School us on engines...

billfisher said:

how far ahead of it's time was the BOSS 351 head?

260cfm froom a heads designed in the 60's. too large of an exhaust port, but tongued headers fixed that.

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Well I remember them needing to epoxy the floor of the intake port to make the CSA smaller to get the velocity up. Also remember them cutting over the top 1/2 of the exhaust port and adding an aluminum plate so they could raise and straighten the exhaust port.

billfisher said:

i read some engine experts articles on the new hemi and it's high tech high velocity ports. they compared them to F1 in terms of velocity and efficiency. add cnated valves, and wellah. 6.1L 425hp. kinda smokes the other brands.

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You keep talking about high velocity ports. At what average FPS does the flow of an intake port become high velocity?

rpm______2k___2.5k__3k__3.5k____4k____4.5k__5k___5.5k___6k___6.5k

Avg_In_Vel 94__ 117__ 141__ 164__ 188__ 211__ 235__ 258__ 282__ 305
Avg_Ex_Vel 141_ 176 __211 __247 __282 __317__ 352 __388 __423 __458



those are average velocities for unported 5.4 3v.

the writer didn't get specific on the port velocities for the hemi, but when it says near F1,you tell us. i cannot help that, but i assume from his explaination that they are higher than ? hell i don't know. i consider these stock smallish ports on a 5.4 to be high velocity.

as for the 351C and all that work you are talking about.... so what. they performed fine on the street stock with the exhaust ports reduced. why would you guys do all of that work instead of purchasing some yates heads?

what type of racing were those totally changed heads used for.

you have totally misunderstood my intentions. i am not trying to be some kind of expert. i have enough knowledge to do my own work and certainly improve the heads i use without going overboard and ruining them. do i have velocity probe and a flow bench? of course not, but that doesn;t mean i cannot pick the brains of those that do and watch them so i can do my own.

i have posted plenty of time Al papito will do my heads if i choose to go beyond what i know to do. but that's a big IF. i have studied this stuff for 22 years, and i've picked up enough reading and in fluid dynamics class in college to do a good job. that's all. just don't try to shove bull crap up my ass and call it flowers.

this is a cut and paste from the article.

http://www.popularhotrodding.com/tech/0403phr_chrysler_hemi_57_liter_345ci_engine_review/



note the low lift required for max flow.


Flow Capability
We can see that Chrysler's engineers were targeting the best two-valve head possible. There are two important questions that need to be asked here: How well did they succeed for the head in stock form and, since no aftermarket heads are available, what is its porting potential? The graph, Fig 3, gives the answers here and you are going to like them. First, the intake port. The stock port with its 2-inch valve flowed a whopping 270 cfm at only .600-inch lift. It hit the peak flow figures, which are produced at .700-inch lift on a stock LS6, at only about 375 thousandths lift. This is good news but there is a lot more. Peak figures are not the whole story. Good mid-range figures are also important. The new Hemi did extremely well here. At 250 thousandths lift, the stock head was nearer a $10,000 Winston (Nextel) Cup head than it was to even a good modified parallel-valve head.



A check on the intake port velocity (Fig 4) showed the intake to be a super high-speed port with valve-to-port areas very similar to what is seen in Formula One. Velocity probing showed 90 percent of the port flows at a velocity greater than 90 percent of maximum. This is far better than a typical 23-degree performance head for a small-block Chevy or, for that matter, the LS6.

i must mention that the srt-8 heads is even better.

so those velocity charts define for me, a high velocity port.

why did you ask that question? are you trying to be like the other guy and "call me out" what does that do for you? who cares.

those are the only thing i do to a port. if it needs more, an expert does it.

a little work on the bowl, reshaping the guide bosses, removing the swirl brows, 3 angle, etc.

billfisher said:

rpm______2k___2.5k__3k__3.5k____4k____4.5k__5k___5.5k___6k___6.5k

Avg_In_Vel 94__ 117__ 141__ 164__ 188__ 211__ 235__ 258__ 282__ 305
Avg_Ex_Vel 141_ 176 __211 __247 __282 __317__ 352 __388 __423 __458



those are average velocities for unported 5.4 3v.

the writer didn't get specific on the port velocities for the hemi, but when it says near F1,you tell us. i cannot help that, but i assume from his explaination that they are higher than ? hell i don't know. i consider these stock smallish ports on a 5.4 to be high velocity.

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The 305 looks OK. Could be a higher and still OK. The 458 looks a little high to me. I do not know what he means but F1. He could mean F1 racing motors, which I have no idea about.

billfisher said:

as for the 351C and all that work you are talking about.... so what. they performed fine on the street stock with the exhaust ports reduced. why would you guys do all of that work instead of purchasing some yates heads?

what type of racing were those totally changed heads used for.

