Originally Posted by Stang's Bane

I can understand that, however this thread is about a no holds barred n/a motor.

Originally Posted by Patrick G

My reference to Brian Tooley's quote was in regards to the TFS headed car running a plastic intake spanking an ETP headed motor with a sheet metal intake. When running a plastic intake, you can expect diminishing returns once you exceed a certain flow number, even with an LS7 intake, hence the dependance on strong mid-lift flow numbers.


Also, you can't make a blanket statement that a larger 2.20" intake valve should flow more air than a 2.08" valve because you also have to consider chamber and bore shrouding. The larger the intake valve, typically the more the valve will encounter shrouding from the chamber wall and cylinder bore. In the case of the TFS head, they get superior mid-lift flow by running a smaller valve and positioning it further away from the chamber wall and bore.

In a nutshell, this illustrates that it does not take a no-holds-barred approach to make 600 rwhp. Making 700 rwhp probably would. In that case, much higher compression, solid roller cam, and a head/intake combo that is geared to ingest more air than one running a plastic intake.

Originally Posted by Patrick G

My reference to Brian Tooley's quote was in regards to the TFS headed car running a plastic intake spanking an ETP headed motor with a sheet metal intake. When running a plastic intake, you can expect diminishing returns once you exceed a certain flow number, even with an LS7 intake, hence the dependance on strong mid-lift flow numbers.


Also, you can't make a blanket statement that a larger 2.20" intake valve should flow more air than a 2.08" valve because you also have to consider chamber and bore shrouding. The larger the intake valve, typically the more the valve will encounter shrouding from the chamber wall and cylinder bore. In the case of the TFS head, they get superior mid-lift flow by running a smaller valve and positioning it further away from the chamber wall and bore.

In a nutshell, this illustrates that it does not take a no-holds-barred approach to make 600 rwhp. Making 700 rwhp probably would. In that case, much higher compression, solid roller cam, and a head/intake combo that is geared to ingest more air than one running a plastic intake.

Originally Posted by Forteen3GT

Tooley again........

I am willing to put a bet that a 454 with a 2.20 intake valve has better flowing heads then a 408 with a 2.08 valve.... shrouding is not an issue with a smaller bore. If both intakes have the same cross sectional area and equal FPM..... it is mute to argue that the smaller valve heads will flow more.

Cant wait to see what a real L92 head flows! 2.125 intake and 1.60 exhaust for the win..... on a 408 btw. I am looking for 510-520 thru the TH400, big stall, heavy wheels.

btw; logic does tend to agree with him about over valving a head/bore. Too much is a bad thing....

IMO, LSX block, 4.1 crank, EWP, Pulley, ET LS7 heads, Sheetmetal intake, T-56, and 17 inch stock wheels....... = 600 N/A RWHP all day long!

Wonder if it is do-able with a set of small valve L92 heads and a L92 block??

Originally Posted by Stang's Bane

I can understand that, however this thread is about a no holds barred n/a motor.

Originally Posted by Stang's Bane

I can understand that a bigger valve is different to cam, maybe even harder for some, but to say there are no benefits to one is ridiculous. It is much easier to get flow out of a larger valve. That is the reason iit is done, period. It makes good sense (to me!!)that a larger valve will like more lift to hit the peak flow on it than a smaller valve.

Originally Posted by Stang's Bane

For Brian to make a blanket statement that .400 lift is the most important number is hard for me to digest. To me and my simple little mind, it seems like each lift point that a valve passes on the way to peak lift would be equally important. Doesn't it pass all of these points twice? Won't the lift point at which peak intake flow occurs help decide what lift point is the most important? I can theoretically understand how one point will be most influential in the range of lift, but like anything else, other factors will determine what that point is.

Originally Posted by Brian Tooley

He was looking for 600 RWHP combo's so I gave him one, with pump gas and a hyd roller cam no less.



Your right, it is easier to get flow out of a larger valve, now how much easier does the larger intake valve flow BACKWARDS? This is not some theory I came up with, this is what we have found in testing. You have to look at when the intake valve closes during the compression stroke, the piston is a full 1/3 the way up the bore during the compression stroke BEFORE the intake valve closes, it is during this time that a bigger intake valve is much more likely to suffer from intake port reversion, or the charge going back INTO the intake port. This is not the best way to build HP on a street/strip car. GM used that size valve because they were using VERY short intake cam durations, and that combination works well together.



