Square Port heads vs. Cathedral Port heads
10-12-2010, 08:24 PM
#101
TECH Enthusiast
a stock 243 with the same cam,same set up will be pressed to run 120+mph..... you will need more comp, and you will need more duration... aka dick dong cam..... for starters
420-430rwhp tops with an same cam/243 with a manual...............
410-420rwhp tops with an same cam/243 with a auto..........
10-12-2010, 09:10 PM
#102
a stock 243 with the same cam,same set up will be pressed to run 120+mph..... you will need more comp, and you will need more duration... aka dick dong cam..... for starters
420-430rwhp tops with an same cam/243 with a manual...............
410-420rwhp tops with an same cam/243 with a auto..........
420-430rwhp tops with an same cam/243 with a manual...............
410-420rwhp tops with an same cam/243 with a auto..........
10-12-2010, 09:38 PM
#104
459rwhp with stock 243s and the same overlap as your cam. He's running more compression but he's likely also making more power.
https://ls1tech.com/forums/generatio...ls2-heads.html
10-12-2010, 10:10 PM
#105
Understood. And my point was that expensive cathedrals aren't necessary to make the kind of numbers you're talking about.
459rwhp with stock 243s and the same overlap as your cam. He's running more compression but he's likely also making more power.
https://ls1tech.com/forums/generatio...ls2-heads.html
459rwhp with stock 243s and the same overlap as your cam. He's running more compression but he's likely also making more power.
https://ls1tech.com/forums/generatio...ls2-heads.html
Complete Street Performance has been proud to offer this cam for a little over a year now and it has consistently put down great numbers while retaining near stock to stock drivability.
Mike's 2006 GTO M6
-Vararam Intake
-CSP Ported TB
-FAST 102 mm (unported)
-SLP UDP
-Pacsetter Headers
-Borla Exhaust
-Monster Stage 3 Clutch
-And ofcourse the NSSP Cam
459/424
I've been working with Mike and his car from the beginning.
Bolt ons:
With Pacesetter headers and our ported LS2 intake and throttle body he put down 387 rwhp which was right around what everyone else seems to be doing with the same modifications.
Cam and street tune:
Mike installed the NSSP camshaft, the SLP UDP, and an unported FAST 102 after a lot of grumbling of which cam to actually go with, and was hoping to see 410 rwhp.
The car did 447 rwhp at Race Proven Motorsport's dyno off of a street tune I had set up three times in a row. Needless to say he was happy with those numbers! RPM's tuner informed me that the car was pulling up to 4* of timing, which we saw on the street afterwards too. Changed the gas out to Sunoco and the timing retard was gone, but we didn't get a chance to put her back on their dyno.
Dyno Retune:
Skip 2 months later in 50% humidity and high 80s temperature... The owner, Mike, brought his car over to the shop on Saturday to tighten things up on the dyno. On the street tune, he put down 449 rwhp. We tightened the AFR up a little bit more and he put down 451 rwhp. And then we decided to add some timing, upping it from 25* peak to 28-29*. It made 459 rwhp then! We took her out on the street afterwards to verify that it could handle it there, and sure enough it did perfectly.
The NSSP cam is a 230/232 114. It is NOT ground by comp, but the cores are the same cores. It is ground by a local shop to me that has been in the business for over 42 years.
I must tell you, I personally believe it is one of the best cams you can buy, especially dollar for dollar.
Other Cars:
Pete's 2006 GTO M6 made 428 rwhp with the stock unported TB, Intake Manifold, and Crank Pulley. Otherwise we'd expect him to see similar numbers. His car drives like stock.
In my LS3 vette I run a similar cam in my vette with 2* more duration on the exhaust, but the same intake lobe. It put down 501 rwhp. I've put roughly 40,000 miles on my car since I cammed it and it still is holding up very nicely... and it is a daily driver. 2008 Corvette with 68000+ miles haha.
$325 plus shipping!
And $700 plus shipping with springs and pushrods.
Mike's 2006 GTO M6
-Vararam Intake
-CSP Ported TB
-FAST 102 mm (unported)
-SLP UDP
-Pacsetter Headers
-Borla Exhaust
-Monster Stage 3 Clutch
-And ofcourse the NSSP Cam
459/424
I've been working with Mike and his car from the beginning.
