Square Port heads vs. Cathedral Port heads
10-06-2010, 09:29 AM
#1
Square Port heads vs. Cathedral Port heads There's been a lot of talk lately about GM's square port heads versus the Cathedral Port heads we've all become familiar with. Frankly the majority here seem to frown upon the Square Port stuff for a variety of reasons, many of which are based on false information. Here's a very good read I came across to shed some light on reality. The math here is the interesting part since it's hard to argue with numbers. Enjoy.
http://www.afdracing.com/square%20po...sx%20heads.doc
http://www.afdracing.com/square%20po...sx%20heads.doc
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BennyB (10-19-2020)
10-06-2010, 09:47 AM
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Very interesting read, thank you for sharing it. This is exactly the kind of information I had been wondering about and was looking for in the thread I started a week or two ago.
10-06-2010, 11:21 AM
#4
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Yelp, this was posted on speedtalk last night..... I have been saying this, and certain marketers have marketed so much propaganda......
Here is are some snippets that were interesting from -Dennis Wheet Jr
If you still believe in global warning too, just get ready when they make you start paying the carbon tax..... marketing and propaganda..... Too many sheep and sheep are lead by shepards and sometimes wolves..
Reasonable men adapt to the world around them, unreasonable men expect the world to adapt to them, therefore all change is made by unreasonable men....... correlate this to life how its applicable......
Bozz
Here is are some snippets that were interesting from -Dennis Wheet Jr
Au contraire mon frere
Let’s come back to our friend MATH again. We will be working with him through the rest of the document so be nice to him and he will be nice to you. I promise we will keep it at a grade school level though. Before we get there we need to agree on a few things.
Everyone's flow bench is different (or so the aftermarket wants you to believe). So we need to agree on some flow numbers for this experiment.
1. Average ported LS6 heads (or copies) w/ a 2.055 valve (Most I see carry a 91% throat and flow around 320 cfm peak).
2. Average ported LS3 heads (or copies) w/ a 2.165 valve (Most carry the same 91% throat and flow around 365 cfm peak).
It stands to reason if we can figure out the area of the throat and compare it to the amount of airflow we can get a quick down and dirty idea of which cylinder head is “faster” in airspeed.
LS6 head to start.
2.055 * .91 = 1.870 throat diameter
A simple formula for finding the area of a circle is (diameter x diameter x .7854)
So, 1.870 x 1.870 x .7854 = 2.746 “sq. of throat area.
Then 320 cfm/2.746 “sq. = 116.53 cfm/sq” of throat area.
Now I am not going to bore you with the math the whole way through this, so get your calculator and see if you find the same results as I do!
LS3 (big fat and slow...right?)
365 cfm for every 3.046”sq of area, or more simply, there is 119.83 cfm/sq” of throat area. Much slower....WAIT! HOLD ON. More cfm / sq” = higher velocity. If we move more air through the same size hole the only way we can do it is by moving it FASTER!
So much for that big ugly port being slow. Now what does all this mean? And why are people lying to me? Read on:
2. Big velocity / Low lift flow builds big TQ. (Cathedral ports are for velocity)
(or...Brawndo has what plants crave...electrolytes)
Mass marketing's purpose is simple: Scare the consumer into spending money. Turn on your TV and think about what someone is trying to sell you. “You need to get rid of your earth killing incandescent light bulbs and purchase compact fluorescent bulbs (that contain mercury) as they are safer and conserve electricity”. Think about that for a moment.
This is where you are going to think that I am going to start sounding like Mr. Beck. Honestly... I don't howl at the moon... I don't attend tea parties nor believe in conspiracy theories. But facts are facts. Marketing has won over truth for many years. Who invented the radio? Marconi? Think again! Mass marketing even made its way into your history book in school! I don't honestly believe all marketing is bad. But let’s remember what the purpose of marketing is. The people doing the marketing want to get the pictures of the dead Presidents out of your wallet. A white lie here or there won't hurt anyone right ?
At the current point in time most of the aftermarket cylinder head companies have large investments in the castings that are on there shelves. Core box cost, foundry time, etc. etc. Big bad GM comes by and throws a bucket of water on the fire with the square port head. What to do? Remember... a little white lie can't hurt anyone right?
