ct06gto

Thats a really bad test. The afr setup was chocked by a 78mm intake and 78mm tb. While the l92 was using a 90 mm tb.

Wnts2Go10O

iTrader: (12)

l92 heads also hve 230cc runners, not 260

jeffreycastgsx

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.

airflowdevelop

Smaller runners create more bottom end? "Simple Fixes"?

Tell me more!

jeffreycastgsx

Whats to tell? The physics was exaggeration.

melsie68

iTrader: (8)

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.

bozzhawg

Yes explain more...... on the physics... so the smaller port, faster velocity, and continue with the rest..........

And also explain why more torque is built....

thx

71 chevy

iTrader: (18)

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.

Patrick G

iTrader: (14)

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.

98Aggie

iTrader: (19)

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.

bozzhawg

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.........

Patrick G

iTrader: (14)

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.

anthony soprano

iTrader: (1)

The L92 makes ~10% more torque than the cathedral head LQ9. The L92 also has the benefit of more cam (both lift & duration), more compression, variable valve timing, and a host of other variables that aren't being accounted for; improvements in exhaust, intake, tune, etc. Has anyone determined how much of that 10% torque bump was a result of the square ports vs. the other variables?

airflowdevelop

are you confident enough in your statement to put a friendly bet behind it?

Patrick G

iTrader: (14)

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.

airflowdevelop

If I understand what you are trying to say...

you like L92 heads...but you believe on a 6.2L engine the cathedral port head makes more tq?

Patrick G

iTrader: (14)

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.

bozzhawg

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.......

jeffreycastgsx

I can't exactly say that more torque will be built with a smaller port, but i can say that a head with a smaller port, that flows just as much as a bigger port head, will have a much meatier powerband. Down low wont be as sluggish as the bigger as well. I'll get into detail tomorrow as its past my bedtime.

Still here.

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.

SOMbitch

iTrader: (8)

**** 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...