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This was 30 + years ago in NHRA PRO Stock racing. Bob Glidden, Gapp and Rouse did this.

Today CHI heads look like the hot setup.

billfisher said:

you have totally misunderstood my intentions. i am not trying to be some kind of expert. i have enough knowledge to do my own work and certainly improve the heads i use without going overboard and ruining them. do i have velocity probe and a flow bench? of course not, but that doesn;t mean i cannot pick the brains of those that do and watch them so i can do my own.

i have posted plenty of time Al papito will do my heads if i choose to go beyond what i know to do. but that's a big IF. i have studied this stuff for 22 years, and i've picked up enough reading and in fluid dynamics class in college to do a good job. that's all. just don't try to shove bull crap up my ass and call it flowers.

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Since want want to make this personal, I am done.

sorry dude. i didn't want to make it personal.

i wasn't referring to you shoving but the other guy.


they didn't have an option back then. again sorry.

billfisher said:

this is a cut and paste from the article.

http://www.popularhotrodding.com/tech/0403phr_chrysler_hemi_57_liter_345ci_engine_review/



note the low lift required for max flow.


Flow Capability
We can see that Chrysler's engineers were targeting the best two-valve head possible. There are two important questions that need to be asked here: How well did they succeed for the head in stock form and, since no aftermarket heads are available, what is its porting potential? The graph, Fig 3, gives the answers here and you are going to like them. First, the intake port. The stock port with its 2-inch valve flowed a whopping 270 cfm at only .600-inch lift. It hit the peak flow figures, which are produced at .700-inch lift on a stock LS6, at only about 375 thousandths lift. This is good news but there is a lot more. Peak figures are not the whole story. Good mid-range figures are also important. The new Hemi did extremely well here. At 250 thousandths lift, the stock head was nearer a $10,000 Winston (Nextel) Cup head than it was to even a good modified parallel-valve head.



A check on the intake port velocity (Fig 4) showed the intake to be a super high-speed port with valve-to-port areas very similar to what is seen in Formula One. Velocity probing showed 90 percent of the port flows at a velocity greater than 90 percent of maximum. This is far better than a typical 23-degree performance head for a small-block Chevy or, for that matter, the LS6.

i must mention that the srt-8 heads is even better.

so those velocity charts define for me, a high velocity port.

why did you ask that question? are you trying to be like the other guy and "call me out" what does that do for you? who cares.

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I ask that question because there is no set numbers that I know of for high velocity port. It varies with the source. It is like what is a long rod motor? Drag racing was around 1.9 R/S, NASCAR 2.0 R/S, and some 12-13k RPM motorcyles 2.1 R/S.

From you link:
This computer-generated velocity map shows that about 90 percent of the port flows at 90 percent or more of peak velocity. This is a high-efficiency port from race engine territory, not typical production-line stuff!

You will notice David calls it a "high-efficiency port" with number and terminology varying I just wanted to be able to talk apple and apple not oranges.

I am not sure where Bill got those velocity numbers from for the 5.4 head, but they are not just high, they are off the charts high. I doubt those are even real as if they were, that head would have so much local airspeed induced sonic choke they would be absolutely junk heads. On a small block head, even with 3 valves, anything over 340-350 FPS will start to show a power loss. I’ll explain why below.

Some people will make their own pitot tube. Usually a 180° bend in the end of the sampling tube works best to get it down inside the port to measure the velocity pressure at different points. If the pitot probe velocity pressure readings are the same or higher than your flow bench test Pressure, then there's a real good chance your Engine's TQ/HP will not correlate to what you expect from your flow bench numbers. You can look at the velocity pressure or you can convert the velocity pressure into FPS.

FPS(feet per second) = ( Pitot Velocity Pressure ^ .5 ) * 66.2

On certain low valve angle racing heads (less than 12°) you could run 350+ FPS @ 28.0" H20 and not see TQ/HP losses, but the overall port geometry would have to be just about perfect to keep the a/f mixture in suspension and attached to that specific shape throughout the port. On a street/strip small block head like ours, when you start to go over 300 FPS (20.5" pitot pressure at 28.0" flow bench testing depression) you can watch as it will start to induce a premature sonic choke condition on the flow bench with the pitot tube right around the area of the SSR apex. The curtain area should be the choke point, or in other words the curtain area should be where you observe peak local airspeed. If you observe a peak local airspeed anywhere other than the curtain area, you will likely have a problematic cylinder head. When you are flow testing at 28.0" H20, the higher the pitot velocity pressure is above 28" (350 FPS at the pitot tube) and the greater that distance is away from the curtain area, the more power you will lose. Something else that will hinder power is to have a specific area of very high velocity near the SSR apex, or a side of the of the port wall that is in excess of 350 FPS coupled with a significantly slower downstream velocity, that velocity differential will cause fuel separation and will significantly increase your odds of having a sonic choke condition.