I tend to say mid lift flow is most important on a street/strip car (.300"-.500"), but with the .400" flow number being in the middle, it is easy to say it is the most important, because if you have a killer .400" flow number, the chances are very good that the .300" and .500" are also going to be very good, and that is what makes power. For a race engine you can move that up .100", so the .400"-.600" flow numbers become the most important, and I don't care if you are using 1.000" of cam lift, the mid lift flow is what makes the power.

You have to bear in mind that we have shipped thousands of heads over the years, have been involved in numerous heads up racing organizations, have set probably close to a hundred records and have had dozens of class champions. You can take my cousin Sam Vincent for example, he has been running the same set of Brodix Neal 318 heads from us for 4 years. He just won the Outlaw World Ford Challenge as well as the last NMRA Outlaw race and holds the record. He has a 440 cu in Small block Ford with nitrous on a tiny 28"x10.5" tire, the engine makes over 900 HP on motor with a cast intake and has run 7.40's @ 187 mph on the spray. His heads flow 360 cfm at .500" lift, once again, what I would consider to be the most important flow number for a race engine and right in the middle of his mid lift of .400"-.600" and he does run over 1.000" of intake lift.

The mid lift flow is so much more important than peak flow due to the fact that the cylinder isn't packed with air at the point of peak lift, it is packed with air when the piston is at the bottom of the intake stroke and is coming back up the bore during the compression stroke. This is called volumetric efficiency, ever think about how you can put 110%-120% of atmospheric pressure in a cylinder? Atmospheric pressure is around 14.7 psi, so you would be putting 16-17 psi of pressure into the cylinder! The valve is closing as the piston approaches bottom dead center and the air is still moving forward, then the piston reaches bottom dead center and starts moving up the bore, and the air is still flowing, if you have enough velocity. The SAME amount of airflow around a smaller valve yields MORE velocity. The more airflow that is available at these mid lift points (.300"-.500") the more air is going to continue to pack the cylinder, at some point the pressure in the cylinder overcomes the pressure of the forward moving mass of air, at that point you have intake port reversion. It is at this exact point that you would want to close the intake valve. Smaller intake valves make your low lift flow lower, the lower your low lift flow is (.100"-.200") the lesser your chance of intake reversion. So the smaller intake valves act more like a "check valve" (if you know what that is) to intake port reversion. The lesser your chance of intake reversion, the easier the engine is to cam and is then easier to make power.

So the bottom line is the intake mid lift is MOST IMPORTANT for making power, regardless of intake used or ANY other factor.

If you can get the same amount of airflow out of a smaller valve it will tend to make more power easier. So you can see why we feel that the TFS heads flowing about what a very well ported L92 or a factory LS7 with a MUCH smaller valve is easier to make power with, it is less sensitive to cam timing. Basically, as you shove more duration at the TFS heads they tend to make more power, you cannot say that about the big valve heads.

Originally Posted by Brian Tooley

He was looking for 600 RWHP combo's so I gave him one, with pump gas and a hyd roller cam no less.



Your right, it is easier to get flow out of a larger valve, now how much easier does the larger intake valve flow BACKWARDS? This is not some theory I came up with, this is what we have found in testing. You have to look at when the intake valve closes during the compression stroke, the piston is a full 1/3 the way up the bore during the compression stroke BEFORE the intake valve closes, it is during this time that a bigger intake valve is much more likely to suffer from intake port reversion, or the charge going back INTO the intake port. This is not the best way to build HP on a street/strip car. GM used that size valve because they were using VERY short intake cam durations, and that combination works well together.



I tend to say mid lift flow is most important on a street/strip car (.300"-.500"), but with the .400" flow number being in the middle, it is easy to say it is the most important, because if you have a killer .400" flow number, the chances are very good that the .300" and .500" are also going to be very good, and that is what makes power. For a race engine you can move that up .100", so the .400"-.600" flow numbers become the most important, and I don't care if you are using 1.000" of cam lift, the mid lift flow is what makes the power.

You have to bear in mind that we have shipped thousands of heads over the years, have been involved in numerous heads up racing organizations, have set probably close to a hundred records and have had dozens of class champions. You can take my cousin Sam Vincent for example, he has been running the same set of Brodix Neal 318 heads from us for 4 years. He just won the Outlaw World Ford Challenge as well as the last NMRA Outlaw race and holds the record. He has a 440 cu in Small block Ford with nitrous on a tiny 28"x10.5" tire, the engine makes over 900 HP on motor with a cast intake and has run 7.40's @ 187 mph on the spray. His heads flow 360 cfm at .500" lift, once again, what I would consider to be the most important flow number for a race engine and right in the middle of his mid lift of .400"-.600" and he does run over 1.000" of intake lift.

