Eric 20 years ago when I was racing hydro plane boats we dimpled the bottom of the boat where the water would hit on the last12/15 inches of the boat bottom. The boat was faster by a few MPH. No one could see what we had done. Then we dimpled the top but only for testing. Again the boat was faster. ( we put the same motor on 2 different boats) It worked every time we tried it. We never did run it on the top racing but ended up doing the whole bottom that you could not see standing next to it. After we got out front we just put distance on every lap. You will find the better you can keep the pattern the better your results. Kind of like a golf ball it allows little vortex so the air can not stick to the surface. Rick
Richard... there was a similar technology used on America's Cup Yatchs in the paint finish like fish scales that got you about another 1/2 knot in boat speed, altogether are different kettle of fish because we are taking boundry layer friction not mixture distribution.Trev New Zealand 🙃🇳🇿
I heard dimpling boat hulls actually creates more friction. With air you get a boundary layer from the turbulence but i think it doesnt happen on water... not sure.
@@blivetsoftruth we only dimpled the botton of the boat that was touching the water when on plane. For our hydro's12'/14' it was about the last 12"/14"
Love the series, Eric. I’m 22 now and have been obsessed with cylinder heads and flow numbers since I was 15. My friends were out playing football and partying while I was trying to build engines and go fast. So glad I came across your channel
Pick up a head off an older honda accord ex, f22b1 engine code. They are rumored to flow just as well as the hand ported b18c Type R heads from Japan. I'd be interested to see if this is true.
Build yourself a small Flowbench like I did in my teens....actually I was thinking about marketing that kit for small head porter's etc Thanks Trev New Zealand😊🇳🇿
I've been watching a ton of these. Have a theory about why partially dimpled works better, and where you should partially dimple. A golf ball is fully dimpled only because it needs to be round and it spins. Dimples everywhere don't actually help in a port because its a closed space. Here's the theory: The dimples actually do two things: 1.) Decrease the available space for air to travel in the port by creating turbulence near the wall. But the air flows over the turbulence with lower friction that it would normally and, as a result, flows with higher port velocity. This is always the trade off you are making when porting: volume vs. velocity. 2.) Reduces pressure on the boundary between the turbulence and the flow. This is why the air bends around a golf ball, reducing the size of the low pressure air bubble the golf ball has to drag behind it. So wherever you'd like more flow and less volume, add dimples. Whenever you want to increase the venture effect (around the neck or around a bend) add dimples. Here's how I used this information: (Porting Buick 350 Heads...very tall narrow ports which is kind of ideal.) 1.) Drew on the inside of the intake port with a sharpie a rectangle. (Where atomizing fuel occurs.) 2.) Drew on any surface where the port was becoming constrained on the SIDE OF THE CONSTRAINT a rectangle about 3/4 of an inch before and 3/4 of an inch after. (If the port bends left, this will be the bump on the left side...or the inside). 3.) Drew a circle on any part of the port where I want the air to bend in that direction. i.e. on the valve guide slope. 4.) Drew a circle on the biggest side of the bowl. (Bowls are all about increasing the venturi effect over the valve seat.) 5.) If I did port matching (Don't make the mistake of doing it to the gasket. Match it up with prussion blue with no gasket.) I added dimples where material was removed, bending the flow in the direction of smooth wall. Then using a round diamond bit on my Dremel I added dimples where the circles or squares were drawn in sharpie. I smoothed everything else. I don't have a great flow bench setup, but do have a meter and a shop vac. I had significantly increased flow 15-20% on the first two ports I did at lifts from .200 to .450 roughly. Need to test on a better bench with better flow tools. From a HP/Torque perspective this is ideal as the valve spends the vast majority of the time in these positions. I'm actually working on the perfect project for this: Buick heads are notoriously difficult to get gains from porting on beyond simply making them smooth and making the neck 90% of the valve seat. I'm completely against full dimpling unless you want a smaller port. (Which if you watch David Vizzard's videos it actually might be a good way to make the start of the port smaller without having to fill it!) I'd have to check that on a head that needed it, and the Buick 350 heads don't. I also dimpled on one side of my combustion port! The part between the wall and the valve seat....so the smallest area. So many videos say not to polish this part, that I HIGHLY suspect it needs low pressure on this side to maximize the velocity and as such the venturi effect. My guess here is that air flow in this spot is ALWAYS turbulent with crappy flow, so bending the air over the lip into the cylinder wall is well worth the sacrifice in volume. I hope I don't end up with early detonation, but I'm only running 10:1 compression and the cast iron should run cool enough...I hope!
I remember the first time I saw an intake manifold that had "selective surface finishing " done to certain areas. Instantly made sense to me what they were trying to accomplish.... I decided to give it a try on the next intake I ported and the time it took learned me on why everyone else didn't do it... lol. Time consuming...didn't make much if any proft on that job but the customer was blown away and it ran excellent.... when I sat down and figured up the $$$$$ to make this profitable, I knew it was going to be very few that would pay for that level of work on most jobs.... that said 25yrs later I still do it to my max effort stuff.
@@muthatrucker6485 the cnc is not free to run, it consumes power, tools, and maintenance and of course it doesn't have a different paying job in it so the opportunity cost is significant.
@@muthatrucker6485 A decent CNC machine that will do this costs around $40k and beyond. That does not include the multi-stage/multi-phase power delivery that is required to run it, the cost of the tools, the maintenance.... and the time required to actually learn how to draw in CAD and do the actual R&D required to find the best pattern to actually increase velocity and provide turbulence to keep the atomized fuel from pooling. Its not easy to setup. Time is money. As far as I know, there are literally only a handful of machine shops around the world that even offer this process to ANY cylinder head. And doing it by hand, is not the way to do it because you need to do it in a specific pattern, with specific tools running at specific depths. Its why you can ONLY do this on a CNC and actually be able to show increased airflow on a flow bench at any variation vs doing it by hand and not actually knowing what you're doing like this video shows. The only way to get an actual repeatable results from dimpling, across and entire range of airflow, is through a CNC machine. And like the dude said, very few people would pay for such work as in the grand scheme of things.... its almost never worth the effort.
The dimple intake was something used by Germany's Veicomer Performance a few years back. They had CNCed all the heads and had hard data. It was to limit "Laminar Flow." As I recall, the problem was, the length of the intake isn't long enough for the dimples to make that much difference. It is cool to follow each engine builder's experiment. This is what it takes to find horsepower. Cool video!
its beneficial on two strokes, but even then its only minimal in comapriosn to moving ports, power valves, responsive reed valves and a properly resonant exhaust, one might think that in an airbox design? it might actuall be of a bit of extra benefit,
@@mitchrichard8551 you want to prevent laminar flow, at the boundary. It's a fine line though and is really complicated because laminar flow at boundaries stabilize the flow and can prevent it from separating and becoming turbulent. But with proper engineering, turbulence at the boundary will provide less resistance than laminar flow. Think about why there is always less wind at the surface of the planet than, say, a couple hundred feet up. Air literally sticking to shit down here fam, and it's (at scale) pretty laminar.
I did this 20 years ago to a set of heads. It gave much better throttle response and didnt seem to hurt top end power. It was alot of work and my hand hurt afterwards for a week.
The reason dimpling works on a golf ball is that air actually sticks to the ball better and increases the pressure of the air behind the ball. It's not much but enough. This increase in pressure effectively reduces the drag of the ball. The port isn't moving through the air. The air is moving through the port. There's no low pressure area behind the object being dimpled to slightly increase the pressure of to allow for reduced drag through an airstream. Dimples work on objects with a low pressure region behind them as they travel through the air. Not stationary objects with air flowing through them. Whoever initially tried this made a wrong assumption about what was happening to a golf ball and why the dimples worked. But at least they were trying.
They discovered that shark skin has the ability to form thousands of dimples all over the surface sorta like a golf ball to reduce drag and help them swim faster. Then the Speedo company started making swim suits to mimic shark skin. Then in 2008 they were worn by almost all athletes including Michael Phelps and tested in the on the world stage that year and broke 13 records. Subsequently the shark skin raceware got banned from the Olympics.
To my shock, I saw a Pro Stock manifold from 15 or so years ago, with hundreds and hundreds of ball-end milled dimples. They must have done this work before it was welded because some areas were impossible to get into. Between the epoxy and the machining, this manifold was amazing. I have no idea how well it worked, but it was a work of art!
This is exactly what I was here to say. It would have been worth it if he had done the test before and after and normalized the test per the differences in each cylinder to separate the testing differences.
"Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball's surface. This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake. Scientific American
That is interesting concept. Have to give you the credit because that's how you find out things and you never know until it's proven wrong. Fluid dynamics is very interesting. What about little runners of blades along the walls. I would not know how to install them, but it would be worth trying something different. Good luck with your testing. You should retest 3 to 5 times then average you numbers unless you can really rely on your number for a bass line and result, so you know it's not a fluke.
I think the dimpled principle is worth exploring but a golf ball moving 400 feet per second is different from air moving through a cylinder head under vacuum and with the valve pulses. So they might have to modify the size of the dimples or invert them. But I definitely think it's worth exploring.