There is also a low limit local airspeed that is commonly accepted to be true. This is 240 FPS or 13.14" pitot velocity press when flow testing at 28.0" H20. When you start to go below 240 FPS, you will lose power on any head, especially in the lower RPM range at increased throttle angle. Piston speed and rod/stroke ratio also have an effect on the way a port responds at low RPM increasing throttle angle. On a small stroke motor like ours with a relatively large rod/stroke ratio, that 240 FPS will be way too slow and that motor will lose torque. Torque is obviously important at low RPM part throttle situations.

Also when comparing valve lift to port velocity, low lift flow (meaning anything below 1/2 of the total lift) is relatively unimportant. Think about the valve events in a motor for a moment. From the point when the valve first lifts off its seat until it reaches mid lift, the piston is either going the wrong way (rising towards the top of the cylinder) or it is experiencing dwell near TDC. The piston doesn't begin to move away from the combustion chamber with enough speed to substantially lower the pressure in the cylinder until the valve is nearly halfway open. High lift flow and a relatively low velocity port will make the most power and perform the best on the street or drag strip.

you are right concerning those numbers. they estimates made by a sim that takes the ports dimensions, the motor's dimensions, the port length, the intake manifold flow coeficient , flow bench numbers of the port, etc and cycles them to produce an estimated velocity at various RPM's using cam dimensions.


the exhaust port on a 3v is real bad. those numbers are the basis for power estimates.

they are not flow bench FPS. i don't have 3v velocity charts on the flow bench.

i retract those staements. i can be a bar of lead sometimes.

my writing style is what it is. i fragment a lot, so i apologize for it. these guys are used to it. you are not.

OK I will start by saying I do not own a flow bench. I have a great number of heads for which I have calculated a number of different numbers on. I use FPS = ( CFM / CSA ) * 2.4. The bowl (CSA) cross-sectional area is calculated using 90% of the valve diameter with nothing removed for valve stem area. NOTE removing valve stem area would reduce CSA and increase FPS. dc = Discharge Coefficient of the exhaust. I use an SAE formula for Discharge Coefficient.

I calculated these number for '96-'98 Non P.I. 4.6L Ported BHPerformance 34mm exhaust valve

cfm 186 191
lift .500 .600
fps 392 402
dc .606 .518

There are other above 400 FPS on the exhaust.

again my apologies for the unremarkable things i say sometimes.


certainly sonic "choke" is the end of an intake port. 260 FPS is a good torque peak velocity for exhaust gasses in a header tube.

i guess it can be summed up with....

don't be too enamored with huge ports with massive numbers. IMO which i am allowed.

Stan Weiss said:

OK I will start by saying I do not own a flow bench. I have a great number of heads for which I have calculated a number of different numbers on. I use FPS = ( CFM / CSA ) * 2.4. The bowl (CSA) cross-sectional area is calculated using 90% of the valve diameter with nothing removed for valve stem area. NOTE removing valve stem area would reduce CSA and increase FPS. dc = Discharge Coefficient of the exhaust. I use an SAE formula for Discharge Coefficient.

I calculated these number for '96-'98 Non P.I. 4.6L Ported BHPerformance 34mm exhaust valve

cfm 186 191
lift .500 .600
fps 392 402
dc .606 .518

There are other above 400 FPS on the exhaust.

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Often velocity mapping is misuderstood (not saying you)....especially exhaust velocity. Most magazines and engine builders fail to incorporate the calculations of thermal expansion and contraction from heating and cooling that occurs during blowdown and pumping losses. Blowdown is the window of time within a 4 stroke motor just after the exhaust valve begins to open. Right as the exhaust valve comes off the seat, the cylinder pressure is higher than the exhaust pressure. Under ideal conditions...blowdown will occur while the piston is still experiencing dwell at BDC. During blowdown, the exhaust gas expands isentropically.

When the rag mags and buiders fail to incorporate these respective calculations to factor out the effects of blowdown and insentropic exhaust gas expansion...the resulting numbers they come up with will always be much higher than they actually are in a dynamic live engine.

The best thing to do...that we have found...is to compare the intake and exhaust velocities and make a model showing them as a ratio.

mogs01gt said:

LOL I think you missed the point Bill was making. I always thought the term "elephant" derived from the late 50s and early 60s "Hemi" engines but was directly slapped on the 426 "Hemi's".

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One more time to clear up this confusion and we will let this Elephant thing rest.

The 426ci Hemi motor made from 1964-71 (not the wedge headed motor) was the ONE..AND..ONLY motor called the Elephant. The 426ci Hemi motor had exceptionally large dimensions unique to itself such as cylinder bore center to center spacing, deck height, block web thickness, bore pitch, camshaft height, etc..... This is why it was given the name the Elephant.

