Eric: Paraphrase: "A larger valve, makes the cam lobe seem more aggressive than it is; it makes it behave like a lobe with more acceleration." -This is such an important concept and I've never heard it put quite this way before. This is one of the reasons that LS and LT engines always seem to have less cam duration vs. an SBC, isn't it? -If the intake port flow is keeping up with the piston demand closely at each degree of rotation, then you don't need more airflow / curtain area. -I remember seeing a chart from Stan Weiss showing an engine's intake flow curve over it's piston demand for each degree of rotation, and the intake was playing catchup even as the piston was traveling back up the bore. Seems like an engine with a better valve angle, which supports a larger valve and therefore more curtain area and FLOWZ, would have the intake "keeping up" with the piston demand better, and it could therefore close sooner -hence less duration required/ ideal. Wait.. This is why when you look at increasing stroke with the same bore size people start to say that the longer stroke engines end up "valve limited", isn't it? -The longer stroke / faster piston speed just increases the piston CFM demand at each degree and you just end up with a larger CFM "Deficit" between what the piston is asking for and what the intake system is providing, isn't it. *Brain Explosion*!
The thing you should think about with stroke is how the piston speed changes through the stroke. That’s what rod stroke ratio AND stroke together determine. The bigger stroke say a 4” vs 3.625” will have a faster speed right after it stops. It will develop piston speed quicker, than the shorter stroke. This means that if the port and valve can flow for the volume desired (think volumetric efficiency at that rpm and load), it will flow more. This is why you need a more aggressive cam for a bigger stroke; the lobes ramp up and down more quickly so that the valve spends less time at barely open. The bigger valve helps this. A good head like Eric shows, has flow at mid and low lift as well as peak. Same thing with duration… it all comes together. These are all reasons why you can have a milder softer cam in a smaller displacement.
@@th600mike3 its also why tighter and tighter LSA are required for a stroker . The strokers piston decelloration and going away from tdc acceloration is much faster compared to bdc where it sits there for a long time in comparison to tdc . Thats a small rod ratio for ya and its not all bad !!! To me a long rod engine with say 1.9 rod ratio is far easier to over cam or over valve in comparison getting aggressive .
Bischoff's pretty smart guy,... (small block's, even big one's),... Jon Kaase,... (big,.. short rod motor's,.. a ford thing)..... these guy's are both very smart and have mega-hours of research,... and dyno time,....... KEEP UP THOSE NOTEBOOK'S,....... all the best builder's and designer's have them,.... think I got that issue,... it 's all about that air,... hydrogen and oxygen,... I enjoy the video's,.. thank's Eric,...... take care.......
My favorite head ever on a 340 Mopar was a set of ported 273 heads. They were 1.92” intake and flowed only 235 cfm @28” at 0.600” lift. However, they flowed 205 cfm @0.300” lift @28” of water. They were killer on the track.
Darin is the best teacher I've ever had. The patience he had with me while teaching me to grind and diagnose was instrumental in my growth as an induction specialist.
Good things to think about, Eric! It points out that it's not good to get fixated on one number when there a dozen of them that govern how much power an engine can make. And it's difficult to even have a discussion between different head porters working on different heads on different flow benches. There are many ways to calculate coefficient of discharge. Some people calculate it based on valve head OD, some calculate it based on valve throat ID, and some calculate it based on the min flow areas at each stage of valve lift. Comparing numbers that are based on different physical quantities is a waste of time. Coefficient of discharge is a constant of proportionality between how much flow there could be, and how much there actually is. It can be used as a barometer to show where more work could be done to improve things.
A guy did my heads like that, just cut seats to fit a larger valve, my 350, went to running like a 305! I took them off, to change springs, and a rebuild. No wonder , the valves were in it's own way! And shrouded! I didn't think the shrouding would hurt too much, but where the valves were sunk in it shrouded that much more, killed low lift flow, I almost threw the heads in the river! But then I thought that's money, if I was going to do anything, I was going to throw one through his shop window, the other through his car window! But I'm not like that, it was a good feeling thinking about it! I ended up fixing them myself!
Awesome vid Eric. I remember reading the actual "Engine Masters" magazines back in the day. I loved them, because they were so informative for me ,as I was just getting into the "Hot Rod" hobby at that point. It's cool to learn new ways to apply the math and be able to compare in further detail the theroy behind these impressive builds. Thank you.
One last question to put a pin in this subject: With an engine where the intake CFM flow is considerably behind the piston's "demanded" CFM, the only way you're making up the deficit is to continue to try to fill the engine as the piston is traveling back up from BDC -and this is how you end up with >100% VE, right? --When the engine is trying to cram more air into the cylinder on the way up -isn't this when the coefficient of discharge is the most important? Wouldn't a faster air/fuel mixture bring with it more pressure to keep filling the cylinder those last few degrees? Or is this all about PRESSURE differentials and the speed / coefficient of discharge through the valve curtain area not actually matter for cylinder filling when the piston is moving up the bore? (Hmm... An engine's VE is greatest at the TORQUE peak RPM when just happens to be where all these filling variables work the best together in your engine.??..) Does a larger valve size change the engine's torque peak? If so, up or down in RPM?