@@scottshields8334 I have tested your hypothesis to see if it could be disproved using the scientific method. For the test I simply obtained a golf ball and an engine head. As a control I obtained a second golf ball and an engine head and set them aside under 24 hour surveillance to ensure neither of them was sexually attracted to the other and engaged the other in intimate relations resulting in reproduction of like kind. I then observed the first golf ball and engine head and compared them geometrically for consistency of design. Neither of the objects observed displayed any discernible similarities in either shape, size, colour, weight, mass, intended use, common use, form, function, retail price, or resale value. I'm sure Bugatti would agree.
I was told the other effects of turbulence in the head ports are the better fuel atomization for a better mixture thus explosion. But the flow rate changes are very interesting and great theory. Great job.
I always assumed it wasn't a flow increase but a swirl type action to increase the mixing of air and fuel for increased combustion hence why exhaust stays super smooth
The reason that partial dimpling increased flow is that moving fluid always tries to follow the path of least inertia. The Coanda effect will no allow it to do this, forcing it to follow the contour of the port and slowing it down. The dumpling on the port floor and the back of the bowl create turbulent areas that effectively raise the laminar flow off the bottom of the port and straighten it away from the back of the bowl without fluid-to-surface friction. Think of it as a way of angle-cutting the heads and raising the ports, without angle-cutting the heads and raising the ports. Dimpling the whole combustion chamber, on the other hand, creates turbulence that washes away lean spots and allows you to run higher compression and leaner mixtures for a faster burn without knock and more power up top, making it ideal for open chamber heads that breathe well, but need a lot of timing advance.
I dimpled the intake ports on a methanol burning Briggs & Stratton go kart and it made quite a difference in power. I also found that if a I keep the head temp between 375 and 400 degs it had better response. If I let the head temp get over 400 deg. the piston got too big for the bore and would break the block.
On the dyno it gained nothing. I still have a wka , dyno cammed engine we dynoed that was dimpled. It lost everywhere in the rpm range. Don’t waste your time.
I have done this for decades on FE heads, identically and back into the intake manifold and the same distance from the SSR and the back of the throat. The partial dimple job is the best short of welding the floor. I also angle milled mine to 12 degrees but faced to 13 for the best manifold interface. It is a good alternative on iron heads to welding. Aluminum, I would weld to shape. It is quite surprising that the early 61-65 iron FE head is to the LS. Ford engineering was pretty good for their time. But the dimples when placed as the partial job is can pick up an iron head nicely with only the cost of your labor if you DIY it.
Cool only partial dimpling, where air needs help? Only the floor of port? Sharp raduis? And the area just before the valve head(also dimpled)?What tool should one use round de-bur-bit what size? And patern?. (GrassRoot racer 4cyl 8v methanol looking for a legal edge)
After watching your video several times, I did some digging/research on the aerodynamics of dimpling. Most of the information I read was over my head but I was able to cyfer a few things from the scientific research from the smart guys..... #1- dimple size ratio to the area. #2- dimple depth #3- dimple edges (Sharp vs smooth) #4- the angle at which the airstream approaches the dimples. #5- the correlation/placement of the dimples to each other. ☆All in all, if each one of the conditions listed above is just right, then the velocity of the airstream is increased by the reduction of drag. Like I said earlier, most of what I read was over my head....lol I'm not sure the human hand and eye can master such percission. But I'm gonna give it a shot....😂
We would use a tiny carbide ball shaped burr and flatten two sides. The burr was played across the surface, providing a uniform stippling effect. Small stipples induce a smaller boundary layer for the laminar mass flow to traverse. Typically larger wall deviations will increase the stand-off height of the dead air layer adjacent to the wall. Stippling does reduce structural dynamic drag on mass flow.
I think you are exactly right! I even though about using different sizes to help shape the port funnel to more idea sizes. I think there is a place for bigger dimples: specifically where you want to trade volume for velocity.
The belief is it makes the port act “smaller” by creating a barrier for the air against the wall. My machine can do that but I’ve never tried. It can cause fuel to puddle in the dimples at low engine speeds.
You can believe all you want, it simply wont improve anything and all it will do is make you pay at least double the amount of money a proper cylinder head job would be but if you really want it you can go ahead and pay for it.
The vortices created by the dimples work in some areas and not in other because they help maintain laminar flow and reduce overall turbulence and drag caused by air separating from the surface around tight curves that are away from the direction of travel. Curves that are towards the direction of travel need to be as smooth as possible or they add friction. Only the bottom of the port needs the treatment. The rule is if it hits it needs to be smooth if it follows dimple it. You could also try a series of fine grooves across the floor of the port. The dimples or grooves only need be near the valve opening just before the curve not the entire floor.
Wow! Partial dimpling was the most effective! I never would have guessed that full dimpling would have detracted from flow. Cool test. Looking forward to the next testing.
The reason a dimpled golf ball flies further is that dimples cause the flow to remain attached longer as air flows from front to back. This reduces base drag. It only makes sense in an engine to add it to the short side radius, helping air to make the turn into the cylinder
I agree with Eric not dimpling the SSR, air speed already increases in that area and if it nears 380-400fps the fuel will separate from the air, hitting the back of the bowl and entering the chamber as raw fuel droplets. I am curious if Eric thinks the eddys on the back of the bowl would help reatomize any fuel that has fallen out of suspension.
I too thought it was very smart of you to dimple only the low flow areas and measure the results before moving on. What remains to be seen, however, is what the ideal configuration is for the dimpling. How shallow/deep should they be? What should their diameter be? How far apart should they be from each other, on any given row? How far apart should the rows be? There's a wide range of possibilities, obviously, but it shouldn't take a great deal more experimentation just to get headed in the right direction. Once you find something that yields even better results, then it becomes about tweaking THAT configuration a bit to see if even better gains are to be had. I like this a lot. I would definitely try to find a better way to get the job done though. Take a mold of the areas you plan to dimple. Then use that mold to form a thin plate. Carefully mark up that plate with dots, and then use a drill punch on those dots. Now you can drill a uniform set of small holes. Temporarily glue that plate onto the face of your port and let those holes now serve as individual guides for your dimpling. Since all things at this stage are equal, you control depth simply by clocking time. I take it you're using a dremel with a small ball grinder. For each dimple, bring it up to speed and then with uniform pressure press it into a hole for, say, 10 seconds. Who knows, maybe 11. You get the point. Find the right amount of time and then follow the exact same process for each dimple. It is possible to obtain perfect results even by hand if you use the right approach. Also, since you still have the molds from which the first set of plates were made, you can experiment with all remaining ports to determine hole placement and depth. Just make a whole bunch of plates and mark them up differently.
I should have read your post before posting mine. There are many variables and I'm not sure the human hand and eye can master such a feat. But you never know until you try.😂
The huge intake tract surface finish thread on Speedtalk goes into a bunch of theoretical territory. The most interesting hypothesis is that dimpling creates a series of vortices in the boundary layer which assists in keeping fuel in suspension. That should be dyno tested as almost no one in the industry has something like Siemens Star-CCM to do a multi-phase CFD analysis.
To explain it simpler, air travels faster over air, the dimples create pockets as he said for the air to ride creating a boundary layer and the air in "free stream" then moves faster
The turbulent boundary layer is made thicker by dimpling which causes turbulent eddies that act as ball bearings for the flow. I don't know what it works best for... high/low pressure or high/low velocity
An old hot rodder I knew back in the 90’s dimpled the top of the piston, in pretty much the same way. He said that it made the combustion chamber less sensitive to detonation & that he was able to run the engine with higher compression ratios.
@@ragimundvonwallat8961: you’re probably right, but it would be nice to see some real science directed to the question to see what effect it has, if any.
@@loganshotrod4x464 it you make dimple by taking out material out of the piston the only anti detonation effect you'll get is by the fact that you lowered the compression... but even with that you must take into account that you created alot of ridges...and irregular ridges at that those create hot spot that increase detonation, as a last malus now you have a set of pistons that are all different weigth so you have to rebalance all of that. as i told you, hogwash, never do this
Those dimples cause a circulation and the air/fuel that travels over the dimples circulating dimples air speed up the air flowing over it. Same effect as a truck bed. The biggest issue I see when people flow heads on the intake side is they dry flow the intake ports yes if it's direct injection then yes dry flow it but if the fuel injector is in the intake manifolds then you need to wet flow the intakes. People argue with me all the time about this subject and as soon as I ask if they flowed it wet I don't get a response.
Eric, I've wondered about this dimpling for a while and appreciate the info you have given us. I'm building a 408" SBM ATM And from seeing this, I'm going to apply this dimpling to the heads. SBM are already a 18° head stock but the port floors always need raised to really take advantage of this and dimpling may help this in a huge way. I'm using new magnum castings and going to 2.02/1.62 valve package along with opening the CSA of the pushrod pinch which is a huge choke point on these heads, I'll use bronze filler rod and braze up the outside of the pushrod pinch .050 so I am able to increase my CSA to where it needs to be. Also since your doing this, would you be interested in doing a magnum head? We would donate a casting and ship it to you for experimental purposes. I understand it's iron head but your lacking any Mopar head stuff on your page and I believe it would help grow your page. Let me know and I can send you my contact info, thanks!!!
