Cylinder head porting claims...
Originally Posted by Studytime
On race motors you'll be very hard pressed to find a CNC ported head that's not hand finished. What does that tell you? Also, there is no reason for there to be ridges in the runners. Actually a smooth intake runner wall provides the best power. Makes sense? No. I've taken fluid dynamics and this should not be the case, ...
I don't doubt that a CNC'd runner could be improved upon by someone hand porting it. I know, I did it with my 243's
I believe this is because of the clearances that a CNC machine is confined by. I've never seen a CNC port that shows that the CNC tool was able to go from end to end. Because they can't reach all the way through there's a point they have to stop and then start back up from the opposite side creating a small ridge. Just by taking out this ridge, I'm sure there is flow to be had. 
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I'm not going to argue anything posted because I don't own a dyno, or a flow
bench.
Reading a couple of sources states otherwise however. I found an article on
Wikipedia which was also backed up by an R-M reference that stated:
Smooth surfaces impede air flow due to a thin boundary layer. This slow moving, or static air promotes fuel separation from the air stream.
Rough lines, or small grooves that run perpendicular to the air stream reduce
fuel separation and improve air flow within the intake port.
Quoted from Wikipedia:
"within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished port and a rough textured port is typically less than 1%"
I would imagine track testing would show a larger margin once fuel has been
introduce along with dynamic pressure changes in the runner during a 1/4 mile pass.
bench.
Reading a couple of sources states otherwise however. I found an article on
Wikipedia which was also backed up by an R-M reference that stated:
Smooth surfaces impede air flow due to a thin boundary layer. This slow moving, or static air promotes fuel separation from the air stream.
Rough lines, or small grooves that run perpendicular to the air stream reduce
fuel separation and improve air flow within the intake port.
Quoted from Wikipedia:
"within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished port and a rough textured port is typically less than 1%"
I would imagine track testing would show a larger margin once fuel has been
introduce along with dynamic pressure changes in the runner during a 1/4 mile pass.
I'm beginning to put less faith in head work. Just Friday I saw a motor go from the mid 280s to 320 cfm head flow on a 23* head. It was a 355 ci SBC that picked up zero on a DTS engine dyno at 7400 RPM with an additional 30 cfm at peak and with improvements all across be board from valve job technology and back cutting the valves. Flow quality went from good to beyond great (for a 23* head) and power didn't change. These were pontiac SBC heads fwiw.
I've also seen atleast two other 355 chevy motors in the last two weeks not pick up anything from an additional 20 cfm. Really baffles me. With all this said, the difference in gains from a slightly low relative surface roughness to a higher one (such as a CNC) would be even less.
This data is coming from a DTS dyno and a SF600. With all this said, if you want more power increase your camshaft size and spin your motor higher. I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
I've also seen atleast two other 355 chevy motors in the last two weeks not pick up anything from an additional 20 cfm. Really baffles me. With all this said, the difference in gains from a slightly low relative surface roughness to a higher one (such as a CNC) would be even less.
This data is coming from a DTS dyno and a SF600. With all this said, if you want more power increase your camshaft size and spin your motor higher. I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
Oh, and I just wanted to say that my posts are written taking fluid dynamics into consideration. I studied fluids at Louisiana State University in my four and a half years in the Mechanical Engineering program there. 
Ben T.
Ben T.
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I'm sure there are a few head porters on this site that will jump all over your post (to support your data).
Flow numbers aren't always the tell tale sign of a strong engine. After reading
your post and your findings, it certainly backs up what they are preaching.
Flow numbers aren't always the tell tale sign of a strong engine. After reading
your post and your findings, it certainly backs up what they are preaching.
Originally Posted by Studytime
I'm beginning to put less faith in head work. Just Friday I saw a motor go from the mid 280s to 320 cfm head flow on a 23* head. It was a 355 ci SBC that picked up zero on a DTS engine dyno at 7400 RPM with an additional 30 cfm at peak and with improvements all across be board from valve job technology and back cutting the valves. Flow quality went from good to beyond great (for a 23* head) and power didn't change. These were pontiac SBC heads fwiw.
I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
#1: Port Velocity.
#2: Check out some 3400 lbs stock eliminator cars running stock 23* heads and huge cams in the 10s all day long.
