Patron

http://www.yellowbullet.com/forum/sh.../615123?page=1

big hammer

Does a shrouded exhaust valve matter less than a shrouded intake valve?

Patron

Honestly the intake is what makes the hp we can get the exhaust out. Think about what's said about factory Ls3 heads and shrouding of smaller 4.0 bore sizes. I find it funny. Hp is still made compared to better aftermarket casting with better valve location and angles. Cheaper! Not bashing or hating just my OP, from what I've seen. A persons budget is how you Choose heads. And a set of factory Ls3 heads can make 800 so what's the point? A name, casting, budget. Funny! Even with that said they'll all make around the same hp with the same basic engine.

big hammer

Ported stock ls3 castings can flow mega air and make a pile of power. They're just not as nice for a street engine at that point because the ports become huge.

Rise of the Phoenix

iTrader: (27)

The formula for coefficient of discharge is as follows: C/D=airflow/curtain area. Curtain area=valve diameter x Pi x Lift.

Darth_V8r

iTrader: (4)

Don't disagree with you there at all. Even looking at cam events, the first thing you look at is intake valve close. How that intake valve is opening and closing determines most of the way the engine peaks. And you can always just make the exhaust duration longer to compensate for I/E flow ratios.

The trick is for a 4.0 bore and LS3 heads, you make 800 HP with RPM. So for non-drag racing stuff like road course racing, where midrange matters quite alot, these other dynamics do come into play. But, yeah, when you start getting into really high RPM, the larger CSA port will usually rule the day.

Patron

Big Hammer: They as vendor's do offer different programs. So 4 cc's over stock 264 cc's is to large or heck even 7cc. I do get your point, yet if we know camming what then. Your back to what Speed said some time ago. So basically you want a small port head to achieve what? And whether or not to pay for: cat vs rec....again. What intake, well I'll wager that either will be in a ball park/ vicinity with any intake you'd choose.

Rise of the Phoenix : I've read that formula in book about heads once, and I thought to myself that it makes sense to someone who Knows the Dynamics of how a head works(does heads for a living). I generally ask the lets get down from the BS which one would work best. And with these 2 heads what would be the general Difference? Besides 1 being a Cat head made by TFS and a smaller port rec head made by Mast. Again refer back to what Speed said we're just talking about a smaller port. In which we compared TFS 245 to ported factory Ls3 heads. Intake choice and RPM were the main things that affected choice that a person should make. Here's your two head choices and I know darn well you know this thread or page. How much of a difference do you all think the Mast heads being 235 cc vs 257 cc makes on TQ or HP?

http://www.hotrod.com/articles/hrdp-...der-head-test/

Test 5
Mast Black Label LS3 (Small Bore)

Retail price: $2,998
Intake valve size: 2.165
Exhaust valve size: 1.60
Intake port volume: 257 cc
Exhaust port volume: 86 cc
Chamber volume: 64 cc
Peak power: 620.1 hp at 6,600 rpm
Peak torque: 563.3 lb-ft at 5,300 rpm
Average horsepower (3,000-6,500): 477.4 hp
Average torque (3,000-6,500): 523.4 lb-ft
Torque at 4,000 rpm: 514.3 lb-ft

Test 9
Trick Flow 235

Retail price: $2,550
Intake valve size: 2.08
Exhaust valve size: 1.60
Intake port volume: 234 cc
Exhaust port volume: 80 cc
Chamber volume: 64 cc
Peak power: 619.1 hp at 6,400 rpm
Peak torque: 558.2 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 478.4 hp
Average torque (3,000-6,500): 524.6 lb-ft
Torque at 4,000 rpm: 517.7 lb-ft



I figure 1sickengine just maybe the Only Exception in the LSX World as far as Factory Ls3 heads go and talking about CSA and the whole large runner bit with Ls3 heads. Funny! Camming!!!! All the while with a factory stroke & intake. Hilarious!

Big Hammer I do get your point. Your chasing the Wind there is No 1 perfect head just the one meant for you...as any head you choose among whats known will be with in hairs on Hp & TQ with either choice.

pantera_efi

iTrader: (1)

Hi Patron, yes a good report.

I would like to know/add "tech" about the Intake Valve Weight.

My measurement of a 2.165" has been 126-131 gms.
My measurement of a 2.08" has been 96-114 gms.

Lance

Patron

With the test listed anyone who knows anything or can read between the lines knows that if the 235 heads were used Vs 257's(there goes your CSA) TQ would be up slightly and Hp may go *down a bit along with PEAK rpm achieved. It's a wash, that's the simple way of getting the formula of which heads to choose.

Darth_V8r

iTrader: (4)

So, basically, you're saying the shape of the runners don't mean **** as long as it performs the way you want it to, if I read you right...?

In the article you linked below, what if you were building for 6000-8000 RPM vs 3500-6500? Would that not tilt the scales in favor of the larger runner?

JakeFusion

iTrader: (7)

Avg C/D-.200-.600 using posted numbers. LS7 heads are king followed by Cathedral for the most part.

101.48 TEA 255
106.42 TFS 235
106.57 TFS 245
101.48 TEA St2
103.52 MMS 235
104.94 SPS Hay
101.01 MAST 255
102.61 MAST 240
103.18 Ai Dart
107.96 MAST 285
105.56 MAST 305
100.44 Brodix BR7
97.61 Brodix BR3
102.99 MAST 265
107.48 PRC 285

Patron

Yeap on both! (because as most all know the Cat heads make more TQ generally thought due to the Smaller CSA so what happens when you shrink a Rectangular port) Because if were talking the same engine these ain't no C5r heads nor Ls7 heads. So with that said switching from Mast 257's to Mast 235's What, Would be the results if nothing else changes. TQ goes up and Hp may fall a bit if that. I'm Not thinking about a runner, what would be the results in switching to the smaller 235 from a 257. Simple as that, that's reading between the lines and the Writing on the wall if you know heads and were to switch to a smaller head (We KNOW what the 257's did VS TFS 235's).

