Mr Vizard. David if I may at after 60yrs old I have been really listening to your videos and have FINALLY had many many ahh moments. You have made all the bits and pieces I had click together like magnets. You remind me of my machine shop teacher from school. You have a way of getting me to actually understand. I can't thank you enough. The years of knowledge you have is beyond my comprehension. Thank you sir. Could I send you a set of brownfield heads to examine and set up a manifold to match?
I couldn't believe that Darin answered my Question about porting a Buick Straight 8 head! He said do the basic work and get the speeds 300 or more on short side in the center of the port I think. But that was important to him!
I seen it actually work that way . During the 80's and early 90's , an old timer racer sold me on this. Everyone was stuck on port flow volume. BBc rectangular heads where 355 cfms and larger. Old timer showed me the way of port velocity of Bbc oval port heads. Oval port velocity flowed better then Rectangular heads. Big heads where high rpms , oval port velocity was better lower to mid rpm. More usable , responsive engine for the street. Also learned smoother ports on intake side was not better. Always great videos.
Come on folks , it seems ... only one in ten viewers are giving a 'like' by hitting the thumbs up . We can do better , yes ? There is no man more deserving than the mighty David Visard and the charitys he serves aswell. ❤. If we help those that help others , the world is a better place. 😊 .Here is a pun ! It is im-port-ant 😂. cheers everyone .
Even though I gave an alternative view I think his approach is solid from the standpoint of he has the data, both bench, dyno, and track to back it up. What ever his use is of terminology the results are the same as some, not many, other engine engineers (not builders, or assemblers). He is rare and a breath of fresh air in the hot rod and high performance arena because he does use science. Others say they do but don’t close the loop like the good Professor Flow (I feel able to make this appointment after the near 40 years in the trenches & spending 10 in night school getting a degree while working, best apprenticeship for engineers, hardly anybody does it). At one time a major OEM in Deeetroit did not have a working flow bench. This was back in the days of getting 105hp out of a 350cid engine. In traditional professional groups we challenge each others works based on our knowledge. It keeps the technology moving. The Professor mentioned CFD. If he embraces it and finds somebody good at it, it is fabulous. All those stream lines are drawn for you. Then you find some going the wrong way and as the professor does die grind the data until it goes away. I ran an analysis group. I should have been reprimanded for all the off topic CFD I did on boat bottoms, propellers, etc. it’s like a kid in a candy store. Good job Professor, take the rest of the day off.
DV can you do a video on induction port and manifold tuning? Ie induction length vs pressure waves, plenum vs no plenum, variable induction systems, etc?
This is impressive. You are proving yourself only at full throttle but your points make even more sense to me when I factor in throttle response where flow is of even less importance than velocity.
Mr. Vizard, I like your idea of velocity lending to "ram" the intake charge into the cylinder. I believe the intake port length of the cylinder head alone is too short in and of itself to allow for this desired ram effect. To enable ram effect, the overall port needs to be lengthened, such as by the design of the intake manifold. The absolute best manifold I have used for this on my small block Chevy is the Smokey Ram SY-1, designed by Smokey Yunick and manufactured by Edelbrock. Careful observation reveals that the intake manifold ports in this manifold utilize (3) aspects of flow to achieve better velocity and flow simultaneously. One, the ports are as long as possible. Two, the ports are as straight as possible with keeping the cylinder head entry angle in line. Three, the port tapers slightly as it approaches the cylinder head entry. This minimizes restriction that just adding length alone would impose. The cylinder does not see the length as causing a restriction, but it benefits from the increased intake port volume which enables the intake ram effect and multiplies its effect at the same time. You have to consider the intake port action from the previous intake valve opening/closing event and how it affects the following one as well. The inertia combined with the efficient (straight and tapered) intake manifold creates the best possible ram effect. Unlike say the Tuned Port Injection design by GM which is not straight and is the same diameter through the tubing instead of progressively increasing in diameter to the plenum, which would have been better. The only improvement that can be made to the SY-1 would be to add port injection to the design to eliminate the wet flow fuel distribution compromise that it currently has. Even so, it runs great and is a way to honor the late Smokey Yunick every time I drive it. Thank you for all you have contributed to our personal attempts to increase our vehicles performance if for no other reason than to have fun and enjoy the hobby or profession as we are able to. God Bless you and yours Mr. Vizard.
I have recently built a single cylinder push rod 2 valve 172cc motorcycle engine. It has had many sessions on the dyno. I have graphs showing the results of reducing the inlet port size at the bowl entry and tapering it all the way to the carb venturi which shows more torque across the range and the motor hanging on to a power increase at the top end for over 1000rpm beyond where it tailed off with the larger port. Increasing velocity works! The engine is currently producing 125 BHP/L which i am quite happy with but i am sure it can make a bit more, which is why i am here to learn from DV! Thank you for sharing your knowledge. I first followed your work back in the 80's helping build an A series 1293 for my brothers Mini, that was an awesome engine! 12G940, BL544 etc.
Built a TE Cortina 250 ci crossflow 6 iron head and followed the principles in Davids Book performance with economy back in the late 80's early 90's. Custom built my own unequal length A/R tuned headers. All I can say. Worked then. And works now. In South Australia the "law" favoured sleeper mods. But being able add more duration & thus overlap without an outrageous lope @ idle is a big bonus for sleepers. I consider what David does is engine development. Not just performance tuning. BIG difference!. That humble engine w hyd flat tappet cam, 2 barrel 350 but 530 cfm flowing modded holley, redline runner matched ported long inlet. Off a wrecked slalem boat motor dyno developed over 10 years Blue printed borg warner 35 4 speed & 3.5 lsd ford 9 in. Ate 5 litre walkinshaw V8's for breakfast. Forgot them for lunch & shat them out in a steaming pile just before dinner was served. Didn't hook up that well till sticky 245's @ low pressure rears assisted & cal track. After that YeeeeeHaaaaa 😂 Bye Bye 🖕 Eat my flatulent burnout vapour! Also passed epa tests BETTER than reg strangulated stock! And highway economy @ 160 kmh AVERAGE was WAY better than any EFI! Research pays dividends. Listen & learn! 🤩 That car was BIG TIME FUN! Light, fast, brutal acceleration AND economical if no lead foot was used. No regrets!
