Square Port heads vs. Cathedral Port heads
Staging Lane
Joined: Aug 2007
Posts: 80
Likes: 0
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.
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.....
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.....
On The Tree
Joined: Jun 2010
Posts: 123
Likes: 0
L92's have 260cc runners. Simple physics, smaller runners create more bottom end, bigger runners create less bottom end, and not always at WOT but cruise and part-throttle. Same applies to intake manifolds. High flowing heads are gonna make more PEAK torque(and at a higher RPM), with a peaky powerband, and of course the topend HP. If a smaller CC head flows the same or close to the same as a bigger port head then the smaller port head is SUPERIOR. Not much proof that a L92 makes more torque.
On The Tree
Joined: Oct 2003
Posts: 150
Likes: 0
From: harrisburg PA
L92's have 260cc runners. Simple physics, smaller runners create more bottom end, bigger runners create less bottom end, and not always at WOT but cruise and part-throttle. Same applies to intake manifolds. High flowing heads are gonna make more PEAK torque(and at a higher RPM), with a peaky powerband, and of course the topend HP. If a smaller CC head flows the same or close to the same as a bigger port head then the smaller port head is SUPERIOR. Not much proof that a L92 makes more torque.
Smaller runners create more bottom end? "Simple Fixes"?
Tell me more!
Not to take anything away from Dennis (AirflowDevelop), but I believe there are some variable that are overlooked in his article. If you attempt to draw the comparison he does, then a huge head with increasingly high flow numbers will produce the "FASTER" port as he calls it every time. The problem is, you have to produce the air speed. If you have a small engine (smaller bore/stroke) under the larger port, you need more engine speed to pull the same velocity as you would on a larger engine. All I am saying is maybe on a small engine, the smaller cathedral ports would work better.
TECH Enthusiast
Joined: Jan 2010
Posts: 578
Likes: 4
From: REALITY
L92's have 260cc runners. Simple physics, smaller runners create more bottom end, bigger runners create less bottom end, and not always at WOT but cruise and part-throttle. Same applies to intake manifolds. High flowing heads are gonna make more PEAK torque(and at a higher RPM), with a peaky powerband, and of course the topend HP. If a smaller CC head flows the same or close to the same as a bigger port head then the smaller port head is SUPERIOR. Not much proof that a L92 makes more torque.
And also explain why more torque is built....
thx
I think the author hit the nail on the head when he said that marketing has won over truth for many years. I know Ive only been involved in hot rods for 3 years but Ive bought many a product due to marketing that turned out to be bogus hokus pocus . It seems that there are quite a few products in this industry that over-promise but under deliver, and a few companies have figured out that the dyno figures are one of the best tools that can be used in marketing.
very good article.
very good article.
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Matching port velocity to the displacement of the short block is one of several reasons why GM continues to use the cathedral port head on the smaller 4.8L and 5.3L engines. The smaller 3.78" bores also shroud the 2.0" valves of the 243 and 799 heads much less than they would the 2.165" intake valves on the L92 heads. This is another reason why the General still uses the venerable cathedral port head on over 80% of their trucks sold worldwide.
When you're talking rectangular port heads, the LS7 head is vastly superior to the L92 head in stock and modified form. This is why you see so many 427s with LS7 heads making 570rwhp and greater and you see so few L92 headed 427s getting above the 530s. Both have similar port size and valve size. The LS7 head is just a much more developed piece. This is the big reason why GM ditched the L92 project and went with the LS7 heads for the C6 Z06. It was impossible for them to achieve their power and emissions goals with the earlier head.
When you're talking rectangular port heads, the LS7 head is vastly superior to the L92 head in stock and modified form. This is why you see so many 427s with LS7 heads making 570rwhp and greater and you see so few L92 headed 427s getting above the 530s. Both have similar port size and valve size. The LS7 head is just a much more developed piece. This is the big reason why GM ditched the L92 project and went with the LS7 heads for the C6 Z06. It was impossible for them to achieve their power and emissions goals with the earlier head.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Question for the L92 guru's posting. What L92 casting is bad about cracking, heard it was under on of the intake or exhaust spring perches. Think 2 or 3 people have had this happen already.
TECH Enthusiast
Joined: Jan 2010
Posts: 578
Likes: 4
From: REALITY
Matching port velocity to the displacement of the short block is one of several reasons why GM continues to use the cathedral port head on the smaller 4.8L and 5.3L engines. The smaller 3.78" bores also shroud the 2.0" valves of the 243 and 799 heads much less than they would the 2.165" intake valves on the L92 heads. This is another reason why the General still uses the venerable cathedral port head on over 80% of their trucks sold worldwide.