The mid lift flow is so much more important than peak flow due to the fact that the cylinder isn't packed with air at the point of peak lift, it is packed with air when the piston is at the bottom of the intake stroke and is coming back up the bore during the compression stroke. This is called volumetric efficiency, ever think about how you can put 110%-120% of atmospheric pressure in a cylinder? Atmospheric pressure is around 14.7 psi, so you would be putting 16-17 psi of pressure into the cylinder! The valve is closing as the piston approaches bottom dead center and the air is still moving forward, then the piston reaches bottom dead center and starts moving up the bore, and the air is still flowing, if you have enough velocity. The SAME amount of airflow around a smaller valve yields MORE velocity. The more airflow that is available at these mid lift points (.300"-.500") the more air is going to continue to pack the cylinder, at some point the pressure in the cylinder overcomes the pressure of the forward moving mass of air, at that point you have intake port reversion. It is at this exact point that you would want to close the intake valve. Smaller intake valves make your low lift flow lower, the lower your low lift flow is (.100"-.200") the lesser your chance of intake reversion. So the smaller intake valves act more like a "check valve" (if you know what that is) to intake port reversion. The lesser your chance of intake reversion, the easier the engine is to cam and is then easier to make power.

So the bottom line is the intake mid lift is MOST IMPORTANT for making power, regardless of intake used or ANY other factor.

If you can get the same amount of airflow out of a smaller valve it will tend to make more power easier. So you can see why we feel that the TFS heads flowing about what a very well ported L92 or a factory LS7 with a MUCH smaller valve is easier to make power with, it is less sensitive to cam timing. Basically, as you shove more duration at the TFS heads they tend to make more power, you cannot say that about the big valve heads.

Originally Posted by Brian Tooley

I tend to say mid lift flow is most important on a street/strip car (.300"-.500"), but with the .400" flow number being in the middle, it is easy to say it is the most important, because if you have a killer .400" flow number, the chances are very good that the .300" and .500" are also going to be very good, and that is what makes power. For a race engine you can move that up .100", so the .400"-.600" flow numbers become the most important, and I don't care if you are using 1.000" of cam lift, the mid lift flow is what makes the power.

You have to bear in mind that we have shipped thousands of heads over the years, have been involved in numerous heads up racing organizations, have set probably close to a hundred records and have had dozens of class champions. You can take my cousin Sam Vincent for example, he has been running the same set of Brodix Neal 318 heads from us for 4 years. He just won the Outlaw World Ford Challenge as well as the last NMRA Outlaw race and holds the record. He has a 440 cu in Small block Ford with nitrous on a tiny 28"x10.5" tire, the engine makes over 900 HP on motor with a cast intake and has run 7.40's @ 187 mph on the spray. His heads flow 360 cfm at .500" lift, once again, what I would consider to be the most important flow number for a race engine and right in the middle of his mid lift of .400"-.600" and he does run over 1.000" of intake lift.

The mid lift flow is so much more important than peak flow due to the fact that the cylinder isn't packed with air at the point of peak lift, it is packed with air when the piston is at the bottom of the intake stroke and is coming back up the bore during the compression stroke. This is called volumetric efficiency, ever think about how you can put 110%-120% of atmospheric pressure in a cylinder? Atmospheric pressure is around 14.7 psi, so you would be putting 16-17 psi of pressure into the cylinder! The valve is closing as the piston approaches bottom dead center and the air is still moving forward, then the piston reaches bottom dead center and starts moving up the bore, and the air is still flowing, if you have enough velocity. The SAME amount of airflow around a smaller valve yields MORE velocity. The more airflow that is available at these mid lift points (.300"-.500") the more air is going to continue to pack the cylinder, at some point the pressure in the cylinder overcomes the pressure of the forward moving mass of air, at that point you have intake port reversion. It is at this exact point that you would want to close the intake valve. Smaller intake valves make your low lift flow lower, the lower your low lift flow is (.100"-.200") the lesser your chance of intake reversion. So the smaller intake valves act more like a "check valve" (if you know what that is) to intake port reversion. The lesser your chance of intake reversion, the easier the engine is to cam and is then easier to make power.

So the bottom line is the intake mid lift is MOST IMPORTANT for making power, regardless of intake used or ANY other factor.

If you can get the same amount of airflow out of a smaller valve it will tend to make more power easier. So you can see why we feel that the TFS heads flowing about what a very well ported L92 or a factory LS7 with a MUCH smaller valve is easier to make power with, it is less sensitive to cam timing. Basically, as you shove more duration at the TFS heads they tend to make more power, you cannot say that about the big valve heads.