It looks BIG.. Let’s tell them it is TOO BIG to make TQ. It will be some big fat lethargic heap. The real small cathedral port head will make BIG TQ. Small ports and smaller headers MAKE BIG TQ! Yeah, RIGHT! If we keep this up Bernoulli is going to climb out of his grave.- Dennis Wheet Jr.
Let’s come back to our friend MATH again. We will be working with him through the rest of the document so be nice to him and he will be nice to you. I promise we will keep it at a grade school level though. Before we get there we need to agree on a few things.
Everyone's flow bench is different (or so the aftermarket wants you to believe). So we need to agree on some flow numbers for this experiment.
1. Average ported LS6 heads (or copies) w/ a 2.055 valve (Most I see carry a 91% throat and flow around 320 cfm peak).
2. Average ported LS3 heads (or copies) w/ a 2.165 valve (Most carry the same 91% throat and flow around 365 cfm peak).
It stands to reason if we can figure out the area of the throat and compare it to the amount of airflow we can get a quick down and dirty idea of which cylinder head is “faster” in airspeed.
LS6 head to start.
2.055 * .91 = 1.870 throat diameter
A simple formula for finding the area of a circle is (diameter x diameter x .7854)
So, 1.870 x 1.870 x .7854 = 2.746 “sq. of throat area.
Then 320 cfm/2.746 “sq. = 116.53 cfm/sq” of throat area.
Now I am not going to bore you with the math the whole way through this, so get your calculator and see if you find the same results as I do!
LS3 (big fat and slow...right?)
365 cfm for every 3.046”sq of area, or more simply, there is 119.83 cfm/sq” of throat area. Much slower....WAIT! HOLD ON. More cfm / sq” = higher velocity. If we move more air through the same size hole the only way we can do it is by moving it FASTER!
So much for that big ugly port being slow. Now what does all this mean? And why are people lying to me? Read on:
2. Big velocity / Low lift flow builds big TQ. (Cathedral ports are for velocity)
(or...Brawndo has what plants crave...electrolytes)
Mass marketing's purpose is simple: Scare the consumer into spending money. Turn on your TV and think about what someone is trying to sell you. “You need to get rid of your earth killing incandescent light bulbs and purchase compact fluorescent bulbs (that contain mercury) as they are safer and conserve electricity”. Think about that for a moment.
This is where you are going to think that I am going to start sounding like Mr. Beck. Honestly... I don't howl at the moon... I don't attend tea parties nor believe in conspiracy theories. But facts are facts. Marketing has won over truth for many years. Who invented the radio? Marconi? Think again! Mass marketing even made its way into your history book in school! I don't honestly believe all marketing is bad. But let’s remember what the purpose of marketing is. The people doing the marketing want to get the pictures of the dead Presidents out of your wallet. A white lie here or there won't hurt anyone right ?
At the current point in time most of the aftermarket cylinder head companies have large investments in the castings that are on there shelves. Core box cost, foundry time, etc. etc. Big bad GM comes by and throws a bucket of water on the fire with the square port head. What to do? Remember... a little white lie can't hurt anyone right?
It looks BIG.. Let’s tell them it is TOO BIG to make TQ. It will be some big fat lethargic heap. The real small cathedral port head will make BIG TQ. Small ports and smaller headers MAKE BIG TQ! Yeah, RIGHT! If we keep this up Bernoulli is going to climb out of his grave.- Dennis Wheet Jr.
But what happens when the port isn't big enough? Why wouldn't it be big enough? 3 words... Corvettes and Pickup Trucks. GM's flagship car the Corvette must run really well. GM's number one seller, the trucks must also run well. New casting technologies allowed GM to produce a new style of cylinder head at a price point like no other. Less than $150 cost per head! This allowed more cost to be applied in other places (read offset rockers and additional vehicle engineering) The L92/L76/LS3 cylinder head was born.
If we compare the original LQ series 6.0l truck to the new L92 / L94 (square port) engine we see TQ output is up roughly 12% yet the new engine is only 3% larger? Obviously the square port head does a pretty good job of making power in short order! Remember our friend MATH? -Dennis Wheet Jr
If we compare the original LQ series 6.0l truck to the new L92 / L94 (square port) engine we see TQ output is up roughly 12% yet the new engine is only 3% larger? Obviously the square port head does a pretty good job of making power in short order! Remember our friend MATH? -Dennis Wheet Jr
Reasonable men adapt to the world around them, unreasonable men expect the world to adapt to them, therefore all change is made by unreasonable men....... correlate this to life how its applicable......