When you're talking rectangular port heads, the LS7 head is vastly superior to the L92 head in stock and modified form. This is why you see so many 427s with LS7 heads making 570rwhp and greater and you see so few L92 headed 427s getting above the 530s. Both have similar port size and valve size. The LS7 head is just a much more developed piece. This is the big reason why GM ditched the L92 project and went with the LS7 heads for the C6 Z06. It was impossible for them to achieve their power and emissions goals with the earlier head.
When you're talking rectangular port heads, the LS7 head is vastly superior to the L92 head in stock and modified form. This is why you see so many 427s with LS7 heads making 570rwhp and greater and you see so few L92 headed 427s getting above the 530s. Both have similar port size and valve size. The LS7 head is just a much more developed piece. This is the big reason why GM ditched the L92 project and went with the LS7 heads for the C6 Z06. It was impossible for them to achieve their power and emissions goals with the earlier head.
and the next question would be why would anyone put a L92 head on a 427 when they could use a LS7 head?
But now all 6.0+ trucks have the rec port heads..... The new GM trucks, Silverado,GMC, etc.. now offer a 6.2 L92...... LY6 and L92's .....now if they are so lackluster in torque, I doubt GM would continue to use them especially in heavy duty applications..... Sounds like yall want the ol 8.1 cathedral port headed back....lol
You ve seen the commercials, the truck pulling a ship or airplane, rock, or concrete beams at the construction site......lol and What is this called.....PROPAGANDA AND MARKETING.....
Its coming Pat.....its coming haus..... don't fight the feeling....
jeffreycastgsx: comeback to the discussion bro, I am waiting on the physics.........
But now all 6.0+ trucks have the rec port heads..... The new GM trucks, Silverado,GMC, etc.. now offer a 6.2 L92...... LY6 and L92's .....now if they are so lackluster in torque, I doubt GM would continue to use them especially in heavy duty applications..... Sounds like yall want the ol 8.1 cathedral port headed back....lol
The thing that saves them are the small cams and variable valve timing that GM blesses them with. My 5.3L Suburban with the A4 trans would run circles around my 6.2L Denali with the A6 until I tuned it. Variable valve timing (when done for power and not fuel economy) is a godsend on these L92 truck motors. They are so dang lazy down low it's not even funny. I love VVT. It's so much fun to play with the cam phasing, even on the 5.3L engines. Really wakes them up. Anyway, I expect that General Motors will come out with a smaller scale rectangular port head for the small bore 4.8 and 5.3 engines now that Ford has stepped up their game with the new Hurricane engines (which are very badass 2 valve engines by the way).
Keep in mind, I like the L92 heads. You can call me a fan. But I'm more loyal to horsepower and if another head makes more power, it has my attention. I am a power junkie and I will continue to explore power opportunities as they develop.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
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?
On The Tree
Joined: Oct 2003
Posts: 150
Likes: 0
From: harrisburg PA
I don't know if you own a truck with L92 heads, but I do. And I've tuned dozens of them. Remember, I live in Truckville. The thing that saves them are the small cams and variable valve timing that GM blesses them with.
My 5.3L Suburban with the A4 trans would run circles around my 6.2L Denali with the A6 until I tuned it. Variable valve timing (when done for power and not fuel economy) is a godsend on these L92 truck motors. They are so dang lazy down low it's not even funny. I love VVT. It's so much fun to play with the cam phasing, even on the 5.3L engines. Really wakes them up. Anyway, I expect that General Motors will come out with a smaller scale rectangular port head for the small bore 4.8 and 5.3 engines now that Ford has stepped up their game with the new Hurricane engines (which are very badass 2 valve engines by the way).
Keep in mind, I like the L92 heads. You can call me a fan. But I'm more loyal to horsepower and if another head makes more power, it has my attention. I am a power junkie and I will continue to explore power opportunities as they develop.
The thing that saves them are the small cams and variable valve timing that GM blesses them with. My 5.3L Suburban with the A4 trans would run circles around my 6.2L Denali with the A6 until I tuned it. Variable valve timing (when done for power and not fuel economy) is a godsend on these L92 truck motors. They are so dang lazy down low it's not even funny. I love VVT. It's so much fun to play with the cam phasing, even on the 5.3L engines. Really wakes them up. Anyway, I expect that General Motors will come out with a smaller scale rectangular port head for the small bore 4.8 and 5.3 engines now that Ford has stepped up their game with the new Hurricane engines (which are very badass 2 valve engines by the way).
Keep in mind, I like the L92 heads. You can call me a fan. But I'm more loyal to horsepower and if another head makes more power, it has my attention. I am a power junkie and I will continue to explore power opportunities as they develop.
