This thread is comic gold on cylinder heads....

[SStrokerAce]

http://www.ls1tech.com/forums/showthread.php?t=902523

Just awesome, worth the read even when drinking coffee! I actually love the fact that the only people commenting on it are from here and STILL haven't said anything that would give it away!

SupriorAuto why you spillin the beans? Shhhhhh

Bret

[superiorauto]

SupriorAuto why you spillin the beans? Shhhhhh:confused:

[SStrokerAce]

http://www.ls1tech.com/forums/showpost.php?p=9176633&postcount=21

[superiorauto]

Not me, Bret. I do work with Quik, though. I'll tell him. I am sure he does not see the whole picture.

[SStrokerAce]

That would be helpfull, if he still wants to know why E/I% is BS he should ask that over here no reason to stirr up anything because of that thread and a bunch of LSRicers.

http://www.ls1tech.com/forums/showthread.php?p=9162801&highlight=#post9162801

[quik406]

Bret, I hope there is no hard feelings. I am just trying to learn some things about heads. I realize pretty stupid on my part to look on ls1tech:) But I have learned things from fools before.
I enjoy reading your posts. Would you please elaberate on the bs statement. I am confused. I have read

I have NO "NONE" experience with Low RPM pump gas engines with limited compression ratios. I will arrive at the proper intake to Exhaust valve ratio but its going to take some experimentation. The one thing I am NOT going to do is treat the I/E ratio like I would with a Pro Stock engine. I will however call everyone I now who has some good experience with these combinations and ask what they think would be the proper I/E ratio and then give there advice serious consideration.
DARIN MORGAN

I respect Darrins info, I agree crappy formulas are bs, but doesn't there have to be a proper ratio?

So the int to exhaust ratio at 28" of H20 is how the motor runs?

Other than it's me asking this question, we already know the "your a dumb kid response" your going to give here.......

Why does the flow at 28" mean anything in terms of finding the difference between the intake and exhaust duration of the cam?

I would say that how much you put into the cylinder determines how much you need to get out. That requires more than just flow, it needs some idea of pressures that the engine sees. There is no flow without a delta p.

Intake to exhaust flow relationships play ZERO part in telling you what the camshaft wants. That might be a concept that is from the dark side of the moon but it works, particularly when I have seen 70% E/I ratio setups want well more than 12° more exhaust duration to make the most power. If you have formula's or theories on something it has to work in all instances and that is why this intake to exhaust ratio stuff in BS.

Can you elaborate on the Intake to exhaust flow relationships play ZERO part in telling you what the camshaft wants. That might be a concept that is from the dark side of the moon but it works, particularly when I have seen 70% E/I ratio setups want well more than 12° more exhaust duration to make the most power.

Sorry I got pissed I just wanted some more info, and at the time did not know the whole story.

Thanks

[SStrokerAce]

quik,

We have to take a step back into how engines work first to explain that....

The #1 problem of E/I% determining the difference in intake and exhaust duration is that flow is not what makes a engine run. Flow and how it is taught to the average guy, usually from the average guy and is a function of steady state testing which doesn't relate to the dynamic conditions of how motors actually work. Some may argue that is all they have to work with, but that is ignorance to the rest of what is in the physics book. You take out a calculator, snap guages and a measuring tape... maybe add in a computer and now you can guess much more accurately.

Pressure, pressure, pressure is the key. Delta P or the difference in high and low pressure and when it is happening is how you fill a cylinder, how you evacuate a cylinder and how you make or lose HP.

"how much you put into the cylinder determines how much you need to get out."

Cylinder filling or VE% is the first thing you look at, and with some measurements taken to evaluate the harmonic capabilites of the motor you can get pretty dam close to and idea of how much you can put in the motor.

Say two different motors, a LS6 and a LT4. They have the same cubes, the same valve sizes, roughly similar flow numbers in ported and stock forms and very close E/I% ratios around 77% (with a PIPE). What they need for cams in terms of duration on the intake and exhaust, LSA and therfore valve events is grossly different be it a street application or racing application. The big difference is the VE% that they work at and that is mostly due to the intake manifold.

That is just one of MANY reasons why E/I% flow numbers related to intake and exhaust durations is total bullshit.

I COULD elaborate on that some more, but I really don't want to. There are too many half whit's out there doing camshafts that think they know what to do without any rhyme or reason and I really don't like teaching them how the world works.... beyond guys like my father and Joe throwing ideas back and fourth with me I did the diging to figure this out and so should everyone else if they want to know.

Bret

[quik406]

Thanks for the reply Bret. I agree about all the half wits, that is why I want to learn more about airflow, because I know enough to to realize most people are talking out of there ass. Any books you would recommend? I have read quite alot, but always looking for more. Thanks again, I have learned so much from you and your dad!

[OldSStroker]

Thanks for the reply Bret. I agree about all the half wits, that is why I want to learn more about airflow, because I know enough to to realize most people are talking out of there ass. Any books you would recommend? I have read quite alot, but always looking for more. Thanks again, I have learned so much from you and your dad!


Here's my favorite. It's not for the faint of heart..or mind. If you get thru it once, congratulations. You'll probably find yourself going thru parts of it many times. Each time another lightbulb should pop on. At least that's what has happend for me.

http://books.google.com/books?vid=ISBN0768004403&id=rzJMJkdjvGoC&printsec=frontcover&dq=Prof+Gordon+Blair+book


Jon

[SStrokerAce]

Thanks for the reply Bret. I agree about all the half wits, that is why I want to learn more about airflow, because I know enough to to realize most people are talking out of there ass. Any books you would recommend? I have read quite alot, but always looking for more. Thanks again, I have learned so much from you and your dad!