Bozz
10-06-2010, 11:40 AM
#5
I see alot of dyno graphs and threads on this board boasting big catheral port power numbers on Big CI engines, saying they will make more under the curve power then a properly setup ls7 style head.... me personally i have never seen it on my dyno, they may make more power slightly below 3500, but above that from my experience they get crushed by a properly setup ls7 setup..... i mean lets put dyno numbers aside, look at the these c6 z06 vettes, these cars are going 133-138 in the quarter with a too tall of gearing, mildish cam and long tubes, that is unheard of back a few years back with a similar sized motor , catheral ports, and much larger camshafts
10-06-2010, 01:02 PM
#7
TECH Enthusiast
I also want them to show proof that they make more avg tq from idle-4500....
Last edited by bozzhawg; 10-06-2010 at 01:16 PM.
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10-06-2010, 02:25 PM
#8
When the LS1 debuted all the LT1 and traditional SBC guys crapped all over it as well ( Some still do )
The whole thing is simple. Flow air period.
More air and more efficient BTU extraction will = more power and thats really all there is to it. Theres no black magic here. The LS3/L92 head flows more air in stock trim than most aftermarket CNC cathedrals do.
Granted the cathedrals have had ten plus years of R&D and trial and error with cam selections and whatnot so maybe its "easier" to hit hp goals more consistently now with cathedral head builds but so what? Lots of guys are doing very well with the LS3 head and it will only get better IMO
Wait until everyone masters VVT tuning LOL
The whole thing is simple. Flow air period.
More air and more efficient BTU extraction will = more power and thats really all there is to it. Theres no black magic here. The LS3/L92 head flows more air in stock trim than most aftermarket CNC cathedrals do.
Granted the cathedrals have had ten plus years of R&D and trial and error with cam selections and whatnot so maybe its "easier" to hit hp goals more consistently now with cathedral head builds but so what? Lots of guys are doing very well with the LS3 head and it will only get better IMO
Wait until everyone masters VVT tuning LOL
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Racer86 (10-28-2020)
10-06-2010, 03:49 PM
#10
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sigh...
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
10-06-2010, 04:24 PM
#11
sigh...
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
There are plenty of 6.0L GTO's using l92's, stock or ported with cams making as good or more power than cathedral port setups.
LS3's with headers and a cold air intake make as much power and more torque than many cam only and even some heads/cam ls1 setups. Can you truly say the heads have nothing to do with that?
GM's truck lineup now uses square ports heads and these motors make more hp and torque than in the past, plus get better fuel mileage.
Gaining 110rwhp on a heads/cam/intake package isn't really anything new. People were seeing those gains since the early 2000's on some of the better setups so I don't see how that takes away from square port heads. Not to mention that's comparing a stock gm casting to an aftermarket head that had additional work done to it beyond how it comes out of the box. If they ported the l92's then pulled them for cathedral ports and picked up a significant amount of power then you could use that as an arguement but that wasn't the case.
I'm keeping this discussion oriented rather than arguementative, I'm just responding to some points you made so please take it as such.
10-06-2010, 04:31 PM
#12
TECH Enthusiast
sigh...
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
We have seen the test of AFR vs L92's and the cheap, slow flow heads outperformed the $2500 head period.....
Click here for an unbiased test below..... what happened to the AFR?
http://www.gmhightechperformance.com...h/results.html
from idle-4500 the L92 made more torque, but its marketed that the L92's do not make torque down low, port too big....lol You have been told and marketed across every blog board that the ports are too big to make lowend torque..... Bull
The bottomline the L92's work period do not be a sheep and fall for the marketing......
A better comparison would be a L92 vs Mast rect port head...
Or compare the AFR 230v2 vs another aftermarket head in the same class Trickflow, Dart, PI, etc....
Last edited by bozzhawg; 10-06-2010 at 04:42 PM.
10-06-2010, 04:48 PM
#13
I may have been one of the first to use the L92 heads and have continued to use them. FIrst on my 403 and now on my 427. Cammed correctly, I've always made great average power with absurd tip in. I still haven't found a reason to move away from them.
I was talking with Shawn at VA Speed last weekend. He wishes he could find a way to make people understand how mild my car really is.
I was talking with Shawn at VA Speed last weekend. He wishes he could find a way to make people understand how mild my car really is.