Coefficient of Discharge by itself is a worthless # until you tie in Cylinder Displacement and RPM into the equation. Coefficient of Discharge only addresses Potential of a Cylinder Head; it doesnt address how a Cylinder Head will behave on different displacements.. Until you qualify how the Cylinder Head sees the Cylinder within RPM, Coefficient of Discharge means nothing. In other words, how does your 220cc Port respond sitting on a 302 V8 vs sitting on top of a 427 V8? What you (we, or all of us) are attempting, is to qualify small, medium, maximum sizing relative to expected mild, medium, maximum output within the category intent of pump gas or race gas in which the engine is suppose to operate in. You are dealing with airflow velocity degrees of efficiencies relative to mild, medium, maximum output at a specific RPM. Edit: BTW, good video with real numbers, and proper approach to identifying Cylinder Head parameters
You're misunderstanding what discharge coefficient is. It's a simple ratio between two different mass flow rates via the same method of discharge. For example, your stock intake valve flows 262 cfm, your ported intake valve flows 350 cfm, the discharge coefficient is .75:1. What you're referring to is "mass flow rate". That's the rate in which the air enters the combustion chamber by way of the valves cross sectional area. What Tooley was saying is true, if when you are finished with your cylinder heads and the discharge coefficient has increased, they will make more power. Plain and simple.
I wish I could post a picture of the porting book I have from Darin Morgans porting class it has part of what you are saying but it based on max flow at curtain area vs what is possible. In your example just making the port larger making flow more it would make more power. It is more complex than that. Hence using an area formula with it.
@@WeingartnerRacing I never said if you make a port larger it will make more power. What if that giant port has a tiny 1.25" ID valve seat? Now what if you install a 2.5" ID valve seat? You will of course have a discharge coefficient between the two and one will have a higher mass flow rate. The one with the higher mass flow rate has the higher power potential.
Abseloutly spot on. I have several times experienced the same. Like an engine where the piston wanted 250cfm and i could only flow 195 but by fitting a Big valve killing the dc but adding like 15 cfm it made more power all over the curve If your engine wanted like 190 cfm and you Can flow that with a smaller valve and your dc increase it Will make a lot of more power. But again there is a lot going into it, sec choke , avg airspeed , peak airspeed , airspeed change over time, CSA , engine aplication and so on.
On a stock sbc vortec head with minor blue printing and a fresh 3 angle cut.. I'm considering throwing the intake valves into the lathe and turning the circumference down.. I know it sounds backwards but the seat and where the valve rides is more than 1, 5mm from the edge on stock valves.. I know the optimum solution would be to port the head to suite the valves and then cut a new 3 angle seat.. But this is for a boat and I'm not going to do that.. I was considering the lathe because it would unshrowd the valve a bit.. But would it improve the airflow? (I'm considering cutting 0.6 - 0.7mm on the radius)
I am curious about on a 13 degree head, the SSR is tight. What throat percentage do you recommend for a 2.19 / 1.66 valves in a 4.16 Ford FE 428 CJ head? It came with a 2.09/166, but the Medium and High Riser Tunnel Port had up to 2.25 valves in 4.23 bores. If I can find some aluminum heads I’d like to find three so that you can experiment like you did with the LS head, and I wish I had an intake slab cut at the valve cover rail so it would compare with other heads. Jay Brown is developing a 2 piece intake like the old PSE that had a valley to head casting that allowed Cleveland intakes to bolt on. One of those center pieces would be great when doing FE stuff.
What was the interruption at 11.47 that was weird great explanation this shows how an engine with bigger valves big camshaft can valve float and make less power
The low lift flows are controlled more by the valve job and valve shape. From off the seat to under .400 lift. I can have a small or a big valve in the same head and the flow will be very simular with the same valvejob. Also I dont go by curtain area as defined. I use gauge pins and lift the valve to a given lift and measure the distance between the valve and the seat. This become important when changing the valve angles. Things like different seat angles and back cuts on the valve can change this area dramatically. Example no back cuts on the valve and a 30 degree seat angle will have far more area between the seat and the valve than a 60 degree with a back angle. Try it and you will see that the steeper the seat for example you will need to lift the valve farther in order to equal the same area as let's say a 45 degree seat angle.
Eric curtain area can be deceiving as it describes the area from valve od on the valve head straight down to the valve seat. However if you take a head , lift the valve let's say .600 lift with a 45 degree valve and measure between the seats, then grind the valve to 60 degree and re-measure you will see what I mean. When you grind the valve to test keep the seat width the same to keep it relevant in comparison
Vortecs aren't a very good head for high lift flow so they wouldn't be the best ported. They are strictly designed for swirl. They make great torque and flow up to about .500 lift and 400hp. But I don't think you'll ever see a ported vortec head that makes 600+hp N/A.
if i have a 2.02 on vn aussie v8 heads and i want the 91 percent throat you say flows the best what size am i looking for please and how do you measure it
hi good afternoon mr Eric I need to know if you can recommend AFR head for 454 Ls for approx 1000 HP. for the sake of the streets and the heads to octimize them "I mean to work the head for you Mr. Eric
What are your thoughts of mirror polishing the exhaust port? Or the chamber for that matter? Just crossing over thoughta from porting 2 stroke cylinders to keep the carbon from building up and changing how the engine runs over time.
Hi, I really think BT Is one of the smartest guys!!!! ( I saw him talk about this on the tuner school video) I completely see your point a bigger valve even if not as great is still bigger and could flow more... I have a zl1 1le (lt4) would you just port the stock heads or get something else? BTR cam lifters, push rods trunnion upgrade (rocker arms??) cai, headers, magnuson 2.6 for road racing could not get a stick...so it has a 10 speed thanks
This may be off point but I want to ask about cutting into the head bolt holes, I`ve flowed them before and it doesn`t seem to hurt flow at all but what im concerned about is the integrity of the head. With the use of studs with the fine threads and increased torque the clamping pressure has to be much more than a bolt. A customer had a set of heads done and I`m concerned about crushing the head............ its a BBC aluminum and there`s 2 holes in each head, can I have youre thoughts on this?
