches, and a lot of us flow back and forth regularly. Oddly enough, the highest reading bench that I know of is a Superflow 1020, and the lowest reading one is a manual Superflow 600. There is 30 cfm between those two benches. My bench is right in the middle of them.
I try to keep on top of how my bench compares to others around town. I finished a set of LS6 heads a couple of weeks ago. I wanted to give the customer some independent flow numbers. I flowed one of the ports on my bench, a manual Superflow 600, then took it immediately over to SAM and troubled Casey to flow it on the schools Superflow 600 with FlowCom. That same port flowed about 5 cfm less than on my bench. That's pretty close as far as I'm concerned. My bench has always been repeateable, has never given me questionable flow numbers, and I have no intention of replacing it any time soon. I know, it's old and archaic, but a new 1020 is not going to make me a better head porter.
I think it's up to each head porter to know how his bench reads, whether it's a little higher than others, or a little low.
Flow benches differ. Always have, always will. Some of it is the machine, some of it's the operator.
Here in Houston there are quite a few flowbenches, and a lot of us flow back and forth regularly. Oddly enough, the highest reading bench that I know of is a Superflow 1020, and the lowest reading one is a manual Superflow 600. There is 30 cfm between those two benches. My bench is right in the middle of them.
I try to keep on top of how my bench compares to others around town. I finished a set of LS6 heads a couple of weeks ago. I wanted to give the customer some independent flow numbers. I flowed one of the ports on my bench, a manual Superflow 600, then took it immediately over to SAM and troubled Casey to flow it on the schools Superflow 600 with FlowCom. That same port flowed about 5 cfm less than on my bench. That's pretty close as far as I'm concerned. My bench has always been repeateable, has never given me questionable flow numbers, and I have no intention of replacing it any time soon. I know, it's old and archaic, but a new 1020 is not going to make me a better head porter.
I think it's up to each head porter to know how his bench reads, whether it's a little higher than others, or a little low.
Last edited by Greg Good; Sep 9, 2004 at 11:57 PM.
Originally Posted by FASTONE
CG99TA,whats the point of milling your heads then sinking the valves?The valve heads make up about 80% of the area in the chamber,besides sinking the valves hurts flow and changes the spring installed height.The correct solution is .030 shorter pushrods.You lose all you gain with the milling process,I mean compression if you sink the valves.
Last edited by GC99TA; Sep 10, 2004 at 04:22 AM.
Originally Posted by FASTONE
J-ROD,great post AGAIN but 276 on the intake flow??A stock 241 will flow about 250 or so at .500.All I can say is he"s not a good headporter!!Since the other guy ported his own heads and got similar results,what gives?This will be a interesting post no doubt!!
another thing to take note of is the CFM that is flown through both intakes. you'll be hard pressed to find most vendors giving you what there heads flow through any intake. besides jay and a few from brian there are none. what would you rather have, a head that flows 310 w/ a inlet plate but only 265 through an intake or one that flows 297 w/ a inlet plate but 280 through an intake.
checking and specing your **** not only allows you to see what you are actually working with but it also eliminates another avenue of potential low numbers. not implying that everyone with low numbers has bad heads but how many times have you seen posts with people upset they barely gained anything with there new cam and stg 2 heads that flow "300+" cfm.
also something to look at is the port variation. in the above example you can see its quite substantial especially with the intakes strapped on. knowing what all 4 ports flow you can get an average that will give you a better picture of the heads over a flow sheet thats just been flown on one port.
checking and specing your **** not only allows you to see what you are actually working with but it also eliminates another avenue of potential low numbers. not implying that everyone with low numbers has bad heads but how many times have you seen posts with people upset they barely gained anything with there new cam and stg 2 heads that flow "300+" cfm.
also something to look at is the port variation. in the above example you can see its quite substantial especially with the intakes strapped on. knowing what all 4 ports flow you can get an average that will give you a better picture of the heads over a flow sheet thats just been flown on one port.
Last edited by jrp; Sep 10, 2004 at 06:25 AM.
On The Tree
Joined: Sep 2004
Posts: 188
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From: Houston, TX
The intake port needs to flow as much as possible with a radiused orifice.
How much an intake manifold drops a head is an indication of how good or bad the manifold is, not the head.
If you have a really good flowing head and the intake drops it a bunch, you need a new intake.
How much an intake manifold drops a head is an indication of how good or bad the manifold is, not the head.
If you have a really good flowing head and the intake drops it a bunch, you need a new intake.
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TECH Senior Member
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One thing though I wouldnt label the advent of CNC machining as a "Problem" as you have stated:
Problem two: The proliferation of low cost CNC heads makes it economically difficult for the shops doing hand porting to be able to devote the man hours necessary to a set of heads that they may need while still remaining profitable.