It's about the entire setup, not about each individual part.
I wish I could get some more input on this from other head porters. How can an engine go from 280 to 320 cfm and not pick up more power with the same everything else? The port shape on those Pontiac heads is about the best you'll get for a 23* head too. Everything was done right on all three of these engines I'm describing. I could understand that ideal valve events would change as head flow increases, but not showing any gain makes me wonder what's going on. Each case was extensively tested at varying EGTs and timing and on different fuels. The intake and cam weren't changed and the big tube dyno headers were of course not changed.
Ben T.
Ben T.
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Originally Posted by Kraest
#1: Port Velocity.
...
...
What was your point with the LT1 cars?
Ben T.
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Originally Posted by Studytime
How can an engine go from 280 to 320 cfm and not pick up more power with the same everything else?
other depression? How does the flow react when fuel is added? What did
the low and mid lift numbers look like?
Originally Posted by Studytime
I could understand that ideal valve events would change as head flow increases
The valve events are timed for the pressure pulses and RPM, not necessarily
flow of the runner.
Obviously you don't understand about the laws of diminishing returns when it comes to head porting.
To put it simply:
Too much head porting = loss of air speed and the ability to fill = loss of power.
Have you checked out what Advanced Induction has done with their LT1 stuff? Amazing. If you haven't, you need to.
Mike
To put it simply:
Too much head porting = loss of air speed and the ability to fill = loss of power.
Have you checked out what Advanced Induction has done with their LT1 stuff? Amazing. If you haven't, you need to.
Mike
Originally Posted by Kraest
Obviously you don't understand about the laws of diminishing returns when it comes to head porting.
To put it simply:
Too much head porting = loss of air speed and the ability to fill = loss of power.
Have you checked out what Advanced Induction has done with their LT1 stuff? Amazing. If you haven't, you need to.
Mike
To put it simply:
Too much head porting = loss of air speed and the ability to fill = loss of power.
Have you checked out what Advanced Induction has done with their LT1 stuff? Amazing. If you haven't, you need to.
Mike
"The laws of diminishing returns when it comes to head porting"? Please... I'm not even going to point out the ignorance in your naive posts or humor you with a response.Ben T.
Last edited by Studytime; Jan 14, 2007 at 01:14 AM.
Originally Posted by Adrenaline_Z
What depression did the improvement occur? Was the head tested at any
other depression? How does the flow react when fuel is added? What did
the low and mid lift numbers look like?
I wouldn't be so sure that valve events would change as flow increases.
The valve events are timed for the pressure pulses and RPM, not necessarily
flow of the runner.
other depression? How does the flow react when fuel is added? What did
the low and mid lift numbers look like?
I wouldn't be so sure that valve events would change as flow increases.
The valve events are timed for the pressure pulses and RPM, not necessarily
flow of the runner.
Did I read you have been investigating head flow data at higher DPs?
Ben T.
Last edited by Studytime; Jan 14, 2007 at 01:16 AM.
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Did I read you have been investigating head flow data at higher DPs?
head porters, as well as texts from reliable sources.
I've been a little intimidated to port heads to date because of the complexity.
The more I read the more I think I know what I would do starting out...on the
other hand, it seems like a slight error could seriously ruin a port design.
I'd say the biggest tip I've picked up is to start with a relatively small volume
port and concentrate on the valve/valve seat area. Keep the air speed as
high as possible to allow for cylinder filling. Probe around with a pitot to find
the weak spots of the port.
Originally Posted by Adrenaline_Z
No, not at all. The extent of my investigating stops at reading posts from credible
head porters, as well as texts from reliable sources.
I've been a little intimidated to port heads to date because of the complexity.
The more I read the more I think I know what I would do starting out...on the
other hand, it seems like a slight error could seriously ruin a port design.
I'd say the biggest tip I've picked up is to start with a relatively small volume
port and concentrate on the valve/valve seat area. Keep the air speed as
high as possible to allow for cylinder filling. Probe around with a pitot to find
the weak spots of the port.
head porters, as well as texts from reliable sources.
I've been a little intimidated to port heads to date because of the complexity.
The more I read the more I think I know what I would do starting out...on the
other hand, it seems like a slight error could seriously ruin a port design.