The best demonstration of this effect and why dimpling can help is what happened when they built the Hoover dam. They first built smooth spillways-tunnels and the water ripped the floor apart from cavitation. We mostly know it as "washboard" on the roads. They remade the spillways with grooves cut in the floor 90 degrees from the flow of water- problem solved. The little vortecies created from dimpling in high pressure areas act as little ball bearings for the air to flow smoothly across. But it has the opposite effect- creating drag in low pressure areas.
I think there's several reasons why this could be helping. Which ever way you think about it, you're getting higher pressure leading up to the short side radius, driving a larger pressure differential into the cylinder and faster air flow.
I'd like to see stepped slots in the same place as the partial dimple. With the same size and depth burr. Like a set of stairs leading to the bowl. Leading to step slotted rear portion of bowl.
Recommendation is to just dimple the change of vector of flow ... around the opening and the change in direction at curvature before the valve opening. I wouldn't dimple the first 2/3rds entering the port, just the area immediately before the valve opening. If you can place a dime on a surface and it rocks more than 10 degrees, dimple under the dime, if not don't. What you want to achieve is a reduction of flow that is fighting the path of flow. Think of it as reducing parasitic loss. Those eddy currents fill the areas that are redirecting flow back against the incoming flow. So your first partial dimpling was a bit too aggressive at the port entrance. I bet you get even better numbers if you do a partial of your partial if you get my drift. And then polish where you didn't dimple :o).
Cool, you recon you can ruin the (dimpling)effect by doing the whole surface area of the intake port? Is it for carburetors effective only?Or would old school 2 valves per cylinder heads in fuel injection form also benefit also benefit from dimpling?
@@nicopotgieter453 It's for ports with high angles to the valves. Yeah it should only be done where the angles change rapidly. Polish the rest. Don't think ya would 'ruin it' with it totally covered. Port injection usually adds a significant directing flow. On everything else even direct injection yes. Well maybe not on boost over 4psi. It's mostly throttle response you make gains ... not so much in power. We talking about old 300+ v-8 displacements too. Inlines don't have the issue as much with valve angles. Although i did work on a honda magna v4 back in the 90.s.
@@ejrupp9555 Thanks for the reply, appreciate more than I can express. Fascinating really, cuase no engine the same with differnet setup it seems some stuff work better than other and in some cases nothing at all. Honda WSBK SP2 VTR 1000cc V-twin superbike had dimples on the lips of the trumpets in the early 2000's. At it was Honda Factory HRC team. The injector was on the outside facing the trumpet(bellmouth) though. Like in early N/A F1 engines.
@@nicopotgieter453 So it was in the area with the fastest exterior angle change ... yeah that makes sense. Because in flat areas or negative angle changes (Less than 180 degrees) it is not useful. as the video results suggest.
We used to do this (grooving or dimpling) only on intake manifolds to create turbulence. It is only effective on carbureted and mono port injection as the turbulence helps to keep the fuel charge in suspension (Mixed with the air). We often ran a slightly curved or spiraled grooving to create some cylinder swirl for scavenging. Porting and flowing can offer significant gains depending upon the engine design or intended use :)
@@nicopotgieter453 Fuel injection (Port) has a pretty good atomization and fuel/air suspension rate to begin with, so some of that was aimed at promoting cylinder swirl. So for carburated and mono port injection (sometimes called throttle body injection) the intake turbulence assisted in keep the fuel suspended (atomized) in the air. The swirl direction inside of the manifold has to follow the natural valve and cylinder swirl of each cylinder of the engine. It's difficult to get good (uniform) dimpling inside of a manifold tube without splitting and re-welding. In all of our tests we gained a small amount of power and fuel economy, but these gains are not large. You have to think of it the larger picture of performance tuning and all of the other "small" gains you can pick up. > A lot of people had a concept of "Bolt on" power at the time, adding this or that to get better performance. I ran with the Phil Irving concept of "removing" what was holding the engine back, often friction, weight, poor tuning (or "Good enough") factory engineering. Most modern vehicle engines are modeled to some extent off of Phil Irvings race engineering. Phil Irving: Rich Mixture, Black Smoke and especially Tuning for Speed.
@@nicopotgieter453 P.S. At the time we had some heavy transport department restrictions on hot engines, so hiding the performance tweaks was part of the game for street cars :) Personally I have nothing against dropping a supercharger onto the side of an engine if it's internals are strong enough to handle 4 to 8 psi boost and the laws allow for it :P Legally in Australia we can only get away with MAX 4psi boost on certain engines.
@@axle.australian.patriot Thanks for the reply. So fuel delivery near perfect in fuel injection to be of benefit(dimple). Dimpling a band-aid(Carburetor)to get closer to fuel injection. effeciancy. Unless you had an early fuel injected 90's car maybe? Reason Im asking from beginning. Grassroots racer with early Golf 1 1600cc 8v (U-Flow) methanol. Trying to look for hidden horspower. Even if is.1-2%.Is fuel injection though but not the most powerful even compared to other competition 8v fuel injection from same era stock or modified(more powerful than Golf 8v U-Flow). The Golf U-Flow alwas a smidgen behind in HP game(in my 8v 1600cc 4cyl racing class)
Somewhere around 20+ years ago, I read an article in a magazine dedicated to sprint cars about a shop that built sprint car engines doing dimpling. Their reasoning was that dimples on a golf ball make it fly farther. Maybe it works externally but doesn't increase air speed inside a tube (runners are basically tubes). They didn't go any flow rate numbers, before and after so no proof of increased flow was proven.
Like the theory then testing to prove what works. Answered several questions I thought of and you tested several of them on the flow bench with results.
We always left the intake surfaces a little rough not just for flow, but because we were using a wet nitrous kit the rougher "hatched" finish kept the fuel from pooling up in the port.
Thank you for testing this. What about ruffles instead of dimples? Water and air react similarly. I used to make Berkeley jet boat castings. They used the Bernoulli principle to greatly increase water intake volume. You can test it by dangling a spoon under a slow running water faucet and see how forces the water into where the intake would be after the spoon.
Raise the floor of the port. You can fill it in with epoxy. Increase the radius of the short turn and raise the roof of the port to to match the floor. Maintain the bias of the intake runner but you can make it wider if there’s enough material to do so. The guys on Mythbusters dimpled an entire car and it reduced aerodymic drag. Dimpling should help. Now to watch the video!
@@PantherSerpahin same, I remember back decades ago there were intake gaskets with screens in them to help keep fuel atomized. No idea how well it worked with the trade off of better atomization, at least in theory, to the reduction in theoretical port size.
I’m used to fooling around with old iron heads. All I’ve ever known to do was clean up the rough castings and gasket match the intake to the head. Very interesting gig you got going on here.
U know way more then I could ever know about this stuff. So ill take your word for it and seeing the data helps too. I just built a decked out stroker big bore and ported out 4 stroke atv. And I thought about doing the dimples on some of the intake but decided against for lack of data out there. Deff much appreciated man
That is exactly what I have seen. I only dimpled the weak spots on an iron head. It improved just as if you were able to fill it with weld. The dimples on the FE head worked really well, but it is in selecting the area by listening to the flow bench.
I know Smokey did it in the 60’s with a blunt center punch until Nazicar outlawed it. He also dimpled the dome but he did smooth them out to prevent hot spots and predetonation.
HA! Nazicar...funny, you just made my day. Thank You. There were quite a few innovators in stock car racing. Just couldn't get by the people who didn't know much about racing, just how put on a show they thought the fans wanted to see.
Get someone on here who does cfd. The dimples would be more effective if they protruded into the boundary layer. Since its turbulent flow and not laminar protrusions into the boundary layer will have more of an effect than dimples.
Im so glad i watched this video! I have started an experiment with a RTC-15 Predator 212 head. With such a short port to begin with i thought and thought on how dimpling could affect flow. I did as you did, starting at the opening of the shortside floor being more aggressive. As i went towards the bowl, i put more distance between rows , AND reduced the size of the dimples. I just had a hunch this would be the ticket. I havent dimpled any of the bowl area (as of yet) Questions: 1. Should i hit the backside of the bowl? 2. Should i dimple any of the intake tube? Keep in mind this head already has a pretty aggressive bias swirlport and it really puts a good swirl affect on the air. Ive put smoke through several of my heads, AND with just my standard bias swirlport see unconventional gains in power. Its amazing the power gains im seeing all across the board! Especially mid to upper rpm range! Thanks!!!
BOY, do i enjoy your tech......i thought ur intial idea on the dimples was rite on, i thought FULL dimples would ruin the venturie effect, and i was right, and so were you!!...i look fwd to ur next vid on the valve job.....i have learned ALOT from ur vids......i'm the bracket racer class advocate guy from the other day....GREAT STUFF!!......btw, i'm at 10:90's now on pump gas, 462 cid Pontiac, Kauffman Racing heads.....lookin fwd to ur next vid!! TY for ur sharing of ur expertise, and if you told us all ur secrets, you wudnt have YOUR race cars, so, keep certain shit to URSELF FOR SURE!!