Bolt ons:
With Pacesetter headers and our ported LS2 intake and throttle body he put down 387 rwhp which was right around what everyone else seems to be doing with the same modifications.
Cam and street tune:
Mike installed the NSSP camshaft, the SLP UDP, and an unported FAST 102 after a lot of grumbling of which cam to actually go with, and was hoping to see 410 rwhp.
The car did 447 rwhp at Race Proven Motorsport's dyno off of a street tune I had set up three times in a row. Needless to say he was happy with those numbers! RPM's tuner informed me that the car was pulling up to 4* of timing, which we saw on the street afterwards too. Changed the gas out to Sunoco and the timing retard was gone, but we didn't get a chance to put her back on their dyno.
Dyno Retune:
Skip 2 months later in 50% humidity and high 80s temperature... The owner, Mike, brought his car over to the shop on Saturday to tighten things up on the dyno. On the street tune, he put down 449 rwhp. We tightened the AFR up a little bit more and he put down 451 rwhp. And then we decided to add some timing, upping it from 25* peak to 28-29*. It made 459 rwhp then! We took her out on the street afterwards to verify that it could handle it there, and sure enough it did perfectly.
The NSSP cam is a 230/232 114. It is NOT ground by comp, but the cores are the same cores. It is ground by a local shop to me that has been in the business for over 42 years.
I must tell you, I personally believe it is one of the best cams you can buy, especially dollar for dollar.
Other Cars:
Pete's 2006 GTO M6 made 428 rwhp with the stock unported TB, Intake Manifold, and Crank Pulley. Otherwise we'd expect him to see similar numbers. His car drives like stock.
In my LS3 vette I run a similar cam in my vette with 2* more duration on the exhaust, but the same intake lobe. It put down 501 rwhp. I've put roughly 40,000 miles on my car since I cammed it and it still is holding up very nicely... and it is a daily driver. 2008 Corvette with 68000+ miles haha.
$325 plus shipping!
And $700 plus shipping with springs and pushrods.
10-14-2010, 01:25 PM
#110
TECH Enthusiast
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This thread lacks anyone with any sort of fluid dynamics background... Put away your calculators boys. Your geometric port cross section calculations arent going to cut it. There is to much garbage being thrown around this thread.
10-18-2010, 11:21 PM
#112
He makes some good points, but he's way off base on others.
You only need to grasp two basic principles to understand the potential problems with large valve heads.
One: We want the intake air to keep flowing until the intake valve is closed. When does the intake valve close? On my engine it only closes within .050" of seat almost 60 degrees after bottom dead center. THAT MEANS THE PISTON IS 1/3 OF THE WAY BACK UP THE BORE, and it still isn't closed! The piston moving back up the bore tries to push the air back into the intake port.
When does the intake port quit flowing in the forward direction? When the pressure in the cylinder overcomes the incoming velocity of the intake air charge. Obviously you want the valve to close at the same point the intake port quits flowing. The bigger the port and valve, the sooner the valve has to close. The smaller the port and valve, the higher the velocity and the less critical the closing point becomes.
Here is the real math on coefficient of discharge, it's the airflow divided by the curtain area of the valve. (airflow/((valve diameter * pi) * lift) Is the valve at .600" lift when it's almost closed and you're trying to pack the cylinder with air? No, the valve is down in the midlift area. A head with a 2.10" valve flowing 300 cfm at .400" yields 114 cfm per sq in and has more C of D than a 2.165" valve with the same airflow to yeild 110 cfm per sq inch. Large valves generally have LESS midlift flow because of bore shrouding which reduces the midlift flow even further, reducing the C of D and the velocity. Here's the next problem with a large valve. A smaller intake valve acts more like a check valve against intake port reversion at the end of the intake cycle. A bigger intake valve is going to allow the air in the cylinder to flow back up into the intake port easier, hence the big valve being much more sensitive to the close point of the cam timing.