Another very informative video David,. I'm going to get your program and have a play around. Thank you for all the effort you put in. Regards from sunny Essex, Mountune Country 🙂. Chris.
Thanks for your bbc book build hp on a budget. I was always told rectangle ports are the heads to use. So after reading your book I bought afr 265 heads and a camshaft you specd from Terry Walter's. Thanks again. Hope to see more bbc info and watching you and Andy's videos.
So so glad to see all this information from you David, wish I could afford to send you help, but maybe one day, i would not want to forget anything you have taught me 😅 from this video are you suggesting that porting I bigger bowl volume is better than grinding the heck out of the ports? I suspect so, given the velocity coming in from the port fills that bowl area better. I have many more questions but don't want to sound stupid before I understand it better. Your info is gold to me and I am just a sheet metal worker and you have taught me 30yrs of information in one video 😮😀 keep up the good work as long as you can cause we never know when we will go, would feel so privileged if you to acknowledge my comments and thanks from Queensland Australia 🌏
The guy who ported my heads complained about the valve size being too big. He like to see smaller ports and valves than what one normally see on different port videos. He mainly works on engines for professional rally, rallycross etc. Considering Darin Morgans formula for cfm demands one realize that many heads flow more than enough. Thats cid x rpm x 0.0009785/number of cylinders. That works out to a port on a 350 only needing around 256 cfm at 6000 rpm! That means there are a few other factors in play in a head deciding the horsepower other than flow. Things like shape, surface texture, chamber size/design/orientation, etc..
David this would be a fairly easy fix & fill on the 4.8 or 5.3 ls cathedral ports and the truck intake manifold . Nothing is being done with this on these smaller ls engines by Anybody !!! Its throw your wallet at it and forced induction . Big deal !!! Thank you for this tech being made clear . Chevy has made this easy to do . I appreciate your confirmation of my observations on this particular application which is very very similar to your shown example .
It's hard to justify $2500 aftermarket heads (plus intake) that make an extra 40 hp on a 5.3. The gen V heads fix a lot of issues. That's why they make a big, broad torque band (GDI is just a small part of it).
I always try for the best velocity for the usable RPM of the engine combination, which should match its use. Everything has to work together. Even connecting rod length affects airflow requirements. The most common mistake I see in amateur, or even some "gurus", is a completely mismatched combination, such as a 350 Olds engine with stock heads and compression, a hot street cam, with a big single-plane, massive carb, 2" headers, a 5,000 stall convertor and 4:56 gears. I had told the owner what would happen; but he went ahead and as predicted, it came out of the hole like a jack the bear and fell flat on its face because it couldn't rev to use all the high-RPM parts. Another good one was a plow truck 350 Chev engine, which needs low RPM torque. A local shop recommended 882, 76cc head with 2.02 and 1.6 valves, angle milled for more compression, flat-top hypereutectics, an old L79, 350HP, 327 hydraulic cam, a single plane with an 850 double pumper but running exhaust stock manifolds. They also told him the intake side didn't have to be milled after angle-milling the face. Other than the compression increase, everything else was high-RPM, not low RPM torque.
hello engine master... i would like to know more on the aspec of F1 style high port velocity up to point of port flow saturation. especially for 2valve "hemi style" cylinder head. (either straight top-bottom valve position and or offset "swirl" type of valve position) this is because i often doing motorcycle road-course racing that were lower displacement (100cc~150cc single cylinder 2valve 4stroke engine) we often rev them up to 14,000rpm regularly...and trying to find best port configuration/method to reach that saturation point of intake flow (we ran performance D-shaped slide with powerjet carburator) i hope u can come up with that F1 style port velocity/configuration video in future.. such a gem and very much thank you for sharing all of these your expertise/experience. thank you again.. *side note: we make around 140/160hp per Liter of displacement (about 14-16 wheel HP on chassis dyno for 100cc engine specs) **with about 9-11mm of max actual valve lift (depends on cyl head valve size, compression ratio and circuit layout) ***static CR range around 13:1~15:1 (also depends on other engine parameter and circuit layout)
You have to match port velocity to flow to match the cam profile. If the head has a high flow rate the velocity will be slower. To slow a velocity will cause the fuel to separate from the air and create puddling in the combustion chamber. It gets down to this. At what RPM band do you need the power to occur? Then work backwards from there. We used to do this with paper and pen before desktop dyno. Back then Floppy Disks were the $#1t. It's the same math as calculating optimal AR ratio.
@David Vizard. Good stuff! How important is it to flow good numbers past your intended highest lift point? I see porters checking numbers at 1 inch of valve lift on heads that will only see .600" lift. If the port loses 10cfm of flow .050" past your cam's delivered lift is that really important? I'd think developing the head to maximize efficiency within it's intended lift range would be most important?
On the street (some strip action), sustained velocity will enable a wider power and. That's why on big block Chevy s oval port heads are always the better choice for the street.
I use the formula to calculate the peak power rpm, and get a very low rpm value. If I use the volume for 1 cylinder instead of the total volume, the calculation seems correct.
Whatever happened to desmondromic valves? I know Ducati uses them but overall seems like a great way to restore horsepower lost due to turning spring loaded camshaft.