If they (hand porters) dont adapt and buy a CNC machine it is THEIR problem NOT the consumer.
The hand porter should design the port and then have it digitized for CNC. They can then hand finish or do whatever they want to it afterwards.
The introduction of CNC ported heads is a WONDERFUL thing for us as consumers. Precision, repeatability and mass production.
Problem two: The proliferation of low cost CNC heads makes it economically difficult for the shops doing hand porting to be able to devote the man hours necessary to a set of heads that they may need while still remaining profitable.
If they (hand porters) dont adapt and buy a CNC machine it is THEIR problem NOT the consumer.
The hand porter should design the port and then have it digitized for CNC. They can then hand finish or do whatever they want to it afterwards.
The introduction of CNC ported heads is a WONDERFUL thing for us as consumers. Precision, repeatability and mass production.
TECH Fanatic
Joined: May 2003
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From: RainbowCity,Alabama
Originally Posted by SStrokerAce
When you get into economical head wars then you start seeing lower quality parts installed on the heads to keep the prices down. It's a fact of life. If we had higher quality valves, retainers, springs etc.... on the heads you could easily see a huge price jump if they had those types of parts in them.
Thread Starter
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
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From: Texas
Originally Posted by Chris ARE 385
One thing though I wouldnt label the advent of CNC machining as a "Problem" as you have stated:
Problem two: The proliferation of low cost CNC heads makes it economically difficult for the shops doing hand porting to be able to devote the man hours necessary to a set of heads that they may need while still remaining profitable.
If they (hand porters) dont adapt and buy a CNC machine it is THEIR problem NOT the consumer.
The hand porter should design the port and then have it digitized for CNC. They can then hand finish or do whatever they want to it afterwards.
The introduction of CNC ported heads is a WONDERFUL thing for us as consumers. Precision, repeatability and mass production.
Problem two: The proliferation of low cost CNC heads makes it economically difficult for the shops doing hand porting to be able to devote the man hours necessary to a set of heads that they may need while still remaining profitable.
If they (hand porters) dont adapt and buy a CNC machine it is THEIR problem NOT the consumer.
The hand porter should design the port and then have it digitized for CNC. They can then hand finish or do whatever they want to it afterwards.
The introduction of CNC ported heads is a WONDERFUL thing for us as consumers. Precision, repeatability and mass production.
When you do them by hand, you can control where you hit the port.
Another important part of CNC work that often gets overlooked is tool path. You can take the same port and digitize it, and adjust the tool path and totally ruin the way the port works.
I agree that CNC is a way to obtain repeatability. I like CNC, don't get me wrong. My point about CNC is that when you have a CNC head that flows about 95% of what a good hand ported head flows at half the price, its sometimes hard to justify that extra expense. Hence for the hand porter they must either loose customer base, or cut cost. To cut cost you have to do less work on the head or drop your per/hr rate. In most cases you end up doing both. When you cut corners, quality can suffer, its just a fact.
So, you are right back to what I was talking about. If they spent more time, then you get the number, if they have to shave a bit of time off, well, the heads are good, but maybe they are down 10 or 15CFM over what you'd expect.
On The Tree
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From: TEA
Originally Posted by GC99TA
But if your little 
thing was an attempt to make me look stupid, I can do with out it. No hard feelings though, I've got thick skin and this is a tech thread, not preschool.
sorry didn't mean to get you all excited
So it sounds like you have some expierience with sinking the valves to regain piston to valve clearance. What is the typical loss in flow that you have seen with this method?
thing was an attempt to make me look stupid, I can do with out it. No hard feelings though, I've got thick skin and this is a tech thread, not preschool. sorry didn't mean to get you all excited
So it sounds like you have some expierience with sinking the valves to regain piston to valve clearance. What is the typical loss in flow that you have seen with this method?
mostly low to mid lift loss but i have seen that to cause a port to stall
that may be atributed to buy it having less of a short turn after the sinking
TECH Enthusiast
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From: Foley, Alabama-southern Alabama
A local porter that ports all kinds of heads said its no problem to get 300 cfm with the stock 2.0 valve on a superflo 600 flowbench,as he's done it before !!!As mentioned flowbenches can vary a lot!! 
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From: Foley, Alabama-southern Alabama
GC99TA,when you cc a head the fluid goes in the chamber itself not on the flat part or deck of the head,so this area has nothing to do with chamber volume.I f you mill a head this flat stays in the same place on top of the head gasket,you gain no compression.Only volume in the chamber will change the cr. on the head itself!!