Two: Overscavenging during overlap. Where do we want our intake valve to open and the exhaust to close? Both valves are always open during overlap on our performance LS engines. What we want is the exhaust port to pull just enough clean air into the combustion chamber to clean out the bad gas, and then the exhaust valve to close so the intake stroke can continue. The problem with a large intake valve or exhaust valve is, it tends to pull too much air out during overlap. Larger valves on a 45 degree seat angle (street cars) always flow more air at low lift, this is not what we want. We want low flow at .100"-.150" and then by .300" we want it to flow as much as possible. Too much flow during this low lift overlap period reduces power output because you're blowing it out the exhaust! So heads with bigger valves are more sensitive to cam timing events during overlap. This is specific to engines with long runner intake manifolds, these intakes start acting like restrictor plates on big engines. Install a double throwdown 4 barrel intake, and the overscavenging starts making more torque, and the engine will make plenty of power because the intake has the air to feed it at higher rpms.
I once did a pair of heads for a customer who replaced his $2500 CNC ported LPE LS6 Stg III heads with a pair of TFS 225 heads. He did a data log and it showed the mass airflow was down. He called me upset and I told him to take it to the dyno before he jumped to conclusions. He dyno tested it and picked up 27 rwhp over his expensive ported OEM heads, from 480 rwhp to 507 rwhp. He called me in disbelief as to how he could be down on mass airflow but so far up on power. I explained the over scavenging problem associated with LS engines with long runner intakes and he was a customer for life. He had a LS2 Corvette that on his dyno made within 20 hp of a big dollar LS7 setup. Obviously the LS7 stuff has come a long way since then, guys have figured out the cams.
Don't compare a dry sump engine with titanium rods to a wet sump engine with steel rods, it apples and oranges. I have seen the back to back testing, and it's not pretty. The bottom line is, if you have the cam for the big valve headed combo sorted out, it will do quite fine. Miss it by just a little, and you're looking like an idiot.
Lastly addressing the rant from this uninformed person, rolling the valve from 15 degrees to 13.5 degrees moves the rocker arm and pushrod AWAY from the valve cover giving MORE clearance for those components. A 3/8" pushrod drops right in a TFS head. It also moves the edge of the spring pocket UP for more clearance to the port roof. It also gives about .060" more P to V than the same exact valve in a 15 degree head!
The placement of the intake valve on a LS3 head is quit a bit closer to the cylinder wall than a LS7 head, the combination of this poorer placement and 15 degree valve angle are severe disadvantages to any 13.5 or 12/11 degree head.
Hope this helps.
You only need to grasp two basic principles to understand the potential problems with large valve heads.
One: We want the intake air to keep flowing until the intake valve is closed. When does the intake valve close? On my engine it only closes within .050" of seat almost 60 degrees after bottom dead center. THAT MEANS THE PISTON IS 1/3 OF THE WAY BACK UP THE BORE, and it still isn't closed! The piston moving back up the bore tries to push the air back into the intake port.
When does the intake port quit flowing in the forward direction? When the pressure in the cylinder overcomes the incoming velocity of the intake air charge. Obviously you want the valve to close at the same point the intake port quits flowing. The bigger the port and valve, the sooner the valve has to close. The smaller the port and valve, the higher the velocity and the less critical the closing point becomes.
Here is the real math on coefficient of discharge, it's the airflow divided by the curtain area of the valve. (airflow/((valve diameter * pi) * lift) Is the valve at .600" lift when it's almost closed and you're trying to pack the cylinder with air? No, the valve is down in the midlift area. A head with a 2.10" valve flowing 300 cfm at .400" yields 114 cfm per sq in and has more C of D than a 2.165" valve with the same airflow to yeild 110 cfm per sq inch. Large valves generally have LESS midlift flow because of bore shrouding which reduces the midlift flow even further, reducing the C of D and the velocity. Here's the next problem with a large valve. A smaller intake valve acts more like a check valve against intake port reversion at the end of the intake cycle. A bigger intake valve is going to allow the air in the cylinder to flow back up into the intake port easier, hence the big valve being much more sensitive to the close point of the cam timing.
Two: Overscavenging during overlap. Where do we want our intake valve to open and the exhaust to close? Both valves are always open during overlap on our performance LS engines. What we want is the exhaust port to pull just enough clean air into the combustion chamber to clean out the bad gas, and then the exhaust valve to close so the intake stroke can continue. The problem with a large intake valve or exhaust valve is, it tends to pull too much air out during overlap. Larger valves on a 45 degree seat angle (street cars) always flow more air at low lift, this is not what we want. We want low flow at .100"-.150" and then by .300" we want it to flow as much as possible. Too much flow during this low lift overlap period reduces power output because you're blowing it out the exhaust! So heads with bigger valves are more sensitive to cam timing events during overlap. This is specific to engines with long runner intake manifolds, these intakes start acting like restrictor plates on big engines. Install a double throwdown 4 barrel intake, and the overscavenging starts making more torque, and the engine will make plenty of power because the intake has the air to feed it at higher rpms.
