Exhaust / intake flow ratios on LS heads

[Rick360]

Really good exhaust ports ALWAYS flow good.

Really good flowing exhaust ports AREN'T ALWAYS really good exhaust ports.

Set the AREA of the exhaust throat and port for the engine and try to get the most and smoothest flow for that area.

Rick

[groberts101]

I think a person could get rich doing seminars under the title "How to PROPERLY use a flow bench." The secrets on how to apply what your seeing..

I think is so misunderstood, it's easier to stay away..

my opinion.

Probably make it 2 separate classes or it'll become a 2 year course. Better be committed too.. pretty heavy physics portion in that class curriculum.

I believe the biggest misconception is that a much simpler static flow environment on the flow bench can't possibly mimic the truest physics involved inside an actual running engine. Obviously can't.. why even mention it. Even a wet-flow bench can't possibly show you the true nature of the pulsing air/fuel column but seems to be well established it's at least one step closer than dry flowing the port.

BUT.. what some seemingly ignore is the proven fact that the flow benches data can be correlated and compared with a LONG existing and ever growing data base of known good shapes, flow, size(port speed) as they relate to their supporting combination of parts. Not much doubt in my mind that some of the biggest names.. would not have become the biggest names without use of the flow bench to help reflect what's going on inside a running engine.

Personally, I look at the bench as a seemingly overcomplicated device that's really a very simple gauging tool. Only tells me where I started, what direction I'm heading along the way, and where I finally ended up on the gauge. Then the parts need to go on the engine and get tested, however that may be. And I'm not ashamed to admit to riding coattails like a sum'bitch just to avoid too many back and forth's. I typically mimic other peoples shapes and designs that have similar velocity/flow profile requirement for the various combinations of parts that have been sussed into known good combinations. If the data says that the motor responded to increasing airspeed beyond the point that would typically be accepted?.. that's what I try to mimic.

Feel free to correct me again if I'm wrong here, but it seems the general consensus is that port speeds in relation to any given CSA are generally considered to be a pretty decent reflection of a more optimized SSR shape.. and ultimately the valve curtains overall efficiency. Without the flow-bench.. we were completely blind folded from being able to convert and correlate static flow speeds into torque/power increases on the actual running motor. Flowbench's allow some to do in one lifetime, and actually be able to afford, what would normally take four lifetimes and a truck load more cash to accomplish. So yeah.. despite the physics involved here.. flowbenche's can pretty damned obviously be used to improve a cylinder head design being tested far outside the physical state of the actual running environment. Far from an "intake only" device.

I do agree with the fact that working to increase peak exhaust flow alone is not the best solution on many motors. Not so much because the intake charges mass will never reach that level of flow.. but because it most likely decreased port velocity to reach that now higher and unusable level of flow. It might help reduce pumping losses but softens the port.. reduces its "pulling capabilities". Don't worry so much.. your cam grinder will be able to fix some of it by readjusting the valves flow windows size/timing anyways. Nothing at all wrong with a reverse split design in many applications. Might even be easier on the valvetrain too.

[Stan Weiss]

If exhaust port flow is completely irrelevant, why in the hell the Ford pro stock guys spend so much time/money doing this in the 1970s? Just didn't know any better back then?

cleveland1.jpg

Because the original shape was just ugly. It had a very small radius turn in the port.

Stan

....which made it.....flow poorly?

Yes it flowed poorly.

I do not believe anyone in this thread has every said do not port the exhaust port or not to improve exhaust flow.

My point (I do not want to speak anyone else) is in most cases to use whatever you can on the intake side to get as much mass flow as you can. In almost no case would I remove anything from the intake side to help make the exhaust flow better.

Stan

[groberts101]

I remember a Kasse magazine article from not too long ago where he was asked about flow bias. He said that exhaust flow ends up being whatever it is after he's done modeling it for the purpose. Not at all concerned with some special flow bias # in the least. The numbers were arbitrary.. could be high or low and mattered not one bit so long as the port had been developed well enough for the task at hand.

I'm thinkin' Kasse might know a tad bit more than me.. probably already forgot more than I'll ever learn.. so I'll just go with that.