TECH Senior Member
Joined: Nov 2001
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Originally Posted by J-Rod
True to some extent, but you have core shift on stock heads. In many cases you can have a CNC program, and once you have your port dialed in, if the port has moved around, you may not end up touching the port in certain places. Once you open up the program to take into account core shift you may pick up 10-15CC in the runner size to ensure you hit it thoroughly.
When you do them by hand, you can control where you hit the port.
Another important part of CNC work that often gets overlooked is tool path. You can take the same port and digitize it, and adjust the tool path and totally ruin the way the port works.
I agree that CNC is a way to obtain repeatability. I like CNC, don't get me wrong. My point about CNC is that when you have a CNC head that flows about 95% of what a good hand ported head flows at half the price, its sometimes hard to justify that extra expense. Hence for the hand porter they must either loose customer base, or cut cost. To cut cost you have to do less work on the head or drop your per/hr rate. In most cases you end up doing both. When you cut corners, quality can suffer, its just a fact.
So, you are right back to what I was talking about. If they spent more time, then you get the number, if they have to shave a bit of time off, well, the heads are good, but maybe they are down 10 or 15CFM over what you'd expect.
When you do them by hand, you can control where you hit the port.
Another important part of CNC work that often gets overlooked is tool path. You can take the same port and digitize it, and adjust the tool path and totally ruin the way the port works.
I agree that CNC is a way to obtain repeatability. I like CNC, don't get me wrong. My point about CNC is that when you have a CNC head that flows about 95% of what a good hand ported head flows at half the price, its sometimes hard to justify that extra expense. Hence for the hand porter they must either loose customer base, or cut cost. To cut cost you have to do less work on the head or drop your per/hr rate. In most cases you end up doing both. When you cut corners, quality can suffer, its just a fact.
So, you are right back to what I was talking about. If they spent more time, then you get the number, if they have to shave a bit of time off, well, the heads are good, but maybe they are down 10 or 15CFM over what you'd expect.
Also a CNC is FAR more precise than a hand port period. There is no comparision really.
Especially within different ports/chambers within the same head. I have seen top hand ported heads with quite a bit of variance between ports on the same head.
If the port is designed properly and digitized properly it'll be Ultra accurate. The amount of work need to be done by hand GREATLY reduced and with a good hand finish it'll be super repeatable and consistent flow wise.
On The Tree
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Originally Posted by FASTONE
A stock vortec sb head will flow 225 cfm so a ls1 is only 5 better?A stock ls1 flows about 250!!At .500 at .550 and.600!! 
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From: Working in the shop 24/7
The old flow numbers game huh...
Well...
People who buy cylinder heads based solely on advertised flow figures are like some people on a diet...
Instead of using the same scale to see what the results of the diet really are, they search high and low for a scale that reads the number that they want to weigh. Then "that's" the real figure...
Flow benches are TOOLS to be used to make something better...
Forget all the "advertised" numbers. Ask for the DELTA between the starting point and the finish point. There's the real key to how good the port work is...
What if someone shows up with a 310 cfm @ .600" head on XYZ's bench... Nice number... But what was the "base" number on XYZ's bench before the porting? There inlies the head's true potential over it's stock configuration...
Enough... this thread should get good so I'm making some popcorn and standing by..
Ed
Well...
People who buy cylinder heads based solely on advertised flow figures are like some people on a diet...
Instead of using the same scale to see what the results of the diet really are, they search high and low for a scale that reads the number that they want to weigh. Then "that's" the real figure...
Flow benches are TOOLS to be used to make something better...
Forget all the "advertised" numbers. Ask for the DELTA between the starting point and the finish point. There's the real key to how good the port work is...
What if someone shows up with a 310 cfm @ .600" head on XYZ's bench... Nice number... But what was the "base" number on XYZ's bench before the porting? There inlies the head's true potential over it's stock configuration...
Enough... this thread should get good so I'm making some popcorn and standing by..
Ed
Originally Posted by FASTONE
GC99TA,when you cc a head the fluid goes in the chamber itself not on the flat part or deck of the head,so this area has nothing to do with chamber volume.I f you mill a head this flat stays in the same place on top of the head gasket,you gain no compression.Only volume in the chamber will change the cr. on the head itself!!
J-rod,
Where should we be at now in terms of the discussion process? Still focussing in on flow numbers?
Its plain and simple to see that alot of the flow number wars are unrealistic. I think Ed's post is good. A way we can detect flow number BS.
good thread
Where should we be at now in terms of the discussion process? Still focussing in on flow numbers?
Its plain and simple to see that alot of the flow number wars are unrealistic. I think Ed's post is good. A way we can detect flow number BS.
good thread