Cool vid.hi isn't vavle curtain 25% of valve diameter?been porting for a little while everyone does there own things which is cool.when you say a sluggish isn't piston drawing or pulling more air then before which lower mean port velocity or ramming effect compared to standard valve just needs more rpm to create more velocity to get port efficiency.or cam change.ring seal is so important to port co efficiency from overlap to ramming effect hopefully equilibrium between intake charge and cylinder pressure.just that piston doesn't get mentioned much when it comes to porting Imagine doing all that head work and piston ring have to much blow by loss hp.peace
If you look at the shape of the chamber that the valves are in and you have the minimum amount of restriction to the intake valve seat the more power your going to make and the exhaust side of the head even with a smaller valve size as long as it to has minimum restriction to flow it's really about chamber size and shape of the chamber to unshroud the valves and port size that makes the most power. 🤔
Not exactly. You still need restrictions in a port to manage air speed. Otherwise you would have a sewer pipe size hole that flows a metric fuck ton of air, but doesn't make ANY power. More to it than that.
Im kinda new to all of this so it was good to get a good explanation of the fundamentals. How does exhaust flow come into play in all this? Is it important to power production?
A engine is a very complex system, very dynamic, we may never completely understand what is going on, ya can't always quantify the complex system we call a engine, it's a very complex air pump, it's a pulsing system it's difficult to test that on a flow bench, pulse flow acts different than steady state,,,
Does this apply to generally all BBC heads as well? My brother keeps saying the exhaust is the problem on BBC. I see a lot of big intake valves in BBC makes me think your theory applies to them as well.
Good info. I'm glad I didn't find this when I was doing my research before porting my heads as it would have only confused the situation. Ray Mondello claims that 90-91% is way too large for a street head but okay for an all out race head. I put larger valves in my heads because I got up into the 90% range in order to blend sharp edge on the bottom of the seat into the bowls. The +1mm valves brought me back down to about 86% since this is going to be a mostly street driven car. I haven't run the engine yet so we'll see. This was my first port job. I actually just uploaded a video on it if you want to check it out over on my channel. Thanks for the information!!
The throat size knows nothing about street and race. Have tons of customers who drive race cars on the street, should we have two separate heads with small and big throats? It's about air speed and power. 90% is NOT too big for a street engine. Where your minimum cross section is in the port also matters. It is also different for every engine. 86% is too small for an exhaust valve, let alone an intake. And becomes a choke regardless of valve size. Nothing wrong with following one person who you think is right, but don't feel like you will be confused when someone else does something different. Either way you will learn something, good or bad.
@@jrdmotorsports9718 Thanks for the reply. I'm all ears and all for learning! I get what you're saying. What came up a lot in my reading was that for low-mid rpm the larger throat sacrifices velocity, and therefore is not the ideal choice for a street driven car. Obviously nobody is gonna swap back and forth between multiple sets of heads depending on how they're driving the car that day. My question was more to say that if a car is predominately street driven is a 90-91% throat too large. I guess what I really was asking is- is it ideal for a street driven vehicle? I ended up cutting my valves down to +.5mm which brought my throats up to around 88%. I am concerned I didn't open the exhaust ports up enough for the tulip valves I installed, but we'll see. The motor is in the car, just have some wiring stuff to sort out. I'm going to share more on my heads, the ratios I ended up with and the power it made once I get it on the dyno if you care to subscribe and have a look. I'd be happy to hear your thoughts and opinions once we can look at the dyno graph along with the head numbers. Anyway, I do appreciate the reply. Take care.
@@BradfordsGarage Throat size is relevant to where the MCSA is in the port. The mcsa SHOULD be at the throat, but it isn't in all heads. Most street engines have the mcsa upstream, away from throat, and by making the throat too small doesn't help, regardless of the rpm. With the mcsa at the throat, it is critical to size it correctly to the valve size, which should be sized correctly to the bore size. Then comes curtain area. It's ALL relative. Too small of a throat, becomes a choke and does not aid in velocity at higher rpm, especially when the mcsa is upstream of the port. When mcsa is upstream, and the throat is small, once the venturi convergence are is bigger, air speed starts moving up the throat and causes chaos....
@@jrdmotorsports9718 I see. Well, the dyno will give the final say. I just got the engine fired up yesterday, so will be getting it on the dyno in the next couple of weeks. Thanks again for the reply.
@@BradfordsGarage Actually, the TRACK would give the final say. A dyno, like a flow bench, is just a tool. Tools that CAN and DO lie to you. The car has the final say. Good luck!
Well to jump in on the conversation that I just got about the larger intake valve someone put a 202 in it well I started doing heads around 1980 for about 20 years of it and no flow bench or anything but everybody wanted to get 202 heads and get more power and all that stuff kind of like going from a 650 Holly to a 750 and then going up to an 800 double pump it ruins everything I built a set of small block heads for myself and it since the valves were free! I put it in a set of 39 heads the problem with it is I didn't have any money to buy what I wanted but the LeMans cam I had didn't wake up until four grand with the 194th if I would have put 190 160s in it it would have changed it and the velocity would have changed but again I didn't have a lot of money so I did what I could do but not necessarily bigger is better at least in the mechanical world
I think it was David Vizard who found that using a 1.9 intake with a 1.7 exhaust (a Ford windsor valve I believe) actually flowed better on a forced induction SBC than the commonly held 2.02 / 1.6 . People think its all about intake and getting it out of the engine doesnt matter in the scheme of things, but the dyno proves differently. Its not a 2 stroke people, and thats another totally different can of worms that I wont get into here lol
Probably because he never changed the throat size. It’s only without any other work done besides cutting to larger valve have I seen a larger valve make less power.
