JakeFusion

iTrader: (7)

Maybe not if you swap the plastic intake. But with a plastic intake, it's true more times than it's not.

Once you swap to a big single plane and put a cam with higher lift in there, I think a lot of the "down on power" scenarios we see go away.

There's no way I'd run a TFS LS3 head without at least .700 lift. So Solid Roller time.

NAVYBLUE210

.650"-.700" is the sweet spot for TFS LS3 Heads, without considerable
Work they stall ~.700"+
.680" worked pretty well for me.

Patron

Navyblue, you don't necessarily have to stop lift because of the airflow stalling in a worked over head and even some aftermarket heads that stall. Know of 3 guy's that used some older ET heads Now Mast* that stalled at .700 and .800+ lift cams were recommended and used. Each did some nice things on the dyno.

Martin Smallwood

iTrader: (2)

Right, for example if a certain cylinder head is more efficient from .300-.500 vs. another cylinder head that is more efficient from .600-.800+ you wouldn't run a .600" lift cam with the head that is more efficient from .600-.800+. You'd run a .800+ lift cam to take advantage of that. For a hydraulic roller application with an OEM style intake I'd choose the head that is more efficient from .300-.500 all day long. For a solid roller race application with a good aftermarket intake I'd take the head that is more efficient from .600-.800+.

It's all about application and again, cross sectional area, throat diameter (this is where the MCSA in the head should be), and curtain area. When you have the proper area at the plenum, at the MCSA in the head and you have the needed curtain area to meet the demand of a given combination is when things start to really happen.

It all comes down to area.

Tuskyz28

NAVYBLUE210

Patron,
Understood, good point. I just wanted to point out over .700"
lift wasn't necessary in my application to get the results I was
targeting, thereby hoping to have the valve springs last little
longer by staying under .700" lift vs over.

Patron

I'm with you Navy.


What Mr. Smallwood has stated is Correct. Again So Correct yet no one will put the truth out there about heads. It's all advertisement to make the sale with a flow number . Certain RPM ranges Require a certain amount of CSA for a given engine size so as to still have TQ relatively low and make peak Hp. A professional head porter and cam guru know this and will Always ask what's the size of the engine and intended use to port the heads for a perfect CSA. I personally know of heads that have a larger CC runner but smaller CSA Ls7 vs a Smaller CC runner and Larger CSA Ls3. Both Custom ported.

KCS

iTrader: (20)

Out of curiosity, how does one determine if a head is more efficient at .600-.800" or .300-.500"?

NAVYBLUE210

Coefficient of discharge perhaps, E/I Relationship, combination?

Tuskyz28

Airflow at each lift point/Valve diameter x Pi x lift = Coefficient of discharge

Thanks to Brian Tooley for the formula that he gave me years ago.

Patron

Navy once Again your on to something, yet I never personally got the formula(Don't need it or want it). I've just dealt or deal with the *Best* in cylinder heads and each has there own formula and Honestly it has always worked out(G.Good*has always helped me with heads non done by Him/D Morgan/C Frank/ C. Boggs is next). My thing is the flow numbers and guy's who say name X ported them and it did this. And the car runs like Crap or can't make a ET with $ spent. I've done it pretty much all on Heads and the game Speaks for it self. And some disagree with how another one does heads but in the end I've always done right and good by each porter and any set of heads done. Here's a kicker bought a 2k 2500 6.0 and 4l80e for 300 bucks , another 4l80e for 300 hundred bucks at the job(wrecked work truck). Looking for the min on cylinder wall thickness on all sides Major thing is Thrust side. If over .230 = 427 with a lq9/4 simple and then say Hello people I'm now in the ball game Cheap. 900+ just because of the bore. They say I suffer from A.D.D. as I never focus. I think I'm just always a *Head and never get stuck. LOL.

Patron

For the basic guy's who don't Know how heads work.

Someone posted a good post with D. Morgan and Engine builders here's one even older with 2 of the best. And flow numbers are last on the list.

http://www.enginebuildermag.com/2007...ead-selection/

KCS

iTrader: (20)

I know CoD, but at first glance I thought Martin was saying that a head can be more efficient at .600-.800" than at .300-.500". Using Discharge Coefficients to determine efficiency wouldn't make sense because it's almost physically impossible to have a head with better CoD numbers that high in the lift range, which is why I asked how one would determine efficiency.

But after rereading what Martin said, I think I understand now that he was actually saying that you want to pay attention to the efficiency of a head in different lift ranges depending on the application. For example, in a big lift solid roller combo, the CoD numbers in the .300-.500" range wouldn't be as important as the numbers in the .600-.800" range and vise versa. Using CoD to determine efficiency then makes more sense.

big hammer

good thread OP

KCS

iTrader: (20)

It's not the thrust side you should worry about, it's the wall thickness between the cylinders. That's where they usually crack. Most 6.0L blocks have enough space between the cylinders to fit a 1/8" diameter rod through pretty loosely. That means they're about .140" thick at just a 4" bore.

Tuskyz28

I was also told by Brian Tooley to focus on the .300 to .500 lift numbers for a engine that's go spend most of its life on the street.
I think that's a great tip for anyone when choosing a head for a street/strip car.

big hammer

For your average cookie cutter street build I can see that being right.

Tuskyz28

Well I guess you don't care for power under the curve no how... Remember the highest cfm head ALWAYS wins at the track. Otherwise I know better....

Patron

Both of you guy's are right the thing is having a CSA designed for the engine size which in general will be small Enough to have faster air speeds which will give you decent flow numbers in the mid range while still flowing into the upper range. The faster air speeds with mid lift are what give you the off the line quick responsiveness and as you go the down the track the upper cfm of the heads are now what we are looking at yet with the Correct CSA the Airspeed will still be fast as the port was designed and meant for your engine size. Win Win situation. As I said before, I've seen Ls7 heads that you can Physically look at and can see that the CSA is Smaller vs Ls3 heads with a more open CSA. But most would think that the Smaller CSA Ls7 heads has less CC's for the runner size. Wrong! The Ls7 heads measured in at 275 cc with the smaller CSA and the Ls3's came in at 268 cc's with a bigger CSA. Again done by two great guy's who I know have done 9 second heads with engines less than 420 cubic inches.



KCS the space between the cylinders or water passages on the block. Couldn't I 1/2 fill it with hard block to help. I haven't gotten the chance to break the engine down yet to sonic test it but hoping there's enough meat to try it. Heck I'll take .090 to.100 over if I can. Anything other than the normal .030 & .060 over blocks that are typically talked about.

KCS

iTrader: (20)

The top half would still be thin. I think Blown06 had some photos of his 6.0L block on YB and it cracked it the upper portion of the cylinders.