I once did a pair of heads for a customer who replaced his $2500 CNC ported LPE LS6 Stg III heads with a pair of TFS 225 heads. He did a data log and it showed the mass airflow was down. He called me upset and I told him to take it to the dyno before he jumped to conclusions. He dyno tested it and picked up 27 rwhp over his expensive ported OEM heads, from 480 rwhp to 507 rwhp. He called me in disbelief as to how he could be down on mass airflow but so far up on power. I explained the over scavenging problem associated with LS engines with long runner intakes and he was a customer for life. He had a LS2 Corvette that on his dyno made within 20 hp of a big dollar LS7 setup. Obviously the LS7 stuff has come a long way since then, guys have figured out the cams.
Don't compare a dry sump engine with titanium rods to a wet sump engine with steel rods, it apples and oranges. I have seen the back to back testing, and it's not pretty. The bottom line is, if you have the cam for the big valve headed combo sorted out, it will do quite fine. Miss it by just a little, and you're looking like an idiot.
Lastly addressing the rant from this uninformed person, rolling the valve from 15 degrees to 13.5 degrees moves the rocker arm and pushrod AWAY from the valve cover giving MORE clearance for those components. A 3/8" pushrod drops right in a TFS head. It also moves the edge of the spring pocket UP for more clearance to the port roof. It also gives about .060" more P to V than the same exact valve in a 15 degree head!
The placement of the intake valve on a LS3 head is quit a bit closer to the cylinder wall than a LS7 head, the combination of this poorer placement and 15 degree valve angle are severe disadvantages to any 13.5 or 12/11 degree head.
Hope this helps.
10-19-2010, 10:57 AM
#113
He did a data log and it showed the mass airflow was down. He called me upset and I told him to take it to the dyno before he jumped to conclusions. He dyno tested it and picked up 27 rwhp over his expensive ported OEM heads, from 480 rwhp to 507 rwhp. He called me in disbelief as to how he could be down on mass airflow but so far up on power.
The whole thing is simple. Flow air period.
Anyways informative thread indeed
10-20-2010, 10:29 AM
#114
FormerVendor
One fact being forgotten is that most all of these heads can fill the cubes they are feeding to 7K or so and with that being said they will all make similar numbers. They will just require different cams. The bigger heads can run a smaller camshaft on intake for the same powerband in general and we do it all the time.
If I have a 440 inch LSx and I turn it 6500 it should make X hp and X tq based on its size and rpm and VE and these different heads can and will make nearly the same numbers including the cathedral and the square port heads.
If I want to turn that same 440 LSx to 8000+ rpm then the square ports with a good carb style manifold will start making more power due to their larger size and airflow potential as long as the manifold also works in that range.
Also like the knowledgable square port guys already know the bigger valved LS3 / LS7 heads are a little more picky on cams as Brian said as well which seems to be true. I like the square ports on bigger engines and they run well and the Cathedrals run well on everything it seems since there are some very small ones to very large ones.
Also as has been said the peripherals are also a major player as to what is and is not making power on these different heads as there are many different intake manifolds for each that can not be used on the other.
All else being equal it's good in general to have raised ports etc. so no ones denying that as far as I see. I think this discussion is half about the ports shapes and maybe even more than half about the relative sizes of these heads vs the cams and intakes that they all run.
We need a few recipes for similar (but truly observed) hp and tq at a certain CID between these different headed combos with what real cams they have and then people can make some decisions. We use both styles of these heads a lot and can make a lot of power with both.
If I have a 440 inch LSx and I turn it 6500 it should make X hp and X tq based on its size and rpm and VE and these different heads can and will make nearly the same numbers including the cathedral and the square port heads.
If I want to turn that same 440 LSx to 8000+ rpm then the square ports with a good carb style manifold will start making more power due to their larger size and airflow potential as long as the manifold also works in that range.