I was taught in engineering school that mass flow = density of material x velocity of the flow x area. Each term is equal, no one parameter dominates unless one of the parameters is more easily varied than another. In intakes of an internal combustion engine the density of the material is fixed, the velocity as the speaker says is all important but how do you control velocity, supercharging, turbocharging, longer runner length to gain momentum, the last parameter is area which is what they speaker is also lumping into velocity by manipulating area. So it’s a combination of area and velocity working together, not one more than the other. I maybe missing the point that area is harder to change than velocity but the velocity is being changed by hacking up the port. Remove any material you changed the area, so you are back to area and velocity working together. The flow vectors are theoretical. The measurements are true. The velocity vectors and port shape are the cause for improved flow but as if it’s due to the vectors shown remain to be seen until a computational fluid dynamic analysis is made. I don’t want to minimize the man’s ability to improve flow but his explanation of the geometric reasoning requires advanced analysis. Don’t jump on my case, jump on the case of the phd’s that write text books on gas and fluid flow. Port energy for steady state flow may not be applicable. Mixing 1/2 MV squared for rigid objects, not gases or fluids. I pretty sure you can’t mix the two. Come on guys that slogged through this stuff let hear some alternatives. The statement that a port that has better flow but at lower energy means that when less gas and air gets into a combustion chamber it will release more energy. That defies a bunch of laws of physics. The energy comes from the fuel air mixture. The more you put in the more you get out. This is bound to open a can of trouble. I’m about the same age as the speaker. Not some punk ass kid just out of E school. I got my 38 years in so I got a few creds.
By changing the contour of the runners you can funnel air to increase velocity higher velocity will for one mix and atomize with fuel better but will also enter into the cylinder at higher speed and can literally go so fast that it can literally cause a positive pressure in the cylinder once the intake valve closes even before the piston starts compressing it. I know that high volume setups can make big power with big money and high stall speeds but I have always had to live within a budget and velocity has always been my best friend.
You may need to rewatch the video or you have mis-stated something in your comment....I’m 26 years out of engineering school and it all makes sense. He has to explain it in non-engineering terms or very few will understand it!
You have neglected the main detail of port velocity, that is the pressure differential between the bore and the areas of the port, that dictates what peak velocity will be within the port in a running engine. This is why you start with a cfm demand calculation to then calculate the minimum cross sectional area of the port, then when tested on the flowbench, the cfm number in relation to the minimum cross sectional area will give you the efficiency of that area, that will also tell you the average airspeed of that area. The minimum cross sectional area is the limiting factor to peak flow. Peak flow is the limiting factor to peak power rpm, airspeed at peak rpm at peak piston speed (which is around 75 degrees after TDC) is dictated by the pressure differential created by the peak piston speed vs the minimum areas of the port, the port size is the restriction that creates the pressure differential that dictates peak airspeeds.
@@hotrodray6802 yes he is but a cylinder head port can flow more cfm and have the same velocity on a flowbench, that is just a factor of efficiency through the area. What you need to know is the port cfm demand at your desired peak rpm point to calculate the minimum area required to keep peak airspeeds in between 615-670fps in the running engine, this will avoid subsonic choke if the air column is stable.
@@hotrodray6802 I can have a port flow 200cfm at a 330fps average on the flowbench, I can also have a port that flows 400cfm at a 330fps average on a flowbench, which one suits your application? That is where cfm demand is needed.
No, you really, really, oversimplified that. Quit trying to get a gotcha moment and quit while you're ahead. Why don't you take a few seconds and realize what it takes to quantify the pressure differential during an induction event then chill. This has actually been covered many other times in David Vizards other works dating back decades. Once you have read and memorized it all come back.
Why is head flow measured with a fan that continuously sucks air, wouldn't the measurement be more accurate if a reciprocating pump was doing the sucking and blowing?
Great question. Most testing is an attempt to approximate what happens in reality. Whether its a flow bench, an engine dyno, or a chassis dyno - they're not quite the same as real world operation. We simulate and then compare with reality and hope our approximation is close enough. CFD software lets us get a lot closer in many ways, but I'd love to see true flow measurements with the stopping and starting of air in the port like in a real engine. I'd suggest purchasing an SAE membership and start searching their papers. There are a lot of good research papers in the library and some cover topics like this.
You need to obtain and read DV's book, Porting and Flowtesting heads. He discusses his David Vizard really cheap flow bench. When testing flow on a flow bench, you are looking for and documenting the flow profile to compare whether you are improving or harming the flow. Using a standard pressure drop allows comparing different head ports. To get, as Paul Harvet used to say, "and now for the rest of the story", you need DV's head porting and flow testing book.
Artificial Intelligence snd Generative Design will completely change the design of our ports and change everything we understand or at least envision of an effective port shape and design. The current designs coming from AI already look alien and flow incredibly better then traditional human designs. I seem a port done in an IBM and HP joint project that resembles a cylinder head port and the most efficient port actually breaks the passage way into multiple smaller ports at points and even had what resembled a long curved human tongue in the dang port. This design flowed over 150% better and more efficient then our current port designs.
There have been plenty of bbc dyno tests with rectangular versus peanut port. At low to mid range the peanut always left the rectangular behind by lots with a 600 hp build. Velocity wins. Sure big revs and hp need more area
Velocity Some back pressure is needed to regulate valve lash . But too much from turns in exhaust pipes create pressure . Every 90 degree turn adds 100 ft of straight pipe back pressure . Some trucks I crunched had tail pipes equaling 104 ft in straight pipe back pressure . Nice vid
How is port volume measured and how can it be used to compare different engine families? If all you’re working on is SmallBlock Chevys port volume could be used to determine the right hand for the job. Now compare that to a Ford FE head which has a much shorter intake port than the SBC, and tell me how you can compare the heads four the two engines. Even comparing an SBC to a Mopar LA engine won’t work because the Mopar’s valves are centered in the combustion chamber and the Chevy is not. It seem like somebody took a term and started throwing it around like rating car speakers in watts instead of efficiency.
Very interesting way of solving tight turn of downdraft manifold to horizontal port! I thought that enlarging bowl helps slow down air in order to minimize flow separation at short side of corner🤔
But there is a third part to this concept. Pressure. Do not think of the obvious. I am not speaking of the obvious turbos, blowers, altitude. The MOMENT an intake valve opens, what if you could have a pulse of pressure that started then, and lasted as long as you needed it to, then disappeared the moment the valve shut, to encourage fresh charge to fill the area again? WHAT IF YOUR PORTS BREATHED? THINK OF THIS. Everyone assumes the intake tract has to stay one size at all times. Your lungs, etc. do not. Why not ports that breathe as necessary?
