Originally Posted by KCS

I think that cam will disappoint you. Way too small for a frickin' 408.

Originally Posted by bortous

......So now I am in the process of building a 408.......I am using a 223/231 111lsa cam utilising Comp lsl lobes.
Any thoughts?

Originally Posted by bozzhawg

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.
Quote:
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 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

Originally Posted by Ryne @ CMS

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

Originally Posted by Launch

Some eye opening poasts

Originally Posted by Darth_V8r

INdeed. MArtin Smallwood said some similar things, too -- said he cringes when people say square ports don't make torque.

Originally Posted by TTur1996

I would like to start by saying that I have Mad Respect for both Tony and Brian. You really can't go wrong with either one. I started out mud bogging and dirt circle track racing. During that time it was plain to see if you didn't have AFR heads you weren't winning. (Real world results). So when we went to build our stroker Ls The 245 AFR's were my first choice. I have seen many guys running Brians Trick Flow cathedral 245's and are fast as **** as well as the AFR's. The real world is majorly different than a Dyno in a building. Hell we had to go up 4 jet sizes at the track from the dyno. From what I have seen at 3 different tracks we go to, none of this Hype about the LS7 and LS3 headed motors applies unless they are over 454ci. Even then they seem to not do well in the first 100ft, regardless of what is posted on the internet. Our car is a fat pig at 3350 race weight and I can tell you one thing for sure. Once we put the Mencer shocks on it. When you let go of that button it launches crazy fast. Our sixty foot is something to be reckoned with. We have raced several LS7 cars with turbos or whatever. 95% of the time we got 2 cars on them by the time they pass the tree, and gets way worse by the time you hit the 330. Then here they come. Problem is they are already smoked. Most of the time they are so embarrassed after running their mouth they leave the track after hearing they got smoked by a Cathedral headed motor. It really is quite comical. The best race we have had was against a 2800 pound fox. We were sleeping at the light and he got a car right off but when we let the button go we jumped immediately past him by 2, and thats how it stayed the whole 1/4 through the traps. Later I talked to that guy and found out he was running a 565 big block ford on alcohol. Spraying 300 with alcohol too. We were only spraying 200 and we are all race gas. He was pretty pissed when he found out our weight and the fact it was a cathedral head LS. So everyone can believe what you want. I'm not a numbers guy on parts. Real world results is what I see and all I care about. I wouldn't trade these cathedral AFR heads for the world, and all the guys I know with the cathedral Trick Flows will tell you the same thing. They are both fast as ****. From what I see is the guys that are using power adders are going back to the cathedrals because they just don't see the results the internet says on the rectangles. Its the guys that are N/A and need every last tenth that are doing good with the Rectangles. I've said it many times. Go in the drag racing tech section and see what Kenny has done with a 245 cathedral Trick Flow headed motor with one 83mm turbo on his 98 camaro. His 60ft is crazy too. It really is quite impressive to say the least. That thread alone should wake everyone up in this argument.

Originally Posted by spanks13

The cathedral/square port discussion recently is almost more exhausting than back 10+ years ago lol. Y'all are cherry picking literally one of the largest and best aftermarket castings to trash on all ls3 port heads and even saying LS7 heads don't make good torque.

Originally Posted by G Atsma

People are missing on one detail of rectangular port heads.
They do just as well or better than cathedrals at full throttle. BUT at off idle and low throttle settings, not so much. That is where the higher flow velocity of the cathedrals comes in.
That is why rectangulars were never adapted to the 4.8/5.3 bore size. The bottom end response would have gotten pretty soggy.

Originally Posted by G Atsma

People are missing on one detail of rectangular port heads.
They do just as well or better than cathedrals at full throttle. BUT at off idle and low throttle settings, not so much. That is where the higher flow velocity of the cathedrals comes in.
That is why rectangulars were never adapted to the 4.8/5.3 bore size. The bottom end response would have gotten pretty soggy.

Originally Posted by bortous

Also G, the ls3 head needs at least a 4 inch bore to clear the valve so no chance of that head fitting on a 4.8 or 5.3.
You are right, it would be soggy as hell.

Originally Posted by 64post

The thread that wouldn’t die.

Originally Posted by bortous

Yeah.
They do make torque but they feel lazier and not as crisp in the low and mid range rpm.
Most likely with anything less than an ls3 bore size would you say?
Also up top they felt lazy too on my old engine.
If these were originally designed for a 4.125 bore size I would say they require that size bore to work their best.
Wasn't the LS3 head meant to have gone on the z06 but gm scrapped it in favour of the ls7 style head?

Originally Posted by Darth_V8r

Generalities always break down at some point. Saying "Cathedrals are apples, and Square ports are snowcones" is no different than arguing what LSA does what in a car. Looking at variables in a vacuum is what's going on in all of these discussions.

The LS7 style head was developed before the LS3 style head. how do we know? C5R. And, because the LS7 debuted in 2006, and the LS3 debuted in 2008. LS3 heads were designed to move air for a 4.065" bore without needing much cam to do it. One of the biggest problems is people cam ls3 heads like they're cathedrals, and they respond differently.

BTW - how many people actually think the cathedral head was designed the way it was to make a certain flow pattern? They made the port taller, because there was an intake valve in the way of making it wider. The cathedral shape was a compromise. Enter offset rockers, and the ports can be wider now, so yay team.

Take a cathedral headed 416 and swap to a set of LS3 heads. Let's say it was cammed at 240/248. You'd want to drop the intake duration some. So you end up at 236/248. that's where the wider splits end up coming from. not the soggy exhaust side -- the insanely good intake side requires less duration to move air. Then an internet expert chimes in and says, no you should cam it at 240/252, because 416 likes massive cams (another generality). Now we've added duration to the exhaust instead of cutting from the intake. Then the story becomes, "I swapped to ls3 heads and lost torque", when the storyline might actually be "I overcammed my engine and lost torque"

ANY engine overcammed loses torque. So, overcam a LS3 head, then claim they make no torque. Cathedral heads tolerate being overcammed better than ls3 heads, so in the big cam tests, they tend to look better. Too bad GM wasn't as smart as the aftermarket, or they'd have put 243 heads on all their 6.2L trucks...

OK /rant

before I get in trouble...