@@notme810 HA!...i may try, but I wanna get the best program first outa Kauffman.....i have the 310 cfm program now, they offer a 340 cfm program on my heads, i think they have a 360 cfm as well (i have their D-port, with a modern chamber) i went from 36° total to 31° cuz the chamber is so efficient.......i'd love to do that first, then talk with Jeff (Kauffman) on the dimples......he's a great dude, down to earth, and ALWAYS responds to my e-mails......TY sir, for the input....i can see how my 4.210 stroke cud benefit from the tiny eddy's.....creating even more velocity, to help my V/E Get up there around 100% if not more!!....TY again!!, seems subscribing to the channel, has already reaped nice benefits, from folks like you!!.....btw, i've built a # of FE's at my shop, they sure are some BRUTES, i tell ya!!.......
thank you so much mate for making this vid ive allways wondered this seeing how mythbusters did the dimple car can wait to see how it go's mate thanks you
My explanation would be that the dimples slows the air down on the inside. It helps to stream the air trough the corner. (You trip the air the right way)
Exactly. Only a well researched and tested CAD file, using extensive fluid simulation - is the absolute ONLY way to get a dimpled manifold to work. Doing it by hand NEVER yields the same results that actual machine shops that offer this work that have been doing it for 20 years. If you look at the Veicomer videos, their dimpling method is the same across every single cylinder head and there arent as many dimples and are much larger and smoother. This guy just used a dremel with the cheapest bit - no wonder he didn't see any increase
what we did was take a set of 202 angle plug heads ported all ports water, oil drop, valves to 204 and ported the intake and exhaust plus had to port the intake to match the heads . we wanted cast on cast on a pro built 327 for high rpm engine for pump gas only . old man bell built it i just helped learned a lot from him . i have had the engine to 15,000 rpms many times has lasted over 20 years of street racing ,cruising and just driving it hard. was the fastest in my area on the street back in the 90's for about 3 years with pump gas only . it pushed over 1200 hp just pump gas 13.5 to 1 compression with a tunnel ram started with rick news dragster engine and built the shit out of it . even seasoned the block polished it over size cylinder walls what bell calls supper stroke it . he called it a indy block with a dragster top end
You should see the biggest flow increase by dimpling the short radius only. Well, maybe just the short (or bottom of the port). So basically the partial porting you did, MINUS the dimpling of the bowl PLUS dimpling of the short radius. Golf balls are dimpled to make them travel as far as possible through the air. If the surface of the ball was smooth, the airflow around it would detach early creating drag on the back side. This drag would effectively pull on the ball in the opposite direction to its flight path. The dimples disallow this early flow detachment greatly reducing said drag. In other words, no dimples, the airflow detaches somewhere shortly after the equator of the ball. With dimples, the airflow remains attached to the spheres surface well into the back side. Thus, the air is better able to follow the balls curvature in full. For cylinder heads, this means more airflow as the air pressure past the valve on the short radius side is often lower than the opposite side. So better airflow, and potentially even better fuel atomization than more cfm alone would generate. Oh, and the dimpling of the top side of the port basically causes more resistance to the airflow since the air is colliding with a concave surface that is not smooth. So dimpling on convex surfaces...yes. Dimpling on concave surfaces, maybe not. Flat surfaces are somewhat indifferent I feel. How do I know this...? I studied the mathematics of fluid mechanics in graduate school :-D
Dimpling gives only 1-2% better flow. More power is hidden in size and shape of port and valve job. But if you are looking for that last 0.1% of power gain it's a good mod.
Really appreciate the time you spend on these videos. Apparently many others do, too, as you are growing a healthy subscriber audience. Congrats on that.
It would interesting to create dimples in the floor by impacting with a hammer and punch. This might create a small ridge around the dimple. Helping to raise the floor a bit.
Interesting but myself I polished my intake & exhaust ports I had the exhaust ports as smooth as glass the intake ports were final sanded with a 120 grit sandpaper then I sandblasted the intake ports washed out the ports to remove the sand grit then compressed air to dry and blow the clean and it worked very well it keeps the air / fuel mixed all the way through the port . . sometimes old school is the best and won't destroy an expensive set of heads
I have had great results with a Newen seat cuts on the valve job. Average increase has been around 12 cfm on intake. It incorporates the pressure recovery into the cut without a second setup which reduces error.
It would be interesting to see a stock sand cast iron head done with the short side/s left as cast, other than any obvious ridges, and the rest just smoothed out without trying to go crazy on the modification.
You should try WPC treatment on the inside of the port! They say it reduces friction significantly but maybe they just mean between two metal parts… idk but would make a fun video! Love the content! Keep it up!
WPC only benefits parts where there is friction between two parts, such as a rod and crankshaft, or the wristpin and piston. WPC treating a cylinder head has zero benefit and a waste of money. Anti-friction methods do nothing for airflow
No at best a few grams of material loss is going to have more effect. With direct injection I would say 0 effect at all with port injection just pits to collect garbage in imho. No extra air is going in mix will likely be worse as the pits would serve to collect fluid l.
My question is how does the liquid-Fuel react to the dimpliing and would I see the difference on the dyno of the best results of partial dimples. Thanks
So what I believe is that as air goes thru the ports that are dimpled we get more turbulent airflow , so when the atomized fuel is injected in the port and goes into the cylinder to be combusted the air fuel mixture has been mixed much more efficiently that other methods, theoretically it should work like that lol
Do you mean atomized fuel,as in carb/MPFI application? Large drops of unatomized liquid is bad juju. If the demples improved Volumetric Efficiency, then it increases power output or lean out your current setup.
Only dimple on the lead-in to a short side with divergence greater than 6°. If it's parallel, converging, or diverging lass than 6 then leave it smooth.
So where is the best place to put the dimples and where should we stay away from. Salt Flat Runners sometimes do the same thing but they leave certain spaces polished🤔
Full dimple reduces port size via boundry layer think golf ball provides lift and reduces resistance around ball but increases surface area shrinking port size due to enlarged boundry layer. The partial behind valve and on floor good and you proved it as little flow takes place there and more boundry layer in those areas improve flow into valve pocket and combustion chamber.
Exhaust valve: on the face of the valve, the part you see in the chamber. Round the edge of it so the air can navigate around it and get into the port easier. I chuck it up in a drill and do it by hand on my bench grinder and then my belt sander. It’s usually good for about 5cfm almost everywhere.
different, would it make sense to have a dimpling setup plate made on a waterjet, or lazer cut from say 16ga steel that could be formed to the bottom of the port to do a partial dimpling, and have more consistant dimples? at least it would be a parameter of this to try.... you could also trim the dimpling plate to fit your application/port and specify a size ball burr to be consistant... I imagine the eddy being created in the port hinders/restricts flow/volume especially at higher rates. I find the idea of port design interesting, and am enjoying seeing other designs & ideas implemented.
I run a small CNC shop with 5 axis machines, I've always been very interested in engine building but never had the time to get into it, this is something I've been wondering about for a while. As someone with lots of 5 axis machining experience this would actually be super easy to do with the right machine and software. Side note I'm always shocked at how poor the surface finish is on CNC ported heads in aluminum it should be easy to make them looking like mirrors, I always wondered what a mirror finish with dimples would do.
@@85CEKR The boundary layer is an area next to a surface where the flow does not separate from the surface but clings and drags across. Dimples would typically fix that, but the rough surface finish on most cast heads is enough because for the dimples to be effective, the air pressure needs to be higher and the velocity needs to be lower than conditions in an intake runner.
10 months late and maybe it’s mentioned in here but the dimpling should make for “slipperier” port. The air “sticks” to the surface due to friction like any other solid or fluid. I remember a segment on Top Gear when they highlighted the air channeling on the Ferrari F12 how it’s send down the sides of the car which creates a boundary layer of air for air flowing around the car to slide against and therefore less drag. Same idea, bigger boundary layer, more air “lubrication”…more flow. With the partial dimple you had more flow which more or less proves this. The full dimple shows less flow and if I followed correctly the “full” had the dimpling down by the valve. The decrease is probably due to some reversion which is due to the added boundary layer and turbulence in that area. Idk just my 2¢ taken from what I learned in Fluid Mechanics in college
We always used a special tool that put a very coarse surface around the port or perpendicular to the airflow. Like very coarse cone Not talking about sand paper now. The surface ends up feeling like sandpaper you cannot use sandpaper to produce it. You would have to put a million dimples in that port to make the same effect. Like peeing the surface. It must be "regular" and minimal in relation to it's size like 1 to 100. If diameter is 2 the roughness should be . 002 in proportion but must be regular. Reality is it's the change of direction where you must have the detail. We always treat the entire surface. For sail boats they make special plastic dimples that come on the sheet makes it much easier to apply. The only place you will see a detail on a relatively long flat surface is on the departing side meaning two surfaces at a slight angle to each other just beyond the point of the divergence surface roughness causes the fluid to remain in contact with that surface, 5 degrees of changes is already enough. Oh by the way air is fluid, air with anything entrained in it has more density and inertia.
The boundry layer is almost always going to be around .100" thick no matter the surface, it's simply near dead air, the closer to the surface, the slower the air moves...