[Warp Speed]

I remember a Kasse magazine article from not too long ago where he was asked about flow bias. He said that exhaust flow ends up being whatever it is after he's done modeling it for the purpose. Not at all concerned with some special flow bias # in the least. The numbers were arbitrary.. could be high or low and mattered not one bit so long as the port had been developed well enough for the task at hand.

I'm thinkin' Kasse might know a tad bit more than me.. probably already forgot more than I'll ever learn.. so I'll just go with that.

Kinda goes back to post #2 huh?!? Lol

[turdwilly]

cleveland1.jpg

[/quote]

Because the original shape was just ugly. It had a very small radius turn in the port.

Stan[/quote]

....which made it.....flow poorly?[/quote]

Yes it flowed poorly.

I do not believe anyone in this thread has every said do not port the exhaust port or not to improve exhaust flow.

My point (I do not want to speak anyone else) is in most cases to use whatever you can on the intake side to get as much mass flow as you can. In almost no case would I remove anything from the intake side to help make the exhaust flow better.

Stan[/quote]

Agreed Stan, & I wasn't purposely targeting you, I only replied to you because you are the one that replied to my post. I have no knowledge on this stuff - certainly don't have the experience of others posting on this that have had years of dyno, flowbench & track testing. I was just seeing some replies in this thread that seemed to present that the exhaust port flow was completely irrelevant, so I was wondered if that was indeed true, why so much effort was put into the OEM Cleveland heads with their bad exhaust port.

[CGT]

It is what it is, apply lobe area as needed.

As in more area for less "flowz"?

[groberts101]

It is what it is, apply lobe area as needed.

As in more area for less "flowz"?

.. you guys really crack me up sometimes. Oversized kids but the toys just got bigger and the money makes things seem more serious. Thanks Randy.. glad you could inject some Flowz humor into it.

[CGT]

.. you guys really crack me up sometimes

I find you hilarious as well.

[groberts101]

.. you guys really crack me up sometimes

I find you hilarious as well.

Sorry.. don't know you well enough to understand if you're playing nice or not. I might be way out of whack on the whole subject matter?

[CGT]

.. you guys really crack me up sometimes

I find you hilarious as well.

Sorry.. don't know you well enough to understand if you're playing nice or not. I might be way out of whack on the whole subject matter?

Im playing nice...promise.

[Larry Salisbury]

Obviously the exhaust flow is important - no question. But under what conditions??

When the flow is sonic at low lift and high delta P? Or at high lift and low delta P?

The 1400 degree gases at sonic velocity are unrelated to what a flow bench can possibly simulate, and sonic flow has completely different characteristics. Like the velocity increases with increasing area, opposite to sub-sonic. It's a completely alien set of conditions, so is a flow bench the right tool, especially when you consider all the variables? I don't think so, but what do I know. I think the exhaust is way more complicated then a flow bench can begin to simulate. Not saying you can't learn something from a bench though.

Absolutely! Another very important piece of the exhaust tuning puzzle. Flow benches are informational. It''s up to the builder to disseminate that information accordingly. Without flow data E/I ratios could not be calculated.

Larry

[groberts101]

It is what it is, apply lobe area as needed.

As in more area for less "flowz"?

If something has a slow rate then it takes more time. Duration is time.

Hi Chris, from the cam grinders standpoint of designing a lobe from scratch.. what type of flow bias would you prefer to start out with and why?

designing the lobe for a decent flowing head with 320/220?..

or for another with 280/240?

pro's and con's to each cam design?

If you have the time, thanks in advance.

[Leftcoaster]

Hi Chris, from the cam grinders standpoint of designing a lobe from scratch.. what type of flow bias would you prefer to start out with and why?

designing the lobe for a decent flowing head with 320/220?..

or for another with 280/240?

pro's and con's to each cam design?

If you have the time, thanks in advance.

- - and, if an exhaust port achieved "sonic" flow, what changes would you make compared to a non sonic port - -

[groberts101]

Hi Chris, from the cam grinders standpoint of designing a lobe from scratch.. what type of flow bias would you prefer to start out with and why?

designing the lobe for a decent flowing head with 320/220?..

or for another with 280/240?

pro's and con's to each cam design?

If you have the time, thanks in advance.

- - and, if an exhaust port achieved "sonic" flow, what changes would you make compared to a non sonic port - -

dude.. that thought just totally blew my mind.