Airflow and how it makes power is not just the cylinder head, that's the hard part. My rule is anyone who just talks flow numbers and port volumes is a "dummy", if they start telling you that velocity is related to port size, they go down a step further on the intelligence ladder. Velocity is one of those bad words in my book, too many guys use it incorrectly and don't understand it at all. Localized velocities are the key not the "port velocity", and you want to control the speed of the local velocities NOT INCREASE IT!

Now when guys talk about discharge coef, port geometry and cross sectional area you are going down the right path. Port geometry and things like "charge motion" are arbitrary phrases that some guys will use and they have no idea what they mean and they use them to blow smoke up your ass. Honestly Mike Chapman is about the only guy I know who can use "charge motion" and acutally not BS you. Port geometry is related to how the tuning pressures work in the head and a better port geometry propigates pressure waves more effectively.

Cylinder head flow IS a valuable evaluation tool, but it's not the only one. I've seen "big name" guys (this was also a big pet peave of Joe's) that will go from one day saying flow numbers mean nothing to that every cfm is worth 2hp.... it's just not the case.

Luckily I got to work with Joe long enough to figure out a lot of the warning signs of cylinder head salesmen and cylinder head porters. You can either listen to them, read what they write OR feel around and look at their ports to see if they know what they are doing. Most times you can figure them out quick!

Bret

[OldSStroker]

Luckily I got to work with Joe long enough to figure out a lot of the warning signs of cylinder head salesmen and cylinder head porters. You can either listen to them, read what they write OR feel around and look at their ports to see if they know what they are doing. Most times you can figure them out quick!

Bret

Joe brought new meaning to "digitizing a port". ;)

Jon

[superiorauto]

Thanks for the reply. Can you elaborate on the localized port velocity. I found out many years back when velocity talk (HV = torque)was all the rage, that it is not always true. I ran a set of 235cc heads(that cc'd 240+) on a 406. Everyone said it would be a turd. To make a long story short, it was far from it. Great throttle response and gobs of torque. Maybe more with smaller heads, but never tried it. It also picked up with a 1050 dominator, that everyone swore would kill it. I am not saying bigger is better, just don't always believe with out my own data.

Why do ls6 motors make more power then LT4 when they are so much alike?
Say two different motors, a LS6 and a LT4. They have the same cubes, the same valve sizes, roughly similar flow numbers in ported and stock forms and very close E/I% ratios around 77% (with a PIPE). What they need for cams in terms of duration on the intake and exhaust, LSA and therfore valve events is grossly different be it a street application or racing application. The big difference is the VE% that they work at and that is mostly due to the intake manifold
What causes the difference in VE%? Do you care to share on the subject of VE%.

[SStrokerAce]

What causes the difference in VE%? Do you care to share on the subject of VE%.

Well, I was going to give you the wikipedia deal on VE% = Volumetric Efficiency but that would be a waste of time after reading it.

What do you want to know about Volumetric Efficiency?


Why do ls6 motors make more power then LT4 when they are so much alike?

Already answered that one.

Say two different motors, a LS6 and a LT4. They have the same cubes, the same valve sizes, roughly similar flow numbers in ported and stock forms and very close E/I% ratios around 77% (with a PIPE). What they need for cams in terms of duration on the intake and exhaust, LSA and therfore valve events is grossly different be it a street application or racing application. The big difference is the VE% that they work at and that is mostly due to the intake manifold.

Bret

[superiorauto]

Bret me and all the guys at my shop have been racing a few years, We try to read and study as much as possible. I have been out of racing for 5-6 years, but the LSX motors have re-kindled my interest. My buddies have great luck with them. The numbers they are running blows me away. We were compairing notes and ideas, and I am really fired up about building HP again. I like building my own stuff and smoking people with big $ sh%t they did't build.

SO..... what should a guy look for in ls heads? Port geometry, How can I learn what is good? Also tuning pressures, and pressure waves ? Is there methods for speculating what VE's might be? Also with what you said about intakes, what do you think about the current carb intake? ls and l92?

Thanks

[SStrokerAce]

I like building my own stuff and smoking people with big $ sh%t they did't build.

You and me both!

SO..... what should a guy look for in ls heads? Port geometry, How can I learn what is good? Also tuning pressures, and pressure waves ? Is there methods for speculating what VE's might be? Also with what you said about intakes, what do you think about the current carb intake? ls and l92?

Only thing I can really tell you is work with the right people who know. A lot of this stuff is not things guys just give away. Some things are things you can learn in the right text books but applying it is the hardest part.

The carb intake is good for a very high stall race motor. If you can leave the line at 4500-5500rpm then that's what you can play with. Even then the thing is not as good as SBC offerings and takes a lot of work to get right.

Bret

[Ed Curtis]

That GM carb intake for the L92 needs some cutting, sectioning and welding. I really don't have a spare to lend out but the POS I was given a long time ago now looks like Frankenstein yet it has a VERY GOOD balance between runners. Ugly as snot dried on a fence post though... Probably just melt it down now since I heard Edelbrock is working on a Super Victor for these heads.

Ed

[SStrokerAce]

I have basically the same thing as a LS7 intake in my shop Ed!

The L92's are screaming for a Super Victor and as long as they leave a little meat in it and not make it have such a low carb flange we might get someplace with it!

Bret

[Ed Curtis]

http://www.edelbrock.com/automotive_new/mc/manifolds/images/2868.jpg

Started looking like this Edelbrock intake... just fuglier....

[SStrokerAce]

That's a Cup or Windsor intake right? That's what we need for the rectangle port LS heads!