Also like the knowledgable square port guys already know the bigger valved LS3 / LS7 heads are a little more picky on cams as Brian said as well which seems to be true. I like the square ports on bigger engines and they run well and the Cathedrals run well on everything it seems since there are some very small ones to very large ones.
Also as has been said the peripherals are also a major player as to what is and is not making power on these different heads as there are many different intake manifolds for each that can not be used on the other.
All else being equal it's good in general to have raised ports etc. so no ones denying that as far as I see. I think this discussion is half about the ports shapes and maybe even more than half about the relative sizes of these heads vs the cams and intakes that they all run.
We need a few recipes for similar (but truly observed) hp and tq at a certain CID between these different headed combos with what real cams they have and then people can make some decisions. We use both styles of these heads a lot and can make a lot of power with both.
10-20-2010, 01:58 PM
#115
Check out the head comparison in the new Hod Rod mag. It shows what a lot of us already knew...good heads are all very close in power production...this includes the square port heads. This is also why very few head swaps are just that; when someone is trumpeting their brand of heads. What I mean is the head swap always involves thinner gaskets, higher compression, port matched intakes, larger intakes, larger throttle bodies, better intake tracts-filters, steeper intake valve seat angle, better exhaust, different camshaft, bore matched chambers, lighter thinner headed valves, better valvesprings, pushrods, rocker arms, etc. The reason this arguement is so good is that everyone is mostly right. So get the most bang for your buck on heads suitable for your application and optimize everything else...cause "everything else" will get you a lot more hp than the heads themselves. (I know that I am an opinionated old guy)
10-20-2010, 02:27 PM
#116
FormerVendor
The reason this arguement is so good is that everyone is mostly right. So get the most bang for your buck on heads suitable for your application and optimize everything else...cause "everything else" will get you a lot more hp than the heads themselves. (I know that I am an opinionated old guy)
10-20-2010, 02:50 PM
#117
TECH Fanatic
He makes some good points, but he's way off base on others.
You only need to grasp two basic principles to understand the potential problems with large valve heads.
One: We want the intake air to keep flowing until the intake valve is closed. When does the intake valve close? On my engine it only closes within .050" of seat almost 60 degrees after bottom dead center. THAT MEANS THE PISTON IS 1/3 OF THE WAY BACK UP THE BORE, and it still isn't closed! The piston moving back up the bore tries to push the air back into the intake port.
When does the intake port quit flowing in the forward direction? When the pressure in the cylinder overcomes the incoming velocity of the intake air charge. Obviously you want the valve to close at the same point the intake port quits flowing. The bigger the port and valve, the sooner the valve has to close. The smaller the port and valve, the higher the velocity and the less critical the closing point becomes.
Here is the real math on coefficient of discharge, it's the airflow divided by the curtain area of the valve. (airflow/((valve diameter * pi) * lift) Is the valve at .600" lift when it's almost closed and you're trying to pack the cylinder with air? No, the valve is down in the midlift area. A head with a 2.10" valve flowing 300 cfm at .400" yields 114 cfm per sq in and has more C of D than a 2.165" valve with the same airflow to yeild 110 cfm per sq inch. Large valves generally have LESS midlift flow because of bore shrouding which reduces the midlift flow even further, reducing the C of D and the velocity. Here's the next problem with a large valve. A smaller intake valve acts more like a check valve against intake port reversion at the end of the intake cycle. A bigger intake valve is going to allow the air in the cylinder to flow back up into the intake port easier, hence the big valve being much more sensitive to the close point of the cam timing.
...
The placement of the intake valve on a LS3 head is quit a bit closer to the cylinder wall than a LS7 head, the combination of this poorer placement and 15 degree valve angle are severe disadvantages to any 13.5 or 12/11 degree head.
Hope this helps.
You only need to grasp two basic principles to understand the potential problems with large valve heads.
One: We want the intake air to keep flowing until the intake valve is closed. When does the intake valve close? On my engine it only closes within .050" of seat almost 60 degrees after bottom dead center. THAT MEANS THE PISTON IS 1/3 OF THE WAY BACK UP THE BORE, and it still isn't closed! The piston moving back up the bore tries to push the air back into the intake port.
When does the intake port quit flowing in the forward direction? When the pressure in the cylinder overcomes the incoming velocity of the intake air charge. Obviously you want the valve to close at the same point the intake port quits flowing. The bigger the port and valve, the sooner the valve has to close. The smaller the port and valve, the higher the velocity and the less critical the closing point becomes.