Higher speed ports have less reversion. Jam packing the port. The sooner the ram effect can accumulate in the bowl. Ammunition. Faster speeds have higher impact energy. Weight is how long it holds onto the energy.
Clear lacking within proper basic physics ! :-) F = mass x acceleration = mass x velocity ^2 /2 => Energy Your attempted claim with mass of the projectile, bullet within the stability of travel through the air. Also, the shape of the traveling mass, projectile is affected by air resistance, friction which are also called drag within aerodynamics. All The Best, Sincerely Note: Proper basics, principles, knowledge are important, essential, vital, critical as David Vizard has.
This is exactly why I don't like those FIA nissan l series heads. Way too much port for the valve, however what seems obvious to me seems to overridden by the religious belief of others :)
HEY DAVID, there seems to be alot of , lets say misled people on youtube and here in canada. Every body puts Dual 2.5 or even dual 3 inch exhausts on everything from stock 4.8 L Ls, 1995 366 bus engines to stock 325 2004 truck engines. Seems to me a SINGLE 3 inch mandrel bent system should suffice for most these lower power stock engines. I seen a chart somewhere saying about 1 inch of mandrel bent pipe /100hp is a good ballpark estimate and only a dyno will rweally tell you if you need more BUT common sense should dctate a relatively stock engine thats run 99%on the strreet should be good with a single 3 inch AM i CORRECT or are they actually benefitting from DUAL 3 INCH[besides their egos]
the reason i ask is im considering buy the old 1960 apache with 1995 bus engine in it. its stock engine with less than130,000 miles BUT he has dual 2.5 mufflers on there/ He also says theres a header flange problem that needs fixing so while i am it fixing that , should i just delete an entire muffler and tailpipe and just ypipe them together? Stock power is about 230 Hp, 385 Tq
If you read MacInnes' turbo book, he talks more about density than boost. Turbos and centrifugal SCs are making density in the volute. They don't really jam the air in the engine. That's why you can get compressor surge. They mostly work the same as NA. The wave speed changes however. With a positive displacement blower, it probably can make an increase in velocity since it is pumping air.
Here’s my argument based on my dyno data on late model fuel injected Harley’s using throttle by wire. port velocity on such a short intake runner length using electronic throttle is no longer a concern as the throttle blade or velocity valve as I like to call it can be mapped to maintain peak air speeds at all accelerator positions or torque requests. As for the 170 port vs 195 port , for that specific cam timing the 170 was better, but change the cam timing to take better advantage of the 195 and my bet is you will make even more power correct ? the more we increase flow the less time we need to hold the valves open so the piston does more work .
Place an electric diagonal fan on top of a piston in an operating cylinder. When the piston is at BDC on the intake stroke, the diagonal fan will generate a lower pressure area on top of the piston attracting air to flow into the cylinder through the intake valve even though the piston is rounding BDC and moving toward TDC. The spinning fan will obviously encourage air to flow into the cylinder until the intake valve closes. Remove the diagonal fan and replace it with high velocity swirl energy generated by a purposely designed intake port and it will act exactly like the diagonal fan and allow air to enter the cylinder by increasing the velocity and lowering the air pressure even though the piston is moving toward TDC until the intake valve closes. As opposed to a lazy/large flow/low velocity port with no swirl energy that allows the air pressure in the cylinder to equalize with manifold pressure at BDC and the rising piston will simply push all of the air previously captured, back into the intake port before the intake valve is closed. No ram effect, no volumetric efficiency, no power. ☺
I've read your SBC book enough times over several years I needed to duct tape the cover. All while buying many recommended parts and brands along with your spec cam from Lunati, I'm very pleased, did the go, now time for the show. But DV, you have to do something about these full length ads and not being able to skip after 5-15 seconds, please!!!
I haven’t watched the video yet but here is my thinking. For torque go with velocity (pack the cylinder early). For max HP go with FLOW. The more air = more fuel = more HP. So, now I’ll watch and see if I’m right.
Im peggys hubby,.. I have learned a lot from all your vids. Thanks !!
Thank you Mr. David Vizard for sharing your experience and knowledge!
Thank you DV, I very much enjoy your videos
Mr Vizard. David if I may at after 60yrs old I have been really listening to your videos and have FINALLY had many many ahh moments. You have made all the bits and pieces I had click together like magnets. You remind me of my machine shop teacher from school. You have a way of getting me to actually understand. I can't thank you enough. The years of knowledge you have is beyond my comprehension. Thank you sir. Could I send you a set of brownfield heads to examine and set up a manifold to match?
I couldn't believe that Darin answered my Question about porting a Buick Straight 8 head! He said do the basic work and get the speeds 300 or more on short side in the center of the port I think. But that was important to him!
Thanks DV and company.
And company lol.
Thank dv❤
I seen it actually work that way . During the 80's and early 90's , an old timer racer sold me on this. Everyone was stuck on port flow volume. BBc rectangular heads where 355 cfms and larger. Old timer showed me the way of port velocity of Bbc oval port heads. Oval port velocity flowed better then Rectangular heads. Big heads where high rpms , oval port velocity was better lower to mid rpm. More usable , responsive engine for the street. Also learned smoother ports on intake side was not better.
Always great videos.
Come on folks , it seems ... only one in ten viewers are giving a 'like' by hitting the thumbs up . We can do better , yes ? There is no man more deserving than the mighty David Visard and the charitys he serves aswell. ❤. If we help those that help others , the world is a better place. 😊 .Here is a pun ! It is im-port-ant 😂. cheers everyone .
Even though I gave an alternative view I think his approach is solid from the standpoint of he has the data, both bench, dyno, and track to back it up. What ever his use is of terminology the results are the same as some, not many, other engine engineers (not builders, or assemblers). He is rare and a breath of fresh air in the hot rod and high performance arena because he does use science. Others say they do but don’t close the loop like the good Professor Flow (I feel able to make this appointment after the near 40 years in the trenches & spending 10 in night school getting a degree while working, best apprenticeship for engineers, hardly anybody does it). At one time a major OEM in Deeetroit did not have a working flow bench. This was back in the days of getting 105hp out of a 350cid engine. In traditional professional groups we challenge each others works based on our knowledge. It keeps the technology moving. The Professor mentioned CFD. If he embraces it and finds somebody good at it, it is fabulous. All those stream lines are drawn for you. Then you find some going the wrong way and as the professor does die grind the data until it goes away. I ran an analysis group. I should have been reprimanded for all the off topic CFD I did on boat bottoms, propellers, etc. it’s like a kid in a candy store. Good job Professor, take the rest of the day off.