One person promoting 50 year old technology or one point of view is not something that is the end all be all... either there is a reason or they may just show you what can happen if you follow their narrative. Certainly not the best way to make power.
Another, rarely scene possibility is the valves is the perfect size for the cam and the cam is the perfect size for compression and cylinder etc etc and now a bigger valve doesn't match the rest of the criteria. Now it's the weakest link of the system because the rest of the system
I think u hit the nail on the head! Something can be important and still not be everything. Kind of like boost, everyone trying to make more boost. Need more boost. Cooler air is many times better than more boost!
Your comments at 6:50 are somewhat misleading. You say that the throat of the 2.08 valve is 1.8928 and the throat of the 2.10 valve is smaller at 1.89. This is physically impossible. Putting a larger valve in doesn't magically reduce the actual physical size of the throat. It only reduces its relative size, as a proportion of the new valve diameter compared to the old valve. Therefore the assertion that the throat diameter becomes smaller is flawed. It must be 1.8928 in both cases so the calculated CSA must remain the same too.
Thanks your the video. Just here to learn a good example of engines is the 302 chev and the 302 ford Cleveland . The ford in my option had a better heads and could get by with less camshaft
This also explains why "on paper" 4 valve engines often seem to have milder cams then a comparable 2 valve engines. Because 4 smaller valves have more area then 2 large valves inside the same cylinder 4 valve engines act like 2 valve engines that have had huge valves installed so any lift, duration, and overlap "acts" bigger. 4 valve engines, I've figured out with messing with cam timing, are much more sensitive to overlap (they don't need as much).
All highly rod ratio , displacement , cam duration , and camshaft LSA SENSITIVE !!!! Easy to get in trouble with shorter strokes , long rod and tthir longer rod ratios , smaller displacements and lower rpm , too much duration and Wide LSAs and not nearly enough cam advancement !!!!
At 13:35 you hit the key point. CD is dimensionless and relative. thus a lower CD on a bigger port can still move more air than a best in class CD on a more modest port. Where CD is really good, is comparing a/b on the same port or bellmouth. And in real terms anything over 90% is excellent. Though higher CD's are possible on larger ports ;)
[2min] Brian Tooley Racing goes over why bigger isn't always better when it comes to the size of your cylinder heads or valves: th-cam.com/video/Qqg3z60ISQo/w-d-xo.html
I get what he is trying to say but when you put a larger valve in most times the low lift flow is better. This keeps coefficient of discharge virtually the same. If it only flows what the smaller valve did then you need to modify things. You also have more area available than the smaller lift. You need more area for higher rpm.
I have never cared about Cd. It seems like a stupid measure. You will almost never see someone using a smaller valve to increase the coefficient of discharge. It is never successful. Richard holdener harps on about Cd and often fails to realize that its airflow that makes horses. He has said a bunch of questionable things about gen3 sbc 706/862 heads and how they make power because of the high Cd. When you point out that every single aggressive aftermarket porting package adds larger valves its usually crickets.
Legendary engine builder Darin Morgan and Preston Mosher, BES Racing Engines’ cylinder head department manager, dedicated over 90 minutes at the 2021 PRI Trade Show to providing an overview of various combinations built by BES Racing Engines based on 50- to 60-year-old engine architecture utilizing modern cylinder head, induction system, and valvetrain technology to produce ever-higher power levels.
![รวมเพลงลูกทุ่ง 6 หนุ่มไทบ้าน ฮิตติดกระแส ชุดที่ 1 l มนต์แคน ไมค์ ไผ่ เสถียร ไหมไทย พี [Longplay]](http://i.ytimg.com/vi/GD2v1OjMw5I/mqdefault.jpg)
Eric: Paraphrase: "A larger valve, makes the cam lobe seem more aggressive than it is; it makes it behave like a lobe with more acceleration." -This is such an important concept and I've never heard it put quite this way before.
This is one of the reasons that LS and LT engines always seem to have less cam duration vs. an SBC, isn't it? -If the intake port flow is keeping up with the piston demand closely at each degree of rotation, then you don't need more airflow / curtain area. -I remember seeing a chart from Stan Weiss showing an engine's intake flow curve over it's piston demand for each degree of rotation, and the intake was playing catchup even as the piston was traveling back up the bore. Seems like an engine with a better valve angle, which supports a larger valve and therefore more curtain area and FLOWZ, would have the intake "keeping up" with the piston demand better, and it could therefore close sooner -hence less duration required/ ideal.
Wait.. This is why when you look at increasing stroke with the same bore size people start to say that the longer stroke engines end up "valve limited", isn't it? -The longer stroke / faster piston speed just increases the piston CFM demand at each degree and you just end up with a larger CFM "Deficit" between what the piston is asking for and what the intake system is providing, isn't it.
*Brain Explosion*!
By George, I think he's got it!
The thing you should think about with stroke is how the piston speed changes through the stroke. That’s what rod stroke ratio AND stroke together determine. The bigger stroke say a 4” vs 3.625” will have a faster speed right after it stops. It will develop piston speed quicker, than the shorter stroke. This means that if the port and valve can flow for the volume desired (think volumetric efficiency at that rpm and load), it will flow more.
This is why you need a more aggressive cam for a bigger stroke; the lobes ramp up and down more quickly so that the valve spends less time at barely open. The bigger valve helps this. A good head like Eric shows, has flow at mid and low lift as well as peak.