Here is the real math on coefficient of discharge, it's the airflow divided by the curtain area of the valve. (airflow/((valve diameter * pi) * lift) Is the valve at .600" lift when it's almost closed and you're trying to pack the cylinder with air? No, the valve is down in the midlift area. A head with a 2.10" valve flowing 300 cfm at .400" yields 114 cfm per sq in and has more C of D than a 2.165" valve with the same airflow to yeild 110 cfm per sq inch. Large valves generally have LESS midlift flow because of bore shrouding which reduces the midlift flow even further, reducing the C of D and the velocity. Here's the next problem with a large valve. A smaller intake valve acts more like a check valve against intake port reversion at the end of the intake cycle. A bigger intake valve is going to allow the air in the cylinder to flow back up into the intake port easier, hence the big valve being much more sensitive to the close point of the cam timing.
...
The placement of the intake valve on a LS3 head is quit a bit closer to the cylinder wall than a LS7 head, the combination of this poorer placement and 15 degree valve angle are severe disadvantages to any 13.5 or 12/11 degree head.
Hope this helps.
Brian,
Didn't you mean "when the cylinder pressure becomes higher than the intake port pressure (not the velocity)?" Any airmass moves due to pressure differential (delta p). So, as long as port pressure exceeds cylinder pressure (no mater where the piston is and what direction it is moving), airmass will flow from the higher (port) pressure area to the lower pressure area (cylinder).
As you mentioned, it would be useful to close the intake valve when delta p = zero.
As the intake valve nears it's seat the curtain area is decreasing and, with a positive delta p (port/cylinder) the charge velocity is increasing. We know what happens to pressure when velocity increases.
With correct intake tuning lengths and valve events, a considerable mass of air can be pumped into the cylinder near IVC. Let's say there is a 3 psi delta p when the valve is about 0.050 from closed in a well designed intake system. That's about 83 in. H2O, so a substantial mass of air will be passing thru the curtain area. Perhaps, just perhaps, the larger curtain area of a bigger valve will allow more airmass to pass in the final stages of the intake valve closing.
3 psi delta p is not unreasonable; some NA engines see nearer 5 psi approaching IVC. 28 in. H2O is about equal to 1.0 psi. Very folks look at flow in the 80-130 in. H2O area. Well, some probably do.
Hope this helps.
Jon
Another OOG (very Old and very Opinionated)
10-20-2010, 09:32 PM
#118
TECH Enthusiast
Two: Overscavenging during overlap. Where do we want our intake valve to open and the exhaust to close? Both valves are always open during overlap on our performance LS engines. What we want is the exhaust port to pull just enough clean air into the combustion chamber to clean out the bad gas, and then the exhaust valve to close so the intake stroke can continue. The problem with a large intake valve or exhaust valve is, it tends to pull too much air out during overlap. Larger valves on a 45 degree seat angle (street cars) always flow more air at low lift, this is not what we want. We want low flow at .100"-.150" and then by .300" we want it to flow as much as possible. Too much flow during this low lift overlap period reduces power output because you're blowing it out the exhaust! So heads with bigger valves are more sensitive to cam timing events during overlap .
The issue of pulling too much air: Is not correct... The issue you have with large port, large valve and overlap is when you have a condition when too much overlap exist, and the time both valves are open some residual exhaust gases can disrupt the intake charge and seek the path of the intake port ie especially at low rpms.... Exhaust reversion condition
10-21-2010, 09:28 AM
#120
Not quite bro...... You use overlap to help increase the inhertia of the fresh air intake charge....... Not to cleanout the cylinder of exhaust gases....
The issue of pulling too much air: Is not correct... The issue you have with large port, large valve and overlap is when you have a condition when too much overlap exist, and the time both valves are open some residual exhaust gases can disrupt the intake charge and seek the path of the intake port ie especially at low rpms.... Exhaust reversion condition
The issue of pulling too much air: Is not correct... The issue you have with large port, large valve and overlap is when you have a condition when too much overlap exist, and the time both valves are open some residual exhaust gases can disrupt the intake charge and seek the path of the intake port ie especially at low rpms.... Exhaust reversion condition