DV can you do a video on induction port and manifold tuning? Ie induction length vs pressure waves, plenum vs no plenum, variable induction systems, etc?
Thanks again for the great information on cylinder head ports and manifolds.
A living legand! Thank you Dave I love what you share . I had to learn velocity and efficiency in ports on a 4 stroke the hard way
This is impressive. You are proving yourself only at full throttle but your points make even more sense to me when I factor in throttle response where flow is of even less importance than velocity.
Mr. Vizard, I like your idea of velocity lending to "ram" the intake charge into the cylinder. I believe the intake port length of the cylinder head alone is too short in and of itself to allow for this desired ram effect. To enable ram effect, the overall port needs to be lengthened, such as by the design of the intake manifold. The absolute best manifold I have used for this on my small block Chevy is the Smokey Ram SY-1, designed by Smokey Yunick and manufactured by Edelbrock. Careful observation reveals that the intake manifold ports in this manifold utilize (3) aspects of flow to achieve better velocity and flow simultaneously. One, the ports are as long as possible. Two, the ports are as straight as possible with keeping the cylinder head entry angle in line. Three, the port tapers slightly as it approaches the cylinder head entry. This minimizes restriction that just adding length alone would impose. The cylinder does not see the length as causing a restriction, but it benefits from the increased intake port volume which enables the intake ram effect and multiplies its effect at the same time. You have to consider the intake port action from the previous intake valve opening/closing event and how it affects the following one as well. The inertia combined with the efficient (straight and tapered) intake manifold creates the best possible ram effect. Unlike say the Tuned Port Injection design by GM which is not straight and is the same diameter through the tubing instead of progressively increasing in diameter to the plenum, which would have been better. The only improvement that can be made to the SY-1 would be to add port injection to the design to eliminate the wet flow fuel distribution compromise that it currently has. Even so, it runs great and is a way to honor the late Smokey Yunick every time I drive it.
Thank you for all you have contributed to our personal attempts to increase our vehicles performance if for no other reason than to have fun and enjoy the hobby or profession as we are able to. God Bless you and yours Mr. Vizard.
Thanks! It's in the Velocity! Very good !
I like the quote from Darin Morgan I’m a velocity manager not a head porter!
I have recently built a single cylinder push rod 2 valve 172cc motorcycle engine. It has had many sessions on the dyno. I have graphs showing the results of reducing the inlet port size at the bowl entry and tapering it all the way to the carb venturi which shows more torque across the range and the motor hanging on to a power increase at the top end for over 1000rpm beyond where it tailed off with the larger port. Increasing velocity works! The engine is currently producing 125 BHP/L which i am quite happy with but i am sure it can make a bit more, which is why i am here to learn from DV!
Thank you for sharing your knowledge. I first followed your work back in the 80's helping build an A series 1293 for my brothers Mini, that was an awesome engine! 12G940, BL544 etc.
Audio Quality is great in this episode, keep on getting better!
Built a TE Cortina 250 ci crossflow 6 iron head and followed the principles in Davids Book performance with economy back in the late 80's early 90's. Custom built my own unequal length A/R tuned headers. All I can say. Worked then. And works now.
In South Australia the "law" favoured sleeper mods. But being able add more duration & thus overlap without an outrageous lope @ idle is a big bonus for sleepers. I consider what David does is engine development. Not just performance tuning. BIG difference!. That humble engine w hyd flat tappet cam, 2 barrel 350 but 530 cfm flowing modded holley, redline runner matched ported long inlet. Off a wrecked slalem boat motor dyno developed over 10 years Blue printed borg warner 35 4 speed & 3.5 lsd ford 9 in.
Ate 5 litre walkinshaw V8's for breakfast. Forgot them for lunch & shat them out in a steaming pile just before dinner was served. Didn't hook up that well till sticky 245's @ low pressure rears assisted & cal track. After that YeeeeeHaaaaa 😂 Bye Bye 🖕 Eat my flatulent burnout vapour! Also passed epa tests BETTER than reg strangulated stock! And highway economy @ 160 kmh AVERAGE was WAY better than any EFI! Research pays dividends. Listen & learn! 🤩 That car was BIG TIME FUN! Light, fast, brutal acceleration AND economical if no lead foot was used. No regrets!
Thank you David and Andy
Another very informative video David,. I'm going to get your program and have a play around. Thank you for all the effort you put in. Regards from sunny Essex, Mountune Country 🙂. Chris.
I've a couple intake manifolds I need to port and one I need to build from scratch. This information will be quite use full!
Thanks for your bbc book build hp on a budget. I was always told rectangle ports are the heads to use. So after reading your book I bought afr 265 heads and a camshaft you specd from Terry Walter's. Thanks again. Hope to see more bbc info and watching you and Andy's videos.
So so glad to see all this information from you David, wish I could afford to send you help, but maybe one day, i would not want to forget anything you have taught me 😅 from this video are you suggesting that porting I bigger bowl volume is better than grinding the heck out of the ports? I suspect so, given the velocity coming in from the port fills that bowl area better. I have many more questions but don't want to sound stupid before I understand it better. Your info is gold to me and I am just a sheet metal worker and you have taught me 30yrs of information in one video 😮😀 keep up the good work as long as you can cause we never know when we will go, would feel so privileged if you to acknowledge my comments and thanks from Queensland Australia 🌏
Another jewel found only here. Much thanks.
The guy who ported my heads complained about the valve size being too big.
He like to see smaller ports and valves than what one normally see on different port videos.
He mainly works on engines for professional rally, rallycross etc.