Same thing with duration… it all comes together. These are all reasons why you can have a milder softer cam in a smaller displacement.
@@th600mike3 its also why tighter and tighter LSA are required for a stroker . The strokers piston decelloration and going away from tdc acceloration is much faster compared to bdc where it sits there for a long time in comparison to tdc . Thats a small rod ratio for ya and its not all bad !!! To me a long rod engine with say 1.9 rod ratio is far easier to over cam or over valve in comparison getting aggressive .
Bischoff's pretty smart guy,... (small block's, even big one's),... Jon Kaase,... (big,.. short rod motor's,.. a ford thing)..... these guy's are both very smart and have mega-hours of research,... and dyno time,....... KEEP UP THOSE NOTEBOOK'S,....... all the best builder's and designer's have them,.... think I got that issue,... it 's all about that air,... hydrogen and oxygen,... I enjoy the video's,.. thank's Eric,...... take care.......
Air is 79% NITROGEN (not hydrogen) and 21% Oxygen. Just clarifying that.
My favorite head ever on a 340 Mopar was a set of ported 273 heads. They were 1.92” intake and flowed only 235 cfm @28” at 0.600” lift. However, they flowed 205 cfm @0.300” lift @28” of water. They were killer on the track.
Darin is the best teacher I've ever had. The patience he had with me while teaching me to grind and diagnose was instrumental in my growth as an induction specialist.
Thank you. Great explanation. This has just opened up a whole new world of information.
I miss the magazine days couldn't keep me out of them
Eric, you're killing it with these videos, I've studied this stuff for years and this information is great.....thanks and keep'em coming
Good things to think about, Eric! It points out that it's not good to get fixated on one number when there a dozen of them that govern how much power an engine can make. And it's difficult to even have a discussion between different head porters working on different heads on different flow benches. There are many ways to calculate coefficient of discharge. Some people calculate it based on valve head OD, some calculate it based on valve throat ID, and some calculate it based on the min flow areas at each stage of valve lift. Comparing numbers that are based on different physical quantities is a waste of time.
Coefficient of discharge is a constant of proportionality between how much flow there could be, and how much there actually is. It can be used as a barometer to show where more work could be done to improve things.
Love the hot rod magazines!
Thank you for the time to teach the lesson!
Thanks for watching maybe someday I will get rich from this.
I cant get enough of this stuff !! Thanks for sharing your knowledge much appreciated !!!!!
One of your best videos ever, thanks for sharing. There is so much in here I'll have to watch it a couple of times. j
I remember reading in Carcraft in the 80s where they would cut the valve down in circumference hang it on the edge of the seat.
A guy did my heads like that, just cut seats to fit a larger valve, my 350, went to running like a 305! I took them off, to change springs, and a rebuild. No wonder , the valves were in it's own way! And shrouded! I didn't think the shrouding would hurt too much, but where the valves were sunk in it shrouded that much more, killed low lift flow, I almost threw the heads in the river! But then I thought that's money, if I was going to do anything, I was going to throw one through his shop window, the other through his car window! But I'm not like that, it was a good feeling thinking about it! I ended up fixing them myself!
Top information and correct analysis of real engine flow needs!
Great class thanks
You should put that disclaimer scrolling like star wars at the beginning
Awesome vid Eric. I remember reading the actual "Engine Masters" magazines back in the day. I loved them, because they were so informative for me ,as I was just getting into the "Hot Rod" hobby at that point. It's cool to learn new ways to apply the math and be able to compare in further detail the theroy behind these impressive builds. Thank you.
I really enjoyed this video it made me look at things a little differently 👍
One last question to put a pin in this subject: With an engine where the intake CFM flow is considerably behind the piston's "demanded" CFM, the only way you're making up the deficit is to continue to try to fill the engine as the piston is traveling back up from BDC -and this is how you end up with >100% VE, right? --When the engine is trying to cram more air into the cylinder on the way up -isn't this when the coefficient of discharge is the most important? Wouldn't a faster air/fuel mixture bring with it more pressure to keep filling the cylinder those last few degrees?
Or is this all about PRESSURE differentials and the speed / coefficient of discharge through the valve curtain area not actually matter for cylinder filling when the piston is moving up the bore? (Hmm... An engine's VE is greatest at the TORQUE peak RPM when just happens to be where all these filling variables work the best together in your engine.??..)
Does a larger valve size change the engine's torque peak? If so, up or down in RPM?
Thanks so much man, this helped me answer many questions I had for engineers who couldn’t answer
Coefficient of Discharge by itself is a worthless # until you tie in Cylinder Displacement and RPM into the equation. Coefficient of Discharge only addresses Potential of a Cylinder Head; it doesnt address how a Cylinder Head will behave on different displacements.. Until you qualify how the Cylinder Head sees the Cylinder within RPM, Coefficient of Discharge means nothing. In other words, how does your 220cc Port respond sitting on a 302 V8 vs sitting on top of a 427 V8? What you (we, or all of us) are attempting, is to qualify small, medium, maximum sizing relative to expected mild, medium, maximum output within the category intent of pump gas or race gas in which the engine is suppose to operate in. You are dealing with airflow velocity degrees of efficiencies relative to mild, medium, maximum output at a specific RPM.
Edit: BTW, good video with real numbers, and proper approach to identifying Cylinder Head parameters
You're misunderstanding what discharge coefficient is. It's a simple ratio between two different mass flow rates via the same method of discharge. For example, your stock intake valve flows 262 cfm, your ported intake valve flows 350 cfm, the discharge coefficient is .75:1. What you're referring to is "mass flow rate". That's the rate in which the air enters the combustion chamber by way of the valves cross sectional area. What Tooley was saying is true, if when you are finished with your cylinder heads and the discharge coefficient has increased, they will make more power. Plain and simple.