Or that GM will come out with a scaled down rectangular port head for smaller bore/displacement engines?
Or that the Ford Hurricane 6.2L is a badass engine?
I'd put money on any of those statements.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
No, that's not what I'm saying. What I'm saying is the 6.2L does not come alive until above 3000 rpm. In a 6000 lb SUV, that's a lifetime with a 1600 stall. Once it gets some rpm, the L92 runs like a raped ape. But down low, it's a slug. Since 95% of the time, a truck engine spends its time below 2000rpm, I'd like a little more throttle response and torque off idle and in that 1500-2000 rpm cruise range. Variable valve timing helps. Variable runner length would help. Variable lift would help. Lots of things would help. In the future, all these things will improve with technology. Just expect to see the emphasis on smaller engines making more efficient power than larger displacement engines with bandaids.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
TECH Enthusiast
Joined: Jan 2010
Posts: 578
Likes: 4
From: REALITY
I made a lot of statements in the above post. Are you talking about how slow my 6.2L Denali was until it was tuned?
Or that GM will come out with a scaled down rectangular port head for smaller bore/displacement engines?
Or that the Ford Hurricane 6.2L is a badass engine?
I'd put money on any of those statements.
Or that GM will come out with a scaled down rectangular port head for smaller bore/displacement engines?
Or that the Ford Hurricane 6.2L is a badass engine?
I'd put money on any of those statements.
I am a chevy guy but that new ford is a bad ****.....
Now we are racing SUV's.....lol 5000+ pounds
I can see it now, two Family car SUV's racing down the street....lol like on Meet the Parents.......
On The Tree
Joined: Jun 2010
Posts: 123
Likes: 0
True: LS7 head ........
and the next question would be why would anyone put a L92 head on a 427 when they could use a LS7 head?
But now all 6.0+ trucks have the rec port heads..... The new GM trucks, Silverado,GMC, etc.. now offer a 6.2 L92...... LY6 and L92's .....now if they are so lackluster in torque, I doubt GM would continue to use them especially in heavy duty applications..... Sounds like yall want the ol 8.1 cathedral port headed back....lol
You ve seen the commercials, the truck pulling a ship or airplane, rock, or concrete beams at the construction site......lol and What is this called.....PROPAGANDA AND MARKETING.....
Its coming Pat.....its coming haus..... don't fight the feeling....
jeffreycastgsx: comeback to the discussion bro, I am waiting on the physics.........
and the next question would be why would anyone put a L92 head on a 427 when they could use a LS7 head?
But now all 6.0+ trucks have the rec port heads..... The new GM trucks, Silverado,GMC, etc.. now offer a 6.2 L92...... LY6 and L92's .....now if they are so lackluster in torque, I doubt GM would continue to use them especially in heavy duty applications..... Sounds like yall want the ol 8.1 cathedral port headed back....lol
You ve seen the commercials, the truck pulling a ship or airplane, rock, or concrete beams at the construction site......lol and What is this called.....PROPAGANDA AND MARKETING.....
Its coming Pat.....its coming haus..... don't fight the feeling....
jeffreycastgsx: comeback to the discussion bro, I am waiting on the physics.........
No, that's not what I'm saying. What I'm saying is the 6.2L does not come alive until above 3000 rpm. In a 6000 lb SUV, that's a lifetime with a 1600 stall. Once it gets some rpm, the L92 runs like a raped ape. But down low, it's a slug. Since 95% of the time, a truck engine spends its time below 2000rpm, I'd like a little more throttle response and torque off idle and in that 1500-2000 rpm cruise range. Variable valve timing helps. Variable runner length would help. Variable lift would help. Lots of things would help. In the future, all these things will improve with technology. Just expect to see the emphasis on smaller engines making more efficient power than larger displacement engines with bandaids.
Thats a point im saying, big ports and air flow (or velocity) at low throttle is lost. 260cc are BIG ports, but are pillowed by VVT, and the displacement, but then comes torque management and it makes it worse. Fords are using lots of bandaids and have been doing so for a while, for example there 5.4 3v, makes 290lb-ft torque at 1000rpm, almost as much as a 4.8 makes at peak. But it has VCT, not so big ports, and dual runner intakes, and though it only makes 320hp, it makes more torque (and more peak) across a much wider powerband than a 5.3. That was kinda off-topic but port size has a lot to do with torque.
**** happens... one of my best friends got an 02 burb and we ran twice with my 99 Z-71.. His 16.2xx beat my 16.1xx because I fell asleep at the line and my low 16.xx got his low16.2xx the second race by a fender... My T/A was apart so I wanted to race something damnit!! LOL...