Yet I know he does Because he's wanting to go to a smaller head in the 1st place. Do the same thinking with going from a 257 to 235. Gonna make around the Same HP as the TFS heads with just as much Tq. Yet it will Peak before the larger 257 heads. Smaller CSA. Oh I Know you know this! So my ? to you is which heads. There gonna make around the Same Hp & TQ. You'd need to consider your intake choice before purchase. Limited models of FAST intakes with differing runners lengths(LS3 only), No high RPM cathedral carb intake. So MSD or Vic Jr / Super for Cat. heads. Your options are open for the Ls3: CID,MSD,MAST,FAST,Vic Jr and Super. The powers still in the same vicinity depending on intake choice. If you switch the intake on the other set of heads (keeping them similar) your back to chasing the wind again. I'll ask with the test listed which heads would you choose (is there really that much of a Diff)? Knowing that a smaller port 235 would increase TQ and bring peak rpm down a hair. My mistake I said it already they'd be neck and neck or a mirror of each other.

Ls3 heads for the win: better intake choices as cathedral port heads Are Not getting anything new. A Future bigger build may require new heads. Port may take to a larger cnc program yet Valve placement may not allow for a larger valve AKA: 3.890+ bore size.

Darth_V8r

iTrader: (4)

So true... Would have loved to try fast102 mid length runners. I'm starting to think that the shape of the port doesn't matter at all. More that the runner size on cathedrals tends to be less than rectangles, so the performance characteristics get grouped together out of convenience.

Honestly, LS3 heads are racecar stuff. they're fantastic heads. I like to get the smallest runner THAT STILL MEETS FLOW REQUIREMENTS. But I build for DD, which means In addition to top end, trying to also preserve a very strong midrange. But there again, that has nothing to do with a rectangle vs a cathedral. Has to do with 235cc vs 265cc runner volume.

What I like about the mast heads is that they allow for converting to rectangles for the better intake options (even the stock LS3 intake is great), but work quite well on a 3.9" bore. IDK if they would be any better than Mamo's stuff on a 3.9, though. But if I was building for 8500 rpm, I would not be using 3.9" bore anyway.

Patron

That's how you should Pick heads and a persons Budget! The fancy talk about discharge coefficient is for the Birds..listen for. Chirping & crickets.. Yet I will say this to you brother because I know your a good guy. With a stock Ls3 or head with a larger runner change the gear or and the stall (if you have the Correct cam). That 30 to 40 ft-lbs of TQ isn't missed. Again* cam the engine for the intended rpm range. What mid range difference would be Noticed then? From knowledge I'll say this Vs a stock Ls3 head the aftermarket Cat's make more TQ in the mid range( CSA and it being factory with 15* degree valve angles ), But a aftermarket set of Ls3 heads what's the Diff? To me really None. Look at any test that had a Cathedral head vs Rectangle head both being Aftermarket. What's the diff? NONE! Look at post #27. It Speaks Volumes. There's also the test in which Mast tested the theory of Cathedrals vs Rectangles. Again it's a wash. Size of the head matched to the bore size not runner styles.

http://www.superchevy.com/how-to/ght...-head-to-head/

It Can't be said enough for most guy's as they try to out think something as Basic as breathing. If you've got the budget cool if not we can make the factory work. Just pick the correct cam and add Fire or * compression* what TQ or HP is Missing when using factory Ls3 heads with a good Cnc. If you got it or if you don't, we all can have or get what we want. The aftermarket starts off at a better place or point but, cost more $$$$ for the initial investment. Simple as that. But! We"re talking about a 3.9 bore and there Is Nothing out there Good From the Factory, Except a aftermarket casting being TFS/AFR/MAST for a smaller bore engine. Do we know of Tony's 383? or the 5.3 with TFS : H/C/I change. It's around 35 cfm Missing with a Factory cathedral head with Cnc. So you really don't have to many being that it's a 3.9 bore.

Another option RHS SMALL BORE LS7 PRO ELITE™ 266CC runner sounds larger yet it's raised so more, so it sounds bigger. I wonder what's the CSA? Better than the heads list as it's based off the Ls7 architecture. Choices! LMAO!

http://www.racingheadservice.com/rhs...266cc-for-ls1-

G Atsma

If a rectangular head could be made with 245cc ports and flow as well as aftermarket 245 cathedrals, the world would beat a path to your door. It might not flow quite as much as a stock LS3 head, but low and mid range would pick up a bunch. The stock LS3 is reputed to actually be a bit too large for the stock LS3 engine anyway.

Patron

If the aftermarket listed the CSA guys could pick heads better. What happens, when a Raised runner head with a smaller CSA has more total CC* than a head with a Larger CSA? You would Not know that by how many CC's.


G Atsma: So true.

big hammer

Your cross sectional area and port velocity required for the purpose of your build are more important than a small difference in flow numbers.

spanks13

iTrader: (5)

https://www.mastmotorsports.com/coll...oducts/ls3-240

Patron

With all this Known I wonder why the same ?'s keep coming up. With a quick google search you have all the Comparisons a person could want and if you don't see it. Read between the lines if you know what I mean.


Mister please stop shooting the horse. It's dead already for goodness sake.

We are only talking about the same companies each time and same ls3,cathedrals and same Ls7 heads. Nothing new under the sun.

big hammer

Those heads are a hot ticket