I wish I could post a picture of the porting book I have from Darin Morgans porting class it has part of what you are saying but it based on max flow at curtain area vs what is possible. In your example just making the port larger making flow more it would make more power. It is more complex than that. Hence using an area formula with it.
@@WeingartnerRacing I never said if you make a port larger it will make more power. What if that giant port has a tiny 1.25" ID valve seat? Now what if you install a 2.5" ID valve seat? You will of course have a discharge coefficient between the two and one will have a higher mass flow rate. The one with the higher mass flow rate has the higher power potential.
@@garykarenmcgruther6386 I have one of those two books coming now. Curious to say the least.
Great Videos. When are those metal rings around the chambers necessary?
Abseloutly spot on. I have several times experienced the same. Like an engine where the piston wanted 250cfm and i could only flow 195 but by fitting a Big valve killing the dc but adding like 15 cfm it made more power all over the curve
If your engine wanted like 190 cfm and you Can flow that with a smaller valve and your dc increase it Will make a lot of more power.
But again there is a lot going into it, sec choke , avg airspeed , peak airspeed , airspeed change over time, CSA , engine aplication and so on.
On a stock sbc vortec head with minor blue printing and a fresh 3 angle cut..
I'm considering throwing the intake valves into the lathe and turning the circumference down.. I know it sounds backwards but the seat and where the valve rides is more than 1, 5mm from the edge on stock valves.. I know the optimum solution would be to port the head to suite the valves and then cut a new 3 angle seat.. But this is for a boat and I'm not going to do that.. I was considering the lathe because it would unshrowd the valve a bit.. But would it improve the airflow?
(I'm considering cutting 0.6 - 0.7mm on the radius)
I am curious about on a 13 degree head, the SSR is tight. What throat percentage do you recommend for a 2.19 / 1.66 valves in a 4.16 Ford FE 428 CJ head? It came with a 2.09/166, but the Medium and High Riser Tunnel Port had up to 2.25 valves in 4.23 bores. If I can find some aluminum heads I’d like to find three so that you can experiment like you did with the LS head, and I wish I had an intake slab cut at the valve cover rail so it would compare with other heads. Jay Brown is developing a 2 piece intake like the old PSE that had a valley to head casting that allowed Cleveland intakes to bolt on. One of those center pieces would be great when doing FE stuff.
Is not the peak coefficient og discharge numbers usually at very low valvelifts? I guess improving the numbers after 0.25D should be beneficial.
Awesome video. Thank you very much!
Please Eric do a video for the Honda K20 heads, I would be grateful.
Enjoy every video so far.
Thanks
I don’t do import heads.
@@WeingartnerRacing
Are the rules the same about valve diameter, valve throat, discharge coefficient etc... Or they are another story?
What was the interruption at 11.47 that was weird great explanation this shows how an engine with bigger valves big camshaft can valve float and make less power
Always learning, thanks, great channel. Only downside, everyone else is learning too. But good for them.
I like that, “With every myth is a little bit of truth mixed in.”
The low lift flows are controlled more by the valve job and valve shape. From off the seat to under .400 lift. I can have a small or a big valve in the same head and the flow will be very simular with the same valvejob. Also I dont go by curtain area as defined. I use gauge pins and lift the valve to a given lift and measure the distance between the valve and the seat. This become important when changing the valve angles. Things like different seat angles and back cuts on the valve can change this area dramatically. Example no back cuts on the valve and a 30 degree seat angle will have far more area between the seat and the valve than a 60 degree with a back angle. Try it and you will see that the steeper the seat for example you will need to lift the valve farther in order to equal the same area as let's say a 45 degree seat angle.
Eric curtain area can be deceiving as it describes the area from valve od on the valve head straight down to the valve seat. However if you take a head , lift the valve let's say .600 lift with a 45 degree valve and measure between the seats, then grind the valve to 60 degree and re-measure you will see what I mean. When you grind the valve to test keep the seat width the same to keep it relevant in comparison
I agree I just didn’t want to get off in the weeds trying to explain cd.
@@WeingartnerRacing , doing a great job
I have a Honda k20 engine. I have 1mm oversized dished valves on the intake and I have stock size flat faced valves on the exhaust side. Is this good?
Would love to see what you can do with a good set of original 906 vortecs with a 2.05 intake valve.
Vortecs aren't a very good head for high lift flow so they wouldn't be the best ported. They are strictly designed for swirl. They make great torque and flow up to about .500 lift and 400hp. But I don't think you'll ever see a ported vortec head that makes 600+hp N/A.
if i have a 2.02 on vn aussie v8 heads and i want the 91 percent throat you say flows the best what size am i looking for please and how do you measure it
hi good afternoon mr Eric I need to know if you can recommend AFR head for 454 Ls for approx 1000 HP. for the sake of the streets and the heads to octimize them "I mean to work the head for you Mr. Eric
Great video!!!
Cool. Very informative.
What are your thoughts of mirror polishing the exhaust port? Or the chamber for that matter? Just crossing over thoughta from porting 2 stroke cylinders to keep the carbon from building up and changing how the engine runs over time.
Huge waste of time. Just sayin.