Considering Darin Morgans formula for cfm demands one realize that many heads flow more than enough.
Thats cid x rpm x 0.0009785/number of cylinders.
That works out to a port on a 350 only needing around 256 cfm at 6000 rpm!
That means there are a few other factors in play in a head deciding the horsepower other than flow.
Things like shape, surface texture, chamber size/design/orientation, etc..
David this would be a fairly easy fix & fill on the 4.8 or 5.3 ls cathedral ports and the truck intake manifold .
Nothing is being done with this on these smaller ls engines by Anybody !!! Its throw your wallet at it and forced induction . Big deal !!!
Thank you for this tech being made clear . Chevy has made this easy to do . I appreciate your confirmation of my observations on this particular application which is very very similar to your shown example .
It's hard to justify $2500 aftermarket heads (plus intake) that make an extra 40 hp on a 5.3. The gen V heads fix a lot of issues. That's why they make a big, broad torque band (GDI is just a small part of it).
The new Canted Valve Cathedral port heads, from BTR (Brian Tooley) are exceptional heads, they can hold their own against an LS7 head, easily
Thanks for sharing all of your hard work!
A video on making flow better thru transitions would be very valuable. 😀
What a wealth of info!!!!
Thank you.
Awesome video
Good information as always Sir 👍.
I always try for the best velocity for the usable RPM of the engine combination, which should match its use. Everything has to work together. Even connecting rod length affects airflow requirements.
The most common mistake I see in amateur, or even some "gurus", is a completely mismatched combination, such as a 350 Olds engine with stock heads and compression, a hot street cam, with a big single-plane, massive carb, 2" headers, a 5,000 stall convertor and 4:56 gears. I had told the owner what would happen; but he went ahead and as predicted, it came out of the hole like a jack the bear and fell flat on its face because it couldn't rev to use all the high-RPM parts.
Another good one was a plow truck 350 Chev engine, which needs low RPM torque. A local shop recommended 882, 76cc head with 2.02 and 1.6 valves, angle milled for more compression, flat-top hypereutectics, an old L79, 350HP, 327 hydraulic cam, a single plane with an 850 double pumper but running exhaust stock manifolds. They also told him the intake side didn't have to be milled after angle-milling the face. Other than the compression increase, everything else was high-RPM, not low RPM torque.
Brilliant - thanks for that explanation.
Awesome videos David
Thanks DV
hello engine master...
i would like to know more on the aspec of F1 style high port velocity up to point of port flow saturation.
especially for 2valve "hemi style" cylinder head. (either straight top-bottom valve position and or offset "swirl" type of valve position)
this is because i often doing motorcycle road-course racing that were lower displacement (100cc~150cc single cylinder 2valve 4stroke engine)
we often rev them up to 14,000rpm regularly...and trying to find best port configuration/method to reach that saturation point of intake flow (we ran performance D-shaped slide with powerjet carburator)
i hope u can come up with that F1 style port velocity/configuration video in future..
such a gem and very much thank you for sharing all of these your expertise/experience.
thank you again..
*side note: we make around 140/160hp per Liter of displacement (about 14-16 wheel HP on chassis dyno for 100cc engine specs)
**with about 9-11mm of max actual valve lift (depends on cyl head valve size, compression ratio and circuit layout)
***static CR range around 13:1~15:1 (also depends on other engine parameter and circuit layout)
More great stuff! Thank you DV
Great video as always
Very interesting stuff, thank-you!
BTW I really like your shows.
You have to match port velocity to flow to match the cam profile.
If the head has a high flow rate the velocity will be slower. To slow a velocity will cause the fuel to separate from the air and create puddling in the combustion chamber.
It gets down to this. At what RPM band do you need the power to occur? Then work backwards from there.
We used to do this with paper and pen before desktop dyno. Back then Floppy Disks were the $#1t.
It's the same math as calculating optimal AR ratio.
You're the man brother.
Realy informative. Thanks.
Hello david, Is there any truth in putting dimples in port walls .?
Ok David,360 fpm =peak at 6900 on a 363 cid , do you agree, you will last, you love helping people as do i, thanks for reinforcing my beliefs!!
@David Vizard. Good stuff! How important is it to flow good numbers past your intended highest lift point? I see porters checking numbers at 1 inch of valve lift on heads that will only see .600" lift. If the port loses 10cfm of flow .050" past your cam's delivered lift is that really important? I'd think developing the head to maximize efficiency within it's intended lift range would be most important?
On the street (some strip action), sustained velocity will enable a wider power and. That's why on big block Chevy s oval port heads are always the better choice for the street.
DV
Could you measure a port efficiency by the load pulling the valve down when on a flow bench? Load versus flow?
Just curious as to what % you like to see for the bowl area to valve ratio too please
I think he's mentioned in other videos 87 - 89% for street motors, and up to 91% for racing.
@383mazda for the throat yes but the bowl is larger.
Where can I find your Motortec Features? I'm not having any luck finding it.
I use the formula to calculate the peak power rpm, and get a very low rpm value. If I use the volume for 1 cylinder instead of the total volume, the calculation seems correct.
what would happen if you make the bottom part of that intake straight instead of making it the way you have it on the pic
DV, you need a "mic" pinned to your shirt collar.
Sounds like domestic vile lengths,
Whatever happened to desmondromic valves? I know Ducati uses them but overall seems like a great way to restore horsepower lost due to turning spring loaded camshaft.
I wonder how much turbo's accelerate air velocity into the heads, as opposed to being only mass/density devices?