10-06-2010, 04:49 PM
#14
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Click here for an unbiased test below..... what happened to the AFR?
http://www.gmhightechperformance.com...h/results.html
from idle-4500 the L92 made more torque,
http://www.gmhightechperformance.com...h/results.html
from idle-4500 the L92 made more torque,
Looks like the AFR made more torque and power from 3300-4700 than the L92.
You need to quit posting up false statements or at least post some data that make your statement true. "from idle-4500 the L92 made more torque". becasue that table of data sure doesn't back it up.
10-06-2010, 05:06 PM
#15
TECH Enthusiast
Looks like the AFR made more torque and power from 3300-4700 than the L92.
You need to quit posting up false statements or at least post some data that make your statement true. "from idle-4500 the L92 made more torque". becasue that table of data sure doesn't back it up.
You need to quit posting up false statements or at least post some data that make your statement true. "from idle-4500 the L92 made more torque". becasue that table of data sure doesn't back it up.
L92 485=avg torque AFR225=482 avg torque...... small difference right, I only bring this up because when some state a case, they use the smallest numbers but magnify it in marketing...
Also from 4750-6250 who made more torque as well?
It seems like the cathedral ports and aftermarket (we know who) is promoted here big time.... funny anytime someone does not agree with you they get trashed.... example Spinmonster... Good guy, not along with the pack or the in crowd and was not a sheep....
99 Aggie I am not trying to go back in forth with you, you and I are prob not going to change each others minds anyway, but I ask you one question:
Can you admit on LS1tech that the L92 out performed the AFR 225 in this test?
Last edited by bozzhawg; 10-06-2010 at 05:36 PM.
10-06-2010, 05:33 PM
#16
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Well the L92's needed 260cc runners and bigger valves to match/slightly beat the 225cc afr heads. Would be interesting to see the dyno comparison of the mast small square port heads. They have a 15cc smaller intake runner than the l92s and flows slightly better.
10-06-2010, 05:36 PM
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wish they would have started the pull at a lower rpm - since the graph only goes to 3000.
So your saying the bigger higher flowing head barely out performed the smaller 225 head?
Depending on the engine build each head has it's place where it is going to make best power.
So your saying the bigger higher flowing head barely out performed the smaller 225 head?
Depending on the engine build each head has it's place where it is going to make best power.
10-06-2010, 05:44 PM
#18
TECH Enthusiast
wish they would have started the pull at a lower rpm - since the graph only goes to 3000.
So your saying the bigger higher flowing head barely out performed the smaller 225 head?
Depending on the engine build each head has it's place where it is going to make best power.
So your saying the bigger higher flowing head barely out performed the smaller 225 head?
Depending on the engine build each head has it's place where it is going to make best power.
10-06-2010, 05:56 PM
#19
sigh...
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
They are awesome for a stock head. People are to caught up in flow numbers. They see 330cfm from a stock head and automaticly think it was touched by god himself. 330cfm from a 260cc intake runner isn't great. Of couse it flow that much with that big of a runner. Now a 215 or 230 head that flows that is much more impressive but still doesn't mean dog ****. Again everyone is to caught up in flow numbers and while they are great to look at they dont always trasnfer into real world results, much like this article square ports work great on papper but in the real world not what its cracked up to be. Sure a properly done ls7 head is awesome but I think most normal people will use the l92/ls3 head. The l92 head has drawbacks, specificly ptv issues. Pat g gained nearly 110rwhp droping l92's in favor of new afr heads, fast and cam.
And this was exactly what the article was refering to when it stated how people are drawn in by marketing, and what really is the deal..... I hate to say it, but what are both of your backgrounds on airflow? Im assuming not anything more than reading ls1 tech sponsors opinions.....
I think it was a great article, and it makes some sense of the numbers, really it also shows why NOT to take everything you read on tech for gospel.....
10-06-2010, 06:01 PM
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Nice read! Thanks. I have a few questions though. One, related to the statement "If we compare the original LQ series 6.0l truck to the new L92 / L94 (square port) engine we see TQ output is up roughly 12% yet the new engine is only 3% larger? Obviously the square port head does a pretty good job of making power in short order!"
For the 12% increase in power for the 3% size increase, is this normally a linear increase? For example a ~3% increase in size with the same heads, what would the normal power gain be?
For the 12% increase in power for the 3% size increase, is this normally a linear increase? For example a ~3% increase in size with the same heads, what would the normal power gain be?