I'd say the biggest tip I've picked up is to start with a relatively small volume
port and concentrate on the valve/valve seat area. Keep the air speed as
high as possible to allow for cylinder filling. Probe around with a pitot to find
the weak spots of the port.
Port the straight side until you break through the head bolt hole and sleeve it and then port the curved wall until you break through the pushrod area slightly and just epoxy it. Shape the short turns on a bench slowly taking away material at a minimal rate. I'm sort of kidding around, but without trying you'll never know what you're missing out on or how much fun/entertaining it could be. Ben T.
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Joined: Sep 2004
Posts: 188
Likes: 1
From: Houston, TX
Originally Posted by Studytime
I'm beginning to put less faith in head work. Just Friday I saw a motor go from the mid 280s to 320 cfm head flow on a 23* head. It was a 355 ci SBC that picked up zero on a DTS engine dyno at 7400 RPM with an additional 30 cfm at peak and with improvements all across be board from valve job technology and back cutting the valves. Flow quality went from good to beyond great (for a 23* head) and power didn't change. These were pontiac SBC heads fwiw.
I've also seen atleast two other 355 chevy motors in the last two weeks not pick up anything from an additional 20 cfm. Really baffles me. With all this said, the difference in gains from a slightly low relative surface roughness to a higher one (such as a CNC) would be even less.
This data is coming from a DTS dyno and a SF600. With all this said, if you want more power increase your camshaft size and spin your motor higher. I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
I've also seen atleast two other 355 chevy motors in the last two weeks not pick up anything from an additional 20 cfm. Really baffles me. With all this said, the difference in gains from a slightly low relative surface roughness to a higher one (such as a CNC) would be even less.
This data is coming from a DTS dyno and a SF600. With all this said, if you want more power increase your camshaft size and spin your motor higher. I'm beginning to put less faith in what I thought was the most critical aspect of a performance motor- the cylinder heads.
Ben T.
On The Tree
Joined: Sep 2004
Posts: 188
Likes: 1
From: Houston, TX
Originally Posted by Adrenaline_Z
No, not at all. The extent of my investigating stops at reading posts from credible
head porters, as well as texts from reliable sources.
I've been a little intimidated to port heads to date because of the complexity.
The more I read the more I think I know what I would do starting out...on the
other hand, it seems like a slight error could seriously ruin a port design.
I'd say the biggest tip I've picked up is to start with a relatively small volume
port and concentrate on the valve/valve seat area. Keep the air speed as
high as possible to allow for cylinder filling. Probe around with a pitot to find
the weak spots of the port.
head porters, as well as texts from reliable sources.
I've been a little intimidated to port heads to date because of the complexity.
The more I read the more I think I know what I would do starting out...on the
other hand, it seems like a slight error could seriously ruin a port design.
I'd say the biggest tip I've picked up is to start with a relatively small volume
port and concentrate on the valve/valve seat area. Keep the air speed as
high as possible to allow for cylinder filling. Probe around with a pitot to find
the weak spots of the port.
Find someone with a flow bench that will let you use it and just jump in with both feet. That's the only way you'll learn. Forget about surface finish for now because you're hunting elephant. Debating surface finish is akin to the "What's the best wax" debate. If you get up to the Pro Stock level then it'll be a concern. Go to speedtalk andread all of Larry Meaux's posts. While I don't agree with everything he says, he does has a good handle on port sizing.
Last edited by Greg Good; Jan 14, 2007 at 01:03 PM.
On The Tree
Joined: Sep 2004
Posts: 188
Likes: 1
From: Houston, TX
Originally Posted by Brian Tooley
Take the TFS 215 head for example, if you sand the intake port surface smooth....it will flow less air, if you sand the seat area....it will flow less air. Pretty much anything you do to it, will make it flow less air.
well their claim is no cnc ported head will *match the performance* .... that`s hard to do anyway the exact hp or flowor dyno number or what ever .... they didn`t say they are better! just not cpparison .... mayby their the worst and that`s why the other cnc perted heads will not MATCH.. -Joking- and maybe they meant what it`s suppose to mean that they`ll outperform ALL the GM castings CNC ported heads .... well why don`t TEA or PRC take that challenge or an vendor that do cnc porting! but please before they say stage 2 R was the a better choice for that test or our 2e heads or 33ZFGJYTF head talk with them first .... hehehehehe