I was taught in engineering school that mass flow = density of material x velocity of the flow x area. Each term is equal, no one parameter dominates unless one of the parameters is more easily varied than another. In intakes of an internal combustion engine the density of the material is fixed, the velocity as the speaker says is all important but how do you control velocity, supercharging, turbocharging, longer runner length to gain momentum, the last parameter is area which is what they speaker is also lumping into velocity by manipulating area. So it’s a combination of area and velocity working together, not one more than the other. I maybe missing the point that area is harder to change than velocity but the velocity is being changed by hacking up the port. Remove any material you changed the area, so you are back to area and velocity working together. The flow vectors are theoretical. The measurements are true. The velocity vectors and port shape are the cause for improved flow but as if it’s due to the vectors shown remain to be seen until a computational fluid dynamic analysis is made. I don’t want to minimize the man’s ability to improve flow but his explanation of the geometric reasoning requires advanced analysis. Don’t jump on my case, jump on the case of the phd’s that write text books on gas and fluid flow. Port energy for steady state flow may not be applicable. Mixing 1/2 MV squared for rigid objects, not gases or fluids. I pretty sure you can’t mix the two. Come on guys that slogged through this stuff let hear some alternatives. The statement that a port that has better flow but at lower energy means that when less gas and air gets into a combustion chamber it will release more energy. That defies a bunch of laws of physics. The energy comes from the fuel air mixture. The more you put in the more you get out. This is bound to open a can of trouble. I’m about the same age as the speaker. Not some punk ass kid just out of E school. I got my 38 years in so I got a few creds.
By changing the contour of the runners you can funnel air to increase velocity higher velocity will for one mix and atomize with fuel better but will also enter into the cylinder at higher speed and can literally go so fast that it can literally cause a positive pressure in the cylinder once the intake valve closes even before the piston starts compressing it. I know that high volume setups can make big power with big money and high stall speeds but I have always had to live within a budget and velocity has always been my best friend.
You may need to rewatch the video or you have mis-stated something in your comment....I’m 26 years out of engineering school and it all makes sense. He has to explain it in non-engineering terms or very few will understand it!
@@trailerparkcryptoking5213 agreed
You have neglected the main detail of port velocity, that is the pressure differential between the bore and the areas of the port, that dictates what peak velocity will be within the port in a running engine.
This is why you start with a cfm demand calculation to then calculate the minimum cross sectional area of the port, then when tested on the flowbench, the cfm number in relation to the minimum cross sectional area will give you the efficiency of that area, that will also tell you the average airspeed of that area.
The minimum cross sectional area is the limiting factor to peak flow. Peak flow is the limiting factor to peak power rpm, airspeed at peak rpm at peak piston speed (which is around 75 degrees after TDC) is dictated by the pressure differential created by the peak piston speed vs the minimum areas of the port, the port size is the restriction that creates the pressure differential that dictates peak airspeeds.
I'm pretty sure DV is referring to testing at the usual 28" to determine these velocities.
@@hotrodray6802 yes he is but a cylinder head port can flow more cfm and have the same velocity on a flowbench, that is just a factor of efficiency through the area.
What you need to know is the port cfm demand at your desired peak rpm point to calculate the minimum area required to keep peak airspeeds in between 615-670fps in the running engine, this will avoid subsonic choke if the air column is stable.
@@hotrodray6802 I can have a port flow 200cfm at a 330fps average on the flowbench, I can also have a port that flows 400cfm at a 330fps average on a flowbench, which one suits your application? That is where cfm demand is needed.
No, you really, really, oversimplified that. Quit trying to get a gotcha moment and quit while you're ahead. Why don't you take a few seconds and realize what it takes to quantify the pressure differential during an induction event then chill. This has actually been covered many other times in David Vizards other works dating back decades. Once you have read and memorized it all come back.
@@shaunobrien6425 thanks for your input, I feel I have a pretty good grasp on how the induction system works 👍
Why is head flow measured with a fan that continuously sucks air, wouldn't the measurement be more accurate if a reciprocating pump was doing the sucking and blowing?
Great question. Most testing is an attempt to approximate what happens in reality. Whether its a flow bench, an engine dyno, or a chassis dyno - they're not quite the same as real world operation. We simulate and then compare with reality and hope our approximation is close enough. CFD software lets us get a lot closer in many ways, but I'd love to see true flow measurements with the stopping and starting of air in the port like in a real engine. I'd suggest purchasing an SAE membership and start searching their papers. There are a lot of good research papers in the library and some cover topics like this.
I see your science, looks like they would have a replica engine to hook it to
I see your science looks like someone would have invented an engine simulator. I'm not technically advanced. May not be easy to measure that way
Consider the accepted 28" is about 1 psi.
High performance engines when running can do 100 or more NA.
28 is used as a COMPARISON.
You need to obtain and read DV's book, Porting and Flowtesting heads. He discusses his David Vizard really cheap flow bench. When testing flow on a flow bench, you are looking for and documenting the flow profile to compare whether you are improving or harming the flow. Using a standard pressure drop allows comparing different head ports.
To get, as Paul Harvet used to say, "and now for the rest of the story", you need DV's head porting and flow testing book.
Artificial Intelligence snd Generative Design will completely change the design of our ports and change everything we understand or at least envision of an effective port shape and design. The current designs coming from AI already look alien and flow incredibly better then traditional human designs. I seem a port done in an IBM and HP joint project that resembles a cylinder head port and the most efficient port actually breaks the passage way into multiple smaller ports at points and even had what resembled a long curved human tongue in the dang port. This design flowed over 150% better and more efficient then our current port designs.
Thanks!
Tack!
There have been plenty of bbc dyno tests with rectangular versus peanut port.
At low to mid range the peanut always left the rectangular behind by lots with a 600 hp build.
Velocity wins.
Sure big revs and hp need more area
🚀🚀🚀
I’m ready for some more small block Ford cylinder head tricks 👍🏻
Love your wisdom thank you. Like to meet you one day brother I drove car 50 94 - 2001 ODS
Velocity Some back pressure is needed to regulate valve lash . But too much from turns in exhaust pipes create pressure . Every 90 degree turn adds 100 ft of straight pipe back pressure . Some trucks I crunched had tail pipes equaling 104 ft in straight pipe back pressure . Nice vid
so much to lern
After 350ft per second, you're in the realm of compressibility the flow starts fighting itself.
How is port volume measured and how can it be used to compare different engine families? If all you’re working on is SmallBlock Chevys port volume could be used to determine the right hand for the job. Now compare that to a Ford FE head which has a much shorter intake port than the SBC, and tell me how you can compare the heads four the two engines. Even comparing an SBC to a Mopar LA engine won’t work because the Mopar’s valves are centered in the combustion chamber and the Chevy is not. It seem like somebody took a term and started throwing it around like rating car speakers in watts instead of efficiency.