Hi, I really think BT Is one of the smartest guys!!!! ( I saw him talk about this on the tuner school video) I completely see your point a bigger valve even if not as great is still bigger and could flow more... I have a zl1 1le (lt4) would you just port the stock heads or get something else? BTR cam lifters, push rods trunnion upgrade (rocker arms??) cai, headers, magnuson 2.6 for road racing could not get a stick...so it has a 10 speed thanks
This may be off point but I want to ask about cutting into the head bolt holes, I`ve flowed them before and it doesn`t seem to hurt flow at all but what im concerned about is the integrity of the head. With the use of studs with the fine threads and increased torque the clamping pressure has to be much more than a bolt. A customer had a set of heads done and I`m concerned about crushing the head............ its a BBC aluminum and there`s 2 holes in each head, can I have youre thoughts on this?
I have not had any issues. It’s very common on bbc heads.
Great info!
Cool vid.hi isn't vavle curtain 25% of valve diameter?been porting for a little while everyone does there own things which is cool.when you say a sluggish isn't piston drawing or pulling more air then before which lower mean port velocity or ramming effect compared to standard valve just needs more rpm to create more velocity to get port efficiency.or cam change.ring seal is so important to port co efficiency from overlap to ramming effect hopefully equilibrium between intake charge and cylinder pressure.just that piston doesn't get mentioned much when it comes to porting Imagine doing all that head work and piston ring have to much blow by loss hp.peace
If you look at the shape of the chamber that the valves are in and you have the minimum amount of restriction to the intake valve seat the more power your going to make and the exhaust side of the head even with a smaller valve size as long as it to has minimum restriction to flow it's really about chamber size and shape of the chamber to unshroud the valves and port size that makes the most power. 🤔
Not exactly. You still need restrictions in a port to manage air speed. Otherwise you would have a sewer pipe size hole that flows a metric fuck ton of air, but doesn't make ANY power. More to it than that.
Im kinda new to all of this so it was good to get a good explanation of the fundamentals.
How does exhaust flow come into play in all this? Is it important to power production?
I have that magazine lol
A engine is a very complex system, very dynamic, we may never completely understand what is going on, ya can't always quantify the complex system we call a engine, it's a very complex air pump, it's a pulsing system it's difficult to test that on a flow bench, pulse flow acts different than steady state,,,
Does this apply to generally all BBC heads as well? My brother keeps saying the exhaust is the problem on BBC. I see a lot of big intake valves in BBC makes me think your theory applies to them as well.
Yes. The exhaust valve is too big on most bbc heads.
Good info. I'm glad I didn't find this when I was doing my research before porting my heads as it would have only confused the situation. Ray Mondello claims that 90-91% is way too large for a street head but okay for an all out race head. I put larger valves in my heads because I got up into the 90% range in order to blend sharp edge on the bottom of the seat into the bowls. The +1mm valves brought me back down to about 86% since this is going to be a mostly street driven car. I haven't run the engine yet so we'll see. This was my first port job. I actually just uploaded a video on it if you want to check it out over on my channel. Thanks for the information!!
The throat size knows nothing about street and race. Have tons of customers who drive race cars on the street, should we have two separate heads with small and big throats? It's about air speed and power. 90% is NOT too big for a street engine. Where your minimum cross section is in the port also matters. It is also different for every engine. 86% is too small for an exhaust valve, let alone an intake. And becomes a choke regardless of valve size.
Nothing wrong with following one person who you think is right, but don't feel like you will be confused when someone else does something different. Either way you will learn something, good or bad.
@@jrdmotorsports9718 Thanks for the reply. I'm all ears and all for learning!
I get what you're saying. What came up a lot in my reading was that for low-mid rpm the larger throat sacrifices velocity, and therefore is not the ideal choice for a street driven car. Obviously nobody is gonna swap back and forth between multiple sets of heads depending on how they're driving the car that day. My question was more to say that if a car is predominately street driven is a 90-91% throat too large. I guess what I really was asking is- is it ideal for a street driven vehicle?
I ended up cutting my valves down to +.5mm which brought my throats up to around 88%. I am concerned I didn't open the exhaust ports up enough for the tulip valves I installed, but we'll see. The motor is in the car, just have some wiring stuff to sort out. I'm going to share more on my heads, the ratios I ended up with and the power it made once I get it on the dyno if you care to subscribe and have a look. I'd be happy to hear your thoughts and opinions once we can look at the dyno graph along with the head numbers.
Anyway, I do appreciate the reply. Take care.
@@BradfordsGarage Throat size is relevant to where the MCSA is in the port. The mcsa SHOULD be at the throat, but it isn't in all heads. Most street engines have the mcsa upstream, away from throat, and by making the throat too small doesn't help, regardless of the rpm. With the mcsa at the throat, it is critical to size it correctly to the valve size, which should be sized correctly to the bore size. Then comes curtain area. It's ALL relative. Too small of a throat, becomes a choke and does not aid in velocity at higher rpm, especially when the mcsa is upstream of the port. When mcsa is upstream, and the throat is small, once the venturi convergence are is bigger, air speed starts moving up the throat and causes chaos....
@@jrdmotorsports9718 I see. Well, the dyno will give the final say. I just got the engine fired up yesterday, so will be getting it on the dyno in the next couple of weeks. Thanks again for the reply.
@@BradfordsGarage Actually, the TRACK would give the final say. A dyno, like a flow bench, is just a tool. Tools that CAN and DO lie to you. The car has the final say. Good luck!
Well to jump in on the conversation that I just got about the larger intake valve someone put a 202 in it well I started doing heads around 1980 for about 20 years of it and no flow bench or anything but everybody wanted to get 202 heads and get more power and all that stuff kind of like going from a 650 Holly to a 750 and then going up to an 800 double pump it ruins everything I built a set of small block heads for myself and it since the valves were free! I put it in a set of 39 heads the problem with it is I didn't have any money to buy what I wanted but the LeMans cam I had didn't wake up until four grand with the 194th if I would have put 190 160s in it it would have changed it and the velocity would have changed but again I didn't have a lot of money so I did what I could do but not necessarily bigger is better at least in the mechanical world
Continuity equation from fluid mechanics; Q=VA flow=velocity*area (curtain area/throat area/etc).