Fast Eddie said:

The best thing to do...that we have found...is to compare the intake and exhaust velocities and make a model showing them as a ratio.

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who is 'we'?


the velocity map i posted was given from software the Ed Olin recommended.

not that he is god, but he is somebody.

why should anyone use methods other than a powertrain engineer chief at SVT recommends?

not confronting, but why?

Fast Eddie 41 said:

One more time to clear up this confusion and we will let this Elephant thing rest.

The 426ci Hemi motor made from 1964-71 (not the wedge headed motor) was the ONE..AND..ONLY motor called the Elephant. The 426ci Hemi motor had exceptionally large dimensions unique to itself such as cylinder bore center to center spacing, deck height, block web thickness, bore pitch, camshaft height, etc..... This is why it was given the name the Elephant.

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Im not confused. I never said it wasnt.. I said the term derivied from the earlier engines or R&D and then was tagged onto the 60's Hemi's..

Engines just don't get labelled the day they come out. Look at the ls1, its called the millennium engine and it was called that even before it was released.

billfisher said:

who is 'we'?


the velocity map i posted was given from software the Ed Olin recommended.

not that he is god, but he is somebody.

why should anyone use methods other than a powertrain engineer chief at SVT recommends?

not confronting, but why?

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The "we" he was referring to is he and I (Kevin). Like Matt said, it's an excepted rule of thumb to compare intake and exhaust flow/velocity as a ratio. Depending on the type of head and the application, you will get the intake where you want it, and then dial in the exhaust flow/velocity as a derived percentage of the intake.

I have no idea what you are rambling about speaking of a SVT engineer??

mogs01gt said:

Im not confused. I never said it wasnt.. I said the term derivied from the earlier engines or R&D and then was tagged onto the 60's Hemi's..

Engines just don't get labelled the day they come out. Look at the ls1, its called the millennium engine and it was called that even before it was released.

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The Elephant term did not come out a single day before the first 426ci Hemi was put together....how could it have nobody except for the design team had even seen or heard of the motor yet. LOL When that first 426ci Hemi rolled out into a car in 1964...shops sarted getting their hands on it and realized the abnormally big dimensions. The name "elephant" started being thrown around and it just sorta stuck. Who calls the LS1 the millenium motor?? Kevin (laserred01GT) and I have been in this business as partners for a while now. Over the years the majority of the cars we have worked with were GM....and hence the Gen III LSx motors. The first Gen III was the LS1 and it was built in 1996 only to be put into the first C5 Corvette in 1997 and then the F-Body in 1998. We talk to a good portion of some of most well know LSx builders in the country and we have never heard anyone in the business EVER call the LS1 the millenium motor...LOL

Hey Stan you seem to have a pretty good understanding of motors...ask Kevin(laserred01GT) about flourescent wet flow testing.

Fast Eddie 41 said:

The Elephant term did not come out a single day before the first 426ci Hemi was put together....how could it have nobody except for the design team had even seen or heard of the motor yet. LOL When that first 426ci Hemi rolled out into a car in 1964...shops sarted getting their hands on it and realized the abnormally big dimensions. The name "elephant" started being thrown around and it just sorta stuck. Who calls the LS1 the millenium motor?? Kevin (laserred01GT) and I have been in this business as partners for a while now. Over the years the majority of the cars we have worked with were GM....and hence the Gen III LSx motors. The first Gen III was the LS1 and it was built in 1996 only to be put into the first C5 Corvette in 1997 and then the F-Body in 1998. We talk to a good portion of some of most well know LSx builders in the country and we have never heard anyone in the business EVER call the LS1 the millenium motor...LOL

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Hey Matt, let's call our 4.6 2V motors, the Modular Madhouse Monster's of Mayhem!

Fast Eddie 41 said:

Hey Stan you seem to have a pretty good understanding of motors...ask Kevin(laserred01GT) about flourescent wet flow testing.

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Thanks for the very kind words.

I have seen some pictures from Darin Morgan / Reher-Morrison Racing Engines of wet flow. Interesting but very strange looking.

LaserRed01GT said:

The "we" he was referring to is he and I (Kevin). Like Matt said, it's an excepted rule of thumb to compare intake and exhaust flow/velocity as a ratio. Depending on the type of head and the application, you will get the intake where you want it, and then dial in the exhaust flow/velocity as a derived percentage of the intake.

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Which is more important the flow or velocity ratio. I have seen heads done by pros where the exhaust to intake is less than 80%. When I calculate the velocity of both at the bowl area it is over 100%. A good example would be the windsor heads Ported HRD. I use FPS = ( CFM / CSA ) * 2.4. The bowl (CSA) cross-sectional area is calculated using 90% of the valve diameter with nothing removed for valve stem area.