The premise is to loft the mixture over relatively dead areas of the intake tract, I have done it to plenum floors also. The Ford FE is a great garden variety head with CJ valves and even 2.19 5/16 stem intakes to get over 600 hp with. Aluminum welding is better, and less labor intensive. But if a certain casting is required and this modification is allowed or you just want to mess with people. Lol, why not?
Love the video just a little confused at 5:00 you say you would’ve filled these areas up with epoxy on the partial dimple, but why if the partial dimple yielded the best results
Much obliged Sir for the insight, I'm interested in the partial dimpled port specially the port entry lower floor, any insight on the affects on airspeed, Did the lower floor airspeed increase? Did the air speed variation from the upper wall to the floor became more uniform, emphasizing the area from the port entry till .5 inches before the short turn?
Very interesting investigation video, you're quite right about the effect on boundary layer and that it would increase the air velocity by narrowing the effective passage.... But I don't see that it would increase total airflow.... Isn't the whole point of port polishing to maximise laminar flow, i.e. the opposite of dimpling? Then again I would expect dimpling around/after the injectors to help with atomization. I'm no aero engineer, but I guess to get this right you'd really need to do some modelling in solidworks..
that old english guy david vizard has the numbers. he has 60 years of head work, from F1 to Nascar. He does mention the golf ball dimpling of ports but never reccomends pollishing ANY port. I wish the LS type heads can be put on an early sbc. We do have these on early type chevs in Australian racing.
huh might be a little off topic but this video got me thinking would rifling (similar to firearms) an intake port make the air to fuel mixture better in turn making a better burn/ combustion and possibly make more horse power?
It would be cool to see after the port of how you'd do it and flow it to do some dimples after to see if it changes it for the better or worse on one that's done right.
Eric 20 years ago when I was racing hydro plane boats we dimpled the bottom of the boat where the water would hit on the last12/15 inches of the boat bottom. The boat was faster by a few MPH. No one could see what we had done. Then we dimpled the top but only for testing. Again the boat was faster. ( we put the same motor on 2 different boats) It worked every time we tried it. We never did run it on the top racing but ended up doing the whole bottom that you could not see standing next to it. After we got out front we just put distance on every lap. You will find the better you can keep the pattern the better your results. Kind of like a golf ball it allows little vortex so the air can not stick to the surface. Rick
Richard... there was a similar technology used on America's Cup Yatchs in the paint finish like fish scales that got you about another 1/2 knot in boat speed, altogether are different kettle of fish because we are taking boundry layer friction not mixture distribution.Trev New Zealand 🙃🇳🇿
That’s correct.
@@dekonfrost7 I know it's correct cause it's true history.
I heard dimpling boat hulls actually creates more friction. With air you get a boundary layer from the turbulence but i think it doesnt happen on water... not sure.
@@blivetsoftruth we only dimpled the botton of the boat that was touching the water when on plane. For our hydro's12'/14' it was about the last 12"/14"
Love the series, Eric. I’m 22 now and have been obsessed with cylinder heads and flow numbers since I was 15. My friends were out playing football and partying while I was trying to build engines and go fast. So glad I came across your channel
Keep up the passion and motivation young man
Pick up a head off an older honda accord ex, f22b1 engine code. They are rumored to flow just as well as the hand ported b18c Type R heads from Japan. I'd be interested to see if this is true.
Wow, a true motor head!!!
Build yourself a small Flowbench like I did in my teens....actually I was thinking about marketing that kit for small head porter's etc Thanks Trev New Zealand😊🇳🇿
@@trevinskiking2165 I made one from a shop vac and manometer.
I've been watching a ton of these. Have a theory about why partially dimpled works better, and where you should partially dimple. A golf ball is fully dimpled only because it needs to be round and it spins. Dimples everywhere don't actually help in a port because its a closed space. Here's the theory:
The dimples actually do two things:
1.) Decrease the available space for air to travel in the port by creating turbulence near the wall. But the air flows over the turbulence with lower friction that it would normally and, as a result, flows with higher port velocity. This is always the trade off you are making when porting: volume vs. velocity.
2.) Reduces pressure on the boundary between the turbulence and the flow. This is why the air bends around a golf ball, reducing the size of the low pressure air bubble the golf ball has to drag behind it.
So wherever you'd like more flow and less volume, add dimples.
Whenever you want to increase the venture effect (around the neck or around a bend) add dimples.
Here's how I used this information: (Porting Buick 350 Heads...very tall narrow ports which is kind of ideal.)
1.) Drew on the inside of the intake port with a sharpie a rectangle. (Where atomizing fuel occurs.)
2.) Drew on any surface where the port was becoming constrained on the SIDE OF THE CONSTRAINT a rectangle about 3/4 of an inch before and 3/4 of an inch after. (If the port bends left, this will be the bump on the left side...or the inside).
3.) Drew a circle on any part of the port where I want the air to bend in that direction. i.e. on the valve guide slope.
4.) Drew a circle on the biggest side of the bowl. (Bowls are all about increasing the venturi effect over the valve seat.)
5.) If I did port matching (Don't make the mistake of doing it to the gasket. Match it up with prussion blue with no gasket.) I added dimples where material was removed, bending the flow in the direction of smooth wall.
Then using a round diamond bit on my Dremel I added dimples where the circles or squares were drawn in sharpie. I smoothed everything else.
I don't have a great flow bench setup, but do have a meter and a shop vac. I had significantly increased flow 15-20% on the first two ports I did at lifts from .200 to .450 roughly. Need to test on a better bench with better flow tools. From a HP/Torque perspective this is ideal as the valve spends the vast majority of the time in these positions.
I'm actually working on the perfect project for this: Buick heads are notoriously difficult to get gains from porting on beyond simply making them smooth and making the neck 90% of the valve seat.
I'm completely against full dimpling unless you want a smaller port. (Which if you watch David Vizzard's videos it actually might be a good way to make the start of the port smaller without having to fill it!) I'd have to check that on a head that needed it, and the Buick 350 heads don't.
I also dimpled on one side of my combustion port! The part between the wall and the valve seat....so the smallest area. So many videos say not to polish this part, that I HIGHLY suspect it needs low pressure on this side to maximize the velocity and as such the venturi effect. My guess here is that air flow in this spot is ALWAYS turbulent with crappy flow, so bending the air over the lip into the cylinder wall is well worth the sacrifice in volume. I hope I don't end up with early detonation, but I'm only running 10:1 compression and the cast iron should run cool enough...I hope!
Hello, very interesting comment, thanks for sharing. May I ask you if on Natural aspirated and Turbo charged / forced engines works the same?
I remember the first time I saw an intake manifold that had "selective surface finishing " done to certain areas. Instantly made sense to me what they were trying to accomplish.... I decided to give it a try on the next intake I ported and the time it took learned me on why everyone else didn't do it... lol. Time consuming...didn't make much if any proft on that job but the customer was blown away and it ran excellent.... when I sat down and figured up the $$$$$ to make this profitable, I knew it was going to be very few that would pay for that level of work on most jobs.... that said 25yrs later I still do it to my max effort stuff.
If you're still doing it the power must be worth it.
Sif you had a CNC it would be almost the same cost
@@muthatrucker6485 the cnc is not free to run, it consumes power, tools, and maintenance and of course it doesn't have a different paying job in it so the opportunity cost is significant.
@@muthatrucker6485 A decent CNC machine that will do this costs around $40k and beyond. That does not include the multi-stage/multi-phase power delivery that is required to run it, the cost of the tools, the maintenance.... and the time required to actually learn how to draw in CAD and do the actual R&D required to find the best pattern to actually increase velocity and provide turbulence to keep the atomized fuel from pooling. Its not easy to setup. Time is money.
As far as I know, there are literally only a handful of machine shops around the world that even offer this process to ANY cylinder head.
And doing it by hand, is not the way to do it because you need to do it in a specific pattern, with specific tools running at specific depths. Its why you can ONLY do this on a CNC and actually be able to show increased airflow on a flow bench at any variation vs doing it by hand and not actually knowing what you're doing like this video shows.
The only way to get an actual repeatable results from dimpling, across and entire range of airflow, is through a CNC machine.
And like the dude said, very few people would pay for such work as in the grand scheme of things.... its almost never worth the effort.
The idea of a teardrop came to mind, then vectoring the ones near the valvestem away gradually near alignment with the v/s. Food for thought.
The dimple intake was something used by Germany's Veicomer Performance a few years back. They had CNCed all the heads and had hard data. It was to limit "Laminar Flow." As I recall, the problem was, the length of the intake isn't long enough for the dimples to make that much difference. It is cool to follow each engine builder's experiment. This is what it takes to find horsepower. Cool video!
its beneficial on two strokes, but even then its only minimal in comapriosn to moving ports, power valves, responsive reed valves and a properly resonant exhaust, one might think that in an airbox design?
it might actuall be of a bit of extra benefit,
It's probably more to prevent boundary layer flow, which is generally laminar, and provides resistance to flow because it is slower.
Isnt laminar flow desired ? Less turbulence.