You also need to unshroud the bigger valve to take advantage of the larger valve
Yes.
Is there any truth to this ?
The more a head flows closer to piston cfm demand at 65-70 percent of lobe lift , the more power the motor will make ?
(19:29) Maybe need a heatsink on GoPro #engines #badassheads #bossmaneric
I think it was David Vizard who found that using a 1.9 intake with a 1.7 exhaust (a Ford windsor valve I believe) actually flowed better on a forced induction SBC than the commonly held 2.02 / 1.6 . People think its all about intake and getting it out of the engine doesnt matter in the scheme of things, but the dyno proves differently. Its not a 2 stroke people, and thats another totally different can of worms that I wont get into here lol
Probably because he never changed the throat size. It’s only without any other work done besides cutting to larger valve have I seen a larger valve make less power.
One person promoting 50 year old technology or one point of view is not something that is the end all be all... either there is a reason or they may just show you what can happen if you follow their narrative. Certainly not the best way to make power.
Another, rarely scene possibility is the valves is the perfect size for the cam and the cam is the perfect size for compression and cylinder etc etc and now a bigger valve doesn't match the rest of the criteria. Now it's the weakest link of the system because the rest of the system
I think u hit the nail on the head! Something can be important and still not be everything. Kind of like boost, everyone trying to make more boost. Need more boost. Cooler air is many times better than more boost!
Coefficient of discharge also needs to be used with port velocity and port energy. All work together
Somewhat.
Hell Yeah
why dont you do mopar stuff too?
I do it just rarely cones in. The latest video is on a mopar head.
It wasn't you, I would call you out on those valves being shrouded by the cylinder/chamber!
Some shrouding is necessary. Sounds weird right? But true. What you don't want, are valves opening into empty space.
As far as I remember Jon Kasse won more times than Bischoff. I think Kasse won four times?
I Just put in edel e Street. I am about to pull them out and put bigger intake 😂
A bigger valves doesn't always mean more power. Too big on a small port will do nothing. It's all relative.
Your comments at 6:50 are somewhat misleading. You say that the throat of the 2.08 valve is 1.8928 and the throat of the 2.10 valve is smaller at 1.89.
This is physically impossible. Putting a larger valve in doesn't magically reduce the actual physical size of the throat. It only reduces its relative size, as a proportion of the new valve diameter compared to the old valve. Therefore the assertion that the throat diameter becomes smaller is flawed. It must be 1.8928 in both cases so the calculated CSA must remain the same too.
Thanks your the video. Just here to learn a good example of engines is the 302 chev and the 302 ford Cleveland . The ford in my option had a better heads and could get by with less camshaft
This also explains why "on paper" 4 valve engines often seem to have milder cams then a comparable 2 valve engines. Because 4 smaller valves have more area then 2 large valves inside the same cylinder 4 valve engines act like 2 valve engines that have had huge valves installed so any lift, duration, and overlap "acts" bigger.
4 valve engines, I've figured out with messing with cam timing, are much more sensitive to overlap (they don't need as much).
All highly rod ratio , displacement , cam duration , and camshaft LSA SENSITIVE !!!! Easy to get in trouble with shorter strokes , long rod and tthir longer rod ratios , smaller displacements and lower rpm , too much duration and Wide LSAs and not nearly enough cam advancement !!!!
At 13:35 you hit the key point. CD is dimensionless and relative. thus a lower CD on a bigger port can still move more air than a best in class CD on a more modest port. Where CD is really good, is comparing a/b on the same port or bellmouth.
And in real terms anything over 90% is excellent. Though higher CD's are possible on larger ports ;)
😲
The more I learn the more I realize that I DON'T KNOW SHIT!!!!!!
Maybe I've come to a starting point.
that's not the reason Cd isn't as important as Brian would have you believe. keep searching.
👍💪
[2min] Brian Tooley Racing goes over why bigger isn't always better when it comes to the size of your cylinder heads or valves: th-cam.com/video/Qqg3z60ISQo/w-d-xo.html
I get what he is trying to say but when you put a larger valve in most times the low lift flow is better. This keeps coefficient of discharge virtually the same. If it only flows what the smaller valve did then you need to modify things. You also have more area available than the smaller lift. You need more area for higher rpm.
Ur a Master artist, ur drawing had me in laughter.
I have never cared about Cd. It seems like a stupid measure. You will almost never see someone using a smaller valve to increase the coefficient of discharge. It is never successful.
Richard holdener harps on about Cd and often fails to realize that its airflow that makes horses. He has said a bunch of questionable things about gen3 sbc 706/862 heads and how they make power because of the high Cd. When you point out that every single aggressive aftermarket porting package adds larger valves its usually crickets.
Eric, If you have one hour thirty-six minutes, you find this video informative: th-cam.com/video/cgxzjWL8l4k/w-d-xo.html
Legendary engine builder Darin Morgan and Preston Mosher, BES Racing Engines’ cylinder head department manager, dedicated over 90 minutes at the 2021 PRI Trade Show to providing an overview of various combinations built by BES Racing Engines based on 50- to 60-year-old engine architecture utilizing modern cylinder head, induction system, and valvetrain technology to produce ever-higher power levels.
I was there.
@@WeingartnerRacing - Cool.