What's your other channel?
Nothing better only no2
Im going to try a couple hair dryers.
Very interesting way of solving tight turn of downdraft manifold to horizontal port! I thought that enlarging bowl helps slow down air in order to minimize flow separation at short side of corner🤔
But there is a third part to this concept.
Pressure.
Do not think of the obvious. I am not speaking of the obvious turbos, blowers, altitude.
The MOMENT an intake valve opens, what if you could have a pulse of pressure that started then, and lasted as long as you needed it to, then disappeared the moment the valve shut, to encourage fresh charge to fill the area again?
WHAT IF YOUR PORTS BREATHED?
THINK OF THIS.
Everyone assumes the intake tract has to stay one size at all times. Your lungs, etc. do not.
Why not ports that breathe as necessary?
port velocity!
British people say, Lbs. Feet ..Americans say Foot Lbs., even my old torque wrench says, Foot Pounds .
Higher speed ports have less reversion. Jam packing the port. The sooner the ram effect can accumulate in the bowl.
Ammunition. Faster speeds have higher impact energy. Weight is how long it holds onto the energy.
Clear lacking within proper basic physics ! :-)
F = mass x acceleration = mass x velocity ^2 /2 => Energy
Your attempted claim with mass of the projectile, bullet within the stability of travel through the air. Also, the shape of the traveling mass, projectile is affected by air resistance, friction which are also called drag within aerodynamics.
All The Best, Sincerely
Note: Proper basics, principles, knowledge are important, essential, vital, critical as David Vizard has.
This is exactly why I don't like those FIA nissan l series heads. Way too much port for the valve, however what seems obvious to me seems to overridden by the religious belief of others :)
HEY DAVID, there seems to be alot of , lets say misled people on youtube and here in canada.
Every body puts Dual 2.5 or even dual 3 inch exhausts on everything from stock 4.8 L Ls, 1995 366 bus engines to stock 325 2004 truck engines.
Seems to me a SINGLE 3 inch mandrel bent system should suffice for most these lower power stock engines.
I seen a chart somewhere saying about 1 inch of mandrel bent pipe /100hp is a good ballpark estimate and only a dyno will rweally tell you if you need more
BUT common sense should dctate a relatively stock engine thats run 99%on the strreet should be good with a single 3 inch
AM i CORRECT or are they actually benefitting from DUAL 3 INCH[besides their egos]
the reason i ask is im considering buy the old 1960 apache with 1995 bus engine in it. its stock engine with less than130,000 miles BUT he has dual 2.5 mufflers on there/
He also says theres a header flange problem that needs fixing so while i am it fixing that , should i just delete an entire muffler and tailpipe and just ypipe them together?
Stock power is about 230 Hp, 385 Tq
Does boost help velocity?
If you read MacInnes' turbo book, he talks more about density than boost. Turbos and centrifugal SCs are making density in the volute. They don't really jam the air in the engine. That's why you can get compressor surge. They mostly work the same as NA. The wave speed changes however. With a positive displacement blower, it probably can make an increase in velocity since it is pumping air.
It helps until you reach 100% V.E. after that to cram more air in you have to pressurize the air which only increases its density not velocity.
Richard Holdner has shown the power curve under boost mimics the power curve NA as long as the boost and drive pressure ratios are close to 1-1.
I know I'm getting to far into the weeds here but, boost should help pressure wave tuning (that's not velocity though I guess).
COANDA ?
Here’s my argument based on my dyno data on late model fuel injected Harley’s using throttle by wire. port velocity on such a short intake runner length using electronic throttle is no longer a concern as the throttle blade or velocity valve as I like to call it can be mapped to maintain peak air speeds at all accelerator positions or torque requests. As for the 170 port vs 195 port , for that specific cam timing the 170 was better, but change the cam timing to take better advantage of the 195 and my bet is you will make even more power correct ? the more we increase flow the less time we need to hold the valves open so the piston does more work .
Place an electric diagonal fan on top of a piston in an operating cylinder. When the piston is at BDC on the intake stroke, the diagonal fan will generate a lower pressure area on top of the piston attracting air to flow into the cylinder through the intake valve even though the piston is rounding BDC and moving toward TDC. The spinning fan will obviously encourage air to flow into the cylinder until the intake valve closes. Remove the diagonal fan and replace it with high velocity swirl energy generated by a purposely designed intake port and it will act exactly like the diagonal fan and allow air to enter the cylinder by increasing the velocity and lowering the air pressure even though the piston is moving toward TDC until the intake valve closes. As opposed to a lazy/large flow/low velocity port with no swirl energy that allows the air pressure in the cylinder to equalize with manifold pressure at BDC and the rising piston will simply push all of the air previously captured, back into the intake port before the intake valve is closed. No ram effect, no volumetric efficiency, no power. ☺
If only Ford "Sewer Pipes R Us" Motor Co had known this when they designed the 427 Tunnel Port, Boss 302, Boss 429, 351C 4V, etc...
🎯💯. But keep in mind those ports work at 9000 RPM! 😂😂😂
Depends on cubic inches and usage of engine.
I've read your SBC book enough times over several years I needed to duct tape the cover. All while buying many recommended parts and brands along with your spec cam from Lunati, I'm very pleased, did the go, now time for the show.
But DV, you have to do something about these full length ads and not being able to skip after 5-15 seconds, please!!!
There is no dought that head desingners have used your knowledge to then call there head the Best!
I haven’t watched the video yet but here is my thinking. For torque go with velocity (pack the cylinder early). For max HP go with FLOW. The more air = more fuel = more HP.
So, now I’ll watch and see if I’m right.
I need a porting school
Displacement and rpm range dictate the choices in port design
No velocity nothing moves
Very Good Video DV
The holy grail is here, one only needs to be still and listen
Thanks, DV. v/r wh
Thanks DV
Thanks!