@@mitchrichard8551 you want to prevent laminar flow, at the boundary. It's a fine line though and is really complicated because laminar flow at boundaries stabilize the flow and can prevent it from separating and becoming turbulent. But with proper engineering, turbulence at the boundary will provide less resistance than laminar flow.
Think about why there is always less wind at the surface of the planet than, say, a couple hundred feet up.
Air literally sticking to shit down here fam, and it's (at scale) pretty laminar.
@@grinchyface thanks
I did this 20 years ago to a set of heads. It gave much better throttle response and didnt seem to hurt top end power. It was alot of work and my hand hurt afterwards for a week.
The reason dimpling works on a golf ball is that air actually sticks to the ball better and increases the pressure of the air behind the ball. It's not much but enough. This increase in pressure effectively reduces the drag of the ball.
The port isn't moving through the air. The air is moving through the port. There's no low pressure area behind the object being dimpled to slightly increase the pressure of to allow for reduced drag through an airstream.
Dimples work on objects with a low pressure region behind them as they travel through the air. Not stationary objects with air flowing through them. Whoever initially tried this made a wrong assumption about what was happening to a golf ball and why the dimples worked. But at least they were trying.
They discovered that shark skin has the ability to form thousands of dimples all over the surface sorta like a golf ball to reduce drag and help them swim faster. Then the Speedo company started making swim suits to mimic shark skin. Then in 2008 they were worn by almost all athletes including Michael Phelps and tested in the on the world stage that year and broke 13 records. Subsequently the shark skin raceware got banned from the Olympics.
@@hellbent7062 same principle.
Its clickbait. Just trying to get some subscribers.
It's been proven to work........
It doesn't. In an optimized port, adding dimples will hurt. In the pockets where air is trapped, you're turning correlation into causation.
To my shock, I saw a Pro Stock manifold from 15 or so years ago, with hundreds and hundreds of ball-end milled dimples. They must have done this work before it was welded because some areas were impossible to get into. Between the epoxy and the machining, this manifold was amazing. I have no idea how well it worked, but it was a work of art!
The changes are within margin of error do 10 more runs with out changing anything and see what the standard variance is👍
This is exactly what I was here to say. It would have been worth it if he had done the test before and after and normalized the test per the differences in each cylinder to separate the testing differences.
Racers have been smoothing ports because that is what works. Dimples are like imperfections and only reduce performance.
Dimple increase speed but greatly reduce effective volume of a tube/runner.
@@TJPDmember this seems to make a ball faster. Not sure on a head tho
@@Mroswaldo16 Yeah, like I said, more speed, less volume. Not what you want really for an intake port.
"Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball's surface. This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake. Scientific American
That is interesting concept. Have to give you the credit because that's how you find out things and you never know until it's proven wrong. Fluid dynamics is very interesting. What about little runners of blades along the walls. I would not know how to install them, but it would be worth trying something different. Good luck with your testing. You should retest 3 to 5 times then average you numbers unless you can really rely on your number for a bass line and result, so you know it's not a fluke.
After reading this… Can we start talking about putting dimples on the rear half of race cars panels?
I think the dimpled principle is worth exploring but a golf ball moving 400 feet per second is different from air moving through a cylinder head under vacuum and with the valve pulses. So they might have to modify the size of the dimples or invert them. But I definitely think it's worth exploring.
@@scottshields8334 tell that to Bugatti
@@scottshields8334 I have tested your hypothesis to see if it could be disproved using the scientific method.
For the test I simply obtained a golf ball and an engine head.
As a control I obtained a second golf ball and an engine head and set them aside under 24 hour surveillance to ensure neither of them was sexually attracted to the other and engaged the other in intimate relations resulting in reproduction of like kind.
I then observed the first golf ball and engine head and compared them geometrically for consistency of design.
Neither of the objects observed displayed any discernible similarities in either shape, size, colour, weight, mass, intended use, common use, form, function, retail price, or resale value.
I'm sure Bugatti would agree.
I was told the other effects of turbulence in the head ports are the better fuel atomization for a better mixture thus explosion. But the flow rate changes are very interesting and great theory. Great job.
I always assumed it wasn't a flow increase but a swirl type action to increase the mixing of air and fuel for increased combustion hence why exhaust stays super smooth
The reason that partial dimpling increased flow is that moving fluid always tries to follow the path of least inertia. The Coanda effect will no allow it to do this, forcing it to follow the contour of the port and slowing it down. The dumpling on the port floor and the back of the bowl create turbulent areas that effectively raise the laminar flow off the bottom of the port and straighten it away from the back of the bowl without fluid-to-surface friction. Think of it as a way of angle-cutting the heads and raising the ports, without angle-cutting the heads and raising the ports. Dimpling the whole combustion chamber, on the other hand, creates turbulence that washes away lean spots and allows you to run higher compression and leaner mixtures for a faster burn without knock and more power up top, making it ideal for open chamber heads that breathe well, but need a lot of timing advance.
I dimpled the intake ports on a methanol burning Briggs & Stratton go kart and it made quite a difference in power. I also found that if a I keep the head temp between 375 and 400 degs it had better response. If I let the head temp get over 400 deg. the piston got too big for the bore and would break the block.
Mike , we did the same on the old flat heads. Eventially moved to punch marks especially on the back wall of the intake port..
i would say that dimples on a carb fed engine will show more increase than in a injected engine... its a matter of the juice being worth the sqwz?
On the dyno it gained nothing. I still have a wka , dyno cammed engine we dynoed that was dimpled. It lost everywhere in the rpm range. Don’t waste your time.
I have done this for decades on FE heads, identically and back into the intake manifold and the same distance from the SSR and the back of the throat. The partial dimple job is the best short of welding the floor. I also angle milled mine to 12 degrees but faced to 13 for the best manifold interface. It is a good alternative on iron heads to welding. Aluminum, I would weld to shape. It is quite surprising that the early 61-65 iron FE head is to the LS. Ford engineering was pretty good for their time. But the dimples when placed as the partial job is can pick up an iron head nicely with only the cost of your labor if you DIY it.
Absolutely, I use them on the shorts side turns to help in pulling the air around corners since air only wants to bend so far.
Cool only partial dimpling, where air needs help? Only the floor of port? Sharp raduis? And the area just before the valve head(also dimpled)?What tool should one use round de-bur-bit what size? And patern?. (GrassRoot racer 4cyl 8v methanol looking for a legal edge)
After watching your video several times, I did some digging/research on the aerodynamics of dimpling. Most of the information I read was over my head but I was able to cyfer a few things from the scientific research from the smart guys.....
#1- dimple size ratio to the area.
#2- dimple depth
#3- dimple edges (Sharp vs smooth)
#4- the angle at which the airstream approaches the dimples.
#5- the correlation/placement of the dimples to each other.
☆All in all, if each one of the conditions listed above is just right, then the velocity of the airstream is increased by the reduction of drag. Like I said earlier, most of what I read was over my head....lol
I'm not sure the human hand and eye can master such percission.
But I'm gonna give it a shot....😂
We would use a tiny carbide ball shaped burr and flatten two sides. The burr was played across the surface, providing a uniform stippling effect. Small stipples induce a smaller boundary layer for the laminar mass flow to traverse.
Typically larger wall deviations will increase the stand-off height of the dead air layer adjacent to the wall. Stippling does reduce structural dynamic drag on mass flow.
I think you are exactly right! I even though about using different sizes to help shape the port funnel to more idea sizes. I think there is a place for bigger dimples: specifically where you want to trade volume for velocity.
The belief is it makes the port act “smaller” by creating a barrier for the air against the wall. My machine can do that but I’ve never tried. It can cause fuel to puddle in the dimples at low engine speeds.
What about in a direct port injection system ?
Wouldn't that fuel boil extremely quickly anyway. The pooling effect would/is a stronger argument with an intake not the head ports
Not many drag cars operate at low engine speeds, right?
You can believe all you want, it simply wont improve anything and all it will do is make you pay at least double the amount of money a proper cylinder head job would be but if you really want it you can go ahead and pay for it.
@@paciencia0956 but are you guessing? This isn't about guessing and trying to find out facts.
The vortices created by the dimples work in some areas and not in other because they help maintain laminar flow and reduce overall turbulence and drag caused by air separating from the surface around tight curves that are away from the direction of travel. Curves that are towards the direction of travel need to be as smooth as possible or they add friction.
Only the bottom of the port needs the treatment.
The rule is if it hits it needs to be smooth if it follows dimple it.
You could also try a series of fine grooves across the floor of the port.
The dimples or grooves only need be near the valve opening just before the curve not the entire floor.
Wow! Partial dimpling was the most effective! I never would have guessed that full dimpling would have detracted from flow. Cool test. Looking forward to the next testing.
without cyl4 numbers we don’t know if the improvement exceeds random fluctuations, as it is below 1%.
The reason a dimpled golf ball flies further is that dimples cause the flow to remain attached longer as air flows from front to back. This reduces base drag. It only makes sense in an engine to add it to the short side radius, helping air to make the turn into the cylinder
I agree with Eric not dimpling the SSR, air speed already increases in that area and if it nears 380-400fps the fuel will separate from the air, hitting the back of the bowl and entering the chamber as raw fuel droplets. I am curious if Eric thinks the eddys on the back of the bowl would help reatomize any fuel that has fallen out of suspension.
Man I wish you was closer to me.. DFW Dallas Fortworth, Texas here
Thanks for sharing this with us 👍
I too thought it was very smart of you to dimple only the low flow areas and measure the results before moving on. What remains to be seen, however, is what the ideal configuration is for the dimpling. How shallow/deep should they be? What should their diameter be? How far apart should they be from each other, on any given row? How far apart should the rows be? There's a wide range of possibilities, obviously, but it shouldn't take a great deal more experimentation just to get headed in the right direction. Once you find something that yields even better results, then it becomes about tweaking THAT configuration a bit to see if even better gains are to be had. I like this a lot. I would definitely try to find a better way to get the job done though. Take a mold of the areas you plan to dimple. Then use that mold to form a thin plate. Carefully mark up that plate with dots, and then use a drill punch on those dots. Now you can drill a uniform set of small holes. Temporarily glue that plate onto the face of your port and let those holes now serve as individual guides for your dimpling. Since all things at this stage are equal, you control depth simply by clocking time. I take it you're using a dremel with a small ball grinder. For each dimple, bring it up to speed and then with uniform pressure press it into a hole for, say, 10 seconds. Who knows, maybe 11. You get the point. Find the right amount of time and then follow the exact same process for each dimple. It is possible to obtain perfect results even by hand if you use the right approach. Also, since you still have the molds from which the first set of plates were made, you can experiment with all remaining ports to determine hole placement and depth. Just make a whole bunch of plates and mark them up differently.
I should have read your post before posting mine. There are many variables and I'm not sure the human hand and eye can master such a feat. But you never know until you try.😂
People have been getting ports to flow within 5cfm of each other for decades. By hand.
The huge intake tract surface finish thread on Speedtalk goes into a bunch of theoretical territory. The most interesting hypothesis is that dimpling creates a series of vortices in the boundary layer which assists in keeping fuel in suspension. That should be dyno tested as almost no one in the industry has something like Siemens Star-CCM to do a multi-phase CFD analysis.
I wonder how wet flow and fuel atomization is affected?
To explain it simpler, air travels faster over air, the dimples create pockets as he said for the air to ride creating a boundary layer and the air in "free stream" then moves faster
Yeah that's why air heads perform better
The turbulent boundary layer is made thicker by dimpling which causes turbulent eddies that act as ball bearings for the flow. I don't know what it works best for... high/low pressure or high/low velocity
An old hot rodder I knew back in the 90’s dimpled the top of the piston, in pretty much the same way. He said that it made the combustion chamber less sensitive to detonation & that he was able to run the engine with higher compression ratios.
absolute hogwash, please never do this
@@ragimundvonwallat8961: you’re probably right, but it would be nice to see some real science directed to the question to see what effect it has, if any.
@@loganshotrod4x464 it you make dimple by taking out material out of the piston the only anti detonation effect you'll get is by the fact that you lowered the compression... but even with that you must take into account that you created alot of ridges...and irregular ridges at that those create hot spot that increase detonation, as a last malus now you have a set of pistons that are all different weigth so you have to rebalance all of that.
as i told you, hogwash, never do this
Those dimples cause a circulation and the air/fuel that travels over the dimples circulating dimples air speed up the air flowing over it. Same effect as a truck bed. The biggest issue I see when people flow heads on the intake side is they dry flow the intake ports yes if it's direct injection then yes dry flow it but if the fuel injector is in the intake manifolds then you need to wet flow the intakes. People argue with me all the time about this subject and as soon as I ask if they flowed it wet I don't get a response.
Eric, I've wondered about this dimpling for a while and appreciate the info you have given us. I'm building a 408" SBM ATM
And from seeing this, I'm going to apply this dimpling to the heads. SBM are already a 18° head stock but the port floors always need raised to really take advantage of this and dimpling may help this in a huge way.
I'm using new magnum castings and going to 2.02/1.62 valve package along with opening the CSA of the pushrod pinch which is a huge choke point on these heads, I'll use bronze filler rod and braze up the outside of the pushrod pinch .050 so I am able to increase my CSA to where it needs to be.
Also since your doing this, would you be interested in doing a magnum head? We would donate a casting and ship it to you for experimental purposes.
I understand it's iron head but your lacking any Mopar head stuff on your page and I believe it would help grow your page.
Let me know and I can send you my contact info, thanks!!!
The best demonstration of this effect and why dimpling can help is what happened when they built the Hoover dam. They first built smooth spillways-tunnels and the water ripped the floor apart from cavitation. We mostly know it as "washboard" on the roads. They remade the spillways with grooves cut in the floor 90 degrees from the flow of water- problem solved. The little vortecies created from dimpling in high pressure areas act as little ball bearings for the air to flow smoothly across. But it has the opposite effect- creating drag in low pressure areas.
I think there's several reasons why this could be helping. Which ever way you think about it, you're getting higher pressure leading up to the short side radius, driving a larger pressure differential into the cylinder and faster air flow.
I'd like to see stepped slots in the same place as the partial dimple. With the same size and depth burr.
Like a set of stairs leading to the bowl.
Leading to step slotted rear portion of bowl.
Recommendation is to just dimple the change of vector of flow ... around the opening and the change in direction at curvature before the valve opening. I wouldn't dimple the first 2/3rds entering the port, just the area immediately before the valve opening. If you can place a dime on a surface and it rocks more than 10 degrees, dimple under the dime, if not don't.
What you want to achieve is a reduction of flow that is fighting the path of flow. Think of it as reducing parasitic loss. Those eddy currents fill the areas that are redirecting flow back against the incoming flow. So your first partial dimpling was a bit too aggressive at the port entrance. I bet you get even better numbers if you do a partial of your partial if you get my drift. And then polish where you didn't dimple :o).
Cool, you recon you can ruin the (dimpling)effect by doing the whole surface area of the intake port? Is it for carburetors effective only?Or would old school 2 valves per cylinder heads in fuel injection form also benefit also benefit from dimpling?
@@nicopotgieter453 It's for ports with high angles to the valves. Yeah it should only be done where the angles change rapidly. Polish the rest.
Don't think ya would 'ruin it' with it totally covered.
Port injection usually adds a significant directing flow. On everything else even direct injection yes. Well maybe not on boost over 4psi.
It's mostly throttle response you make gains ... not so much in power.
We talking about old 300+ v-8 displacements too. Inlines don't have the issue as much with valve angles.
Although i did work on a honda magna v4 back in the 90.s.
@@ejrupp9555 Thanks for the reply, appreciate more than I can express. Fascinating really, cuase no engine the same with differnet setup it seems some stuff work better than other and in some cases nothing at all. Honda WSBK SP2 VTR 1000cc V-twin superbike had dimples on the lips of the trumpets in the early 2000's. At it was Honda Factory HRC team. The injector was on the outside facing the trumpet(bellmouth) though. Like in early N/A F1 engines.
@@nicopotgieter453 So it was in the area with the fastest exterior angle change ... yeah that makes sense. Because in flat areas or negative angle changes (Less than 180 degrees) it is not useful. as the video results suggest.
We used to do this (grooving or dimpling) only on intake manifolds to create turbulence. It is only effective on carbureted and mono port injection as the turbulence helps to keep the fuel charge in suspension (Mixed with the air). We often ran a slightly curved or spiraled grooving to create some cylinder swirl for scavenging.
Porting and flowing can offer significant gains depending upon the engine design or intended use :)
Had a local machinist do swirling in the in the cylinder for snowmobile engines. Also made things like i4 out of 2x i3s.
Cool Idea, did you experiment with fuel injection as well?(Dimple Ports) Was it beneficial in Fuel injection apllications as well?
@@nicopotgieter453 Fuel injection (Port) has a pretty good atomization and fuel/air suspension rate to begin with, so some of that was aimed at promoting cylinder swirl.
So for carburated and mono port injection (sometimes called throttle body injection) the intake turbulence assisted in keep the fuel suspended (atomized) in the air. The swirl direction inside of the manifold has to follow the natural valve and cylinder swirl of each cylinder of the engine.
It's difficult to get good (uniform) dimpling inside of a manifold tube without splitting and re-welding.
In all of our tests we gained a small amount of power and fuel economy, but these gains are not large. You have to think of it the larger picture of performance tuning and all of the other "small" gains you can pick up.
>
A lot of people had a concept of "Bolt on" power at the time, adding this or that to get better performance. I ran with the Phil Irving concept of "removing" what was holding the engine back, often friction, weight, poor tuning (or "Good enough") factory engineering.
Most modern vehicle engines are modeled to some extent off of Phil Irvings race engineering.
Phil Irving: Rich Mixture, Black Smoke and especially Tuning for Speed.
@@nicopotgieter453 P.S. At the time we had some heavy transport department restrictions on hot engines, so hiding the performance tweaks was part of the game for street cars :)
Personally I have nothing against dropping a supercharger onto the side of an engine if it's internals are strong enough to handle 4 to 8 psi boost and the laws allow for it :P
Legally in Australia we can only get away with MAX 4psi boost on certain engines.
@@axle.australian.patriot Thanks for the reply. So fuel delivery near perfect in fuel injection to be of benefit(dimple). Dimpling a band-aid(Carburetor)to get closer to fuel injection. effeciancy. Unless you had an early fuel injected 90's car maybe? Reason Im asking from beginning. Grassroots racer with early Golf 1 1600cc 8v (U-Flow) methanol. Trying to look for hidden horspower. Even if is.1-2%.Is fuel injection though but not the most powerful even compared to other competition 8v fuel injection from same era stock or modified(more powerful than Golf 8v U-Flow). The Golf U-Flow alwas a smidgen behind in HP game(in my 8v 1600cc 4cyl racing class)
I guess the variables to play with are 1)the size of the dimples 2) location/spacing 3)Depth..
Somewhere around 20+ years ago, I read an article in a magazine dedicated to sprint cars about a shop that built sprint car engines doing dimpling. Their reasoning was that dimples on a golf ball make it fly farther. Maybe it works externally but doesn't increase air speed inside a tube (runners are basically tubes). They didn't go any flow rate numbers, before and after so no proof of increased flow was proven.
Like the theory then testing to prove what works. Answered several questions I thought of and you tested several of them on the flow bench with results.
We always left the intake surfaces a little rough not just for flow, but because we were using a wet nitrous kit the rougher "hatched" finish kept the fuel from pooling up in the port.
Pure wizardry! Fantastic information and I am glad you did partial dimple using your slowest part theory.
This is an old subject, but what about the benefits/negatives of D porting?? Be a cool real world test to see.
Thank you for testing this. What about ruffles instead of dimples? Water and air react similarly. I used to make Berkeley jet boat castings. They used the Bernoulli principle to greatly increase water intake volume.
You can test it by dangling a spoon under a slow running water faucet and see how forces the water into where the intake would be after the spoon.
Raise the floor of the port. You can fill it in with epoxy. Increase the radius of the short turn and raise the roof of the port to to match the floor. Maintain the bias of the intake runner but you can make it wider if there’s enough material to do so.
The guys on Mythbusters dimpled an entire car and it reduced aerodymic drag. Dimpling should help. Now to watch the video!
The dimpling would increase fuel atomisation on a mixed air/fuel intake ✌️
I believe a lot of it will be the help at low speed/part throttle where the fuel has the chance to touch the wall.
@@PantherSerpahin same, I remember back decades ago there were intake gaskets with screens in them to help keep fuel atomized. No idea how well it worked with the trade off of better atomization, at least in theory, to the reduction in theoretical port size.
I think a uniform pattern of the dimpling is paramount for it to work effectively.
I’m used to fooling around with old iron heads. All I’ve ever known to do was clean up the rough castings and gasket match the intake to the head. Very interesting gig you got going on here.
U know way more then I could ever know about this stuff. So ill take your word for it and seeing the data helps too. I just built a decked out stroker big bore and ported out 4 stroke atv. And I thought about doing the dimples on some of the intake but decided against for lack of data out there. Deff much appreciated man
That is exactly what I have seen. I only dimpled the weak spots on an iron head. It improved just as if you were able to fill it with weld. The dimples on the FE head worked really well, but it is in selecting the area by listening to the flow bench.
I know Smokey did it in the 60’s with a blunt center punch until Nazicar outlawed it. He also dimpled the dome but he did smooth them out to prevent hot spots and predetonation.
HA! Nazicar...funny, you just made my day. Thank You. There were quite a few innovators in stock car racing. Just couldn't get by the people who didn't know much about racing, just how put on a show they thought the fans wanted to see.
The punch actually raises the material around the hole , I do this on all my two stroke porting.
Get someone on here who does cfd. The dimples would be more effective if they protruded into the boundary layer. Since its turbulent flow and not laminar protrusions into the boundary layer will have more of an effect than dimples.
Im so glad i watched this video! I have started an experiment with a RTC-15 Predator 212 head. With such a short port to begin with i thought and thought on how dimpling could affect flow. I did as you did, starting at the opening of the shortside floor being more aggressive. As i went towards the bowl, i put more distance between rows , AND reduced the size of the dimples. I just had a hunch this would be the ticket. I havent dimpled any of the bowl area (as of yet) Questions: 1. Should i hit the backside of the bowl? 2. Should i dimple any of the intake tube? Keep in mind this head already has a pretty aggressive bias swirlport and it really puts a good swirl affect on the air. Ive put smoke through several of my heads, AND with just my standard bias swirlport see unconventional gains in power. Its amazing the power gains im seeing all across the board! Especially mid to upper rpm range! Thanks!!!
BOY, do i enjoy your tech......i thought ur intial idea on the dimples was rite on, i thought FULL dimples would ruin the venturie effect, and i was right, and so were you!!...i look fwd to ur next vid on the valve job.....i have learned ALOT from ur vids......i'm the bracket racer class advocate guy from the other day....GREAT STUFF!!......btw, i'm at 10:90's now on pump gas, 462 cid Pontiac, Kauffman Racing heads.....lookin fwd to ur next vid!! TY for ur sharing of ur expertise, and if you told us all ur secrets, you wudnt have YOUR race cars, so, keep certain shit to URSELF FOR SURE!!
This is good for long stroke engines like yours and the Olds and the 4.25 stroke FE. :-)
@@notme810 HA!...i may try, but I wanna get the best program first outa Kauffman.....i have the 310 cfm program now, they offer a 340 cfm program on my heads, i think they have a 360 cfm as well (i have their D-port, with a modern chamber) i went from 36° total to 31° cuz the chamber is so efficient.......i'd love to do that first, then talk with Jeff (Kauffman) on the dimples......he's a great dude, down to earth, and ALWAYS responds to my e-mails......TY sir, for the input....i can see how my 4.210 stroke cud benefit from the tiny eddy's.....creating even more velocity, to help my V/E Get up there around 100% if not more!!....TY again!!, seems subscribing to the channel, has already reaped nice benefits, from folks like you!!.....btw, i've built a # of FE's at my shop, they sure are some BRUTES, i tell ya!!.......
thank you so much mate for making this vid ive allways wondered this seeing how mythbusters did the dimple car
can wait to see how it go's mate
thanks you
What a great way to trap carbon deposits.
My explanation would be that the dimples slows the air down on the inside. It helps to stream the air trough the corner. (You trip the air the right way)
CNC can make a pattern, that was designed in a controlled environment for even better flow.
Exactly. Only a well researched and tested CAD file, using extensive fluid simulation - is the absolute ONLY way to get a dimpled manifold to work. Doing it by hand NEVER yields the same results that actual machine shops that offer this work that have been doing it for 20 years.
If you look at the Veicomer videos, their dimpling method is the same across every single cylinder head and there arent as many dimples and are much larger and smoother. This guy just used a dremel with the cheapest bit - no wonder he didn't see any increase
what we did was take a set of 202 angle plug heads ported all ports water, oil drop, valves to 204 and ported the intake and exhaust plus had to port the intake to match the heads . we wanted cast on cast on a pro built 327 for high rpm engine for pump gas only . old man bell built it i just helped learned a lot from him . i have had the engine to 15,000 rpms many times has lasted over 20 years of street racing ,cruising and just driving it hard. was the fastest in my area on the street back in the 90's for about 3 years with pump gas only . it pushed over 1200 hp just pump gas 13.5 to 1 compression with a tunnel ram started with rick news dragster engine and built the shit out of it . even seasoned the block polished it over size cylinder walls what bell calls supper stroke it . he called it a indy block with a dragster top end
You should see the biggest flow increase by dimpling the short radius only. Well, maybe just the short (or bottom of the port). So basically the partial porting you did, MINUS the dimpling of the bowl PLUS dimpling of the short radius. Golf balls are dimpled to make them travel as far as possible through the air. If the surface of the ball was smooth, the airflow around it would detach early creating drag on the back side. This drag would effectively pull on the ball in the opposite direction to its flight path. The dimples disallow this early flow detachment greatly reducing said drag. In other words, no dimples, the airflow detaches somewhere shortly after the equator of the ball. With dimples, the airflow remains attached to the spheres surface well into the back side. Thus, the air is better able to follow the balls curvature in full. For cylinder heads, this means more airflow as the air pressure past the valve on the short radius side is often lower than the opposite side. So better airflow, and potentially even better fuel atomization than more cfm alone would generate. Oh, and the dimpling of the top side of the port basically causes more resistance to the airflow since the air is colliding with a concave surface that is not smooth. So dimpling on convex surfaces...yes. Dimpling on concave surfaces, maybe not. Flat surfaces are somewhat indifferent I feel. How do I know this...? I studied the mathematics of fluid mechanics in graduate school :-D
This principle is what makes a golf ball fly so well.
Cheers captain obvious
Dimpling gives only 1-2% better flow. More power is hidden in size and shape of port and valve job. But if you are looking for that last 0.1% of power gain it's a good mod.
It’s about creating turbulence to fully mix the air and fuel droplets. Most tuners doing porting polish the exhaust but leave the intake rough.
Really appreciate the time you spend on these videos. Apparently many others do, too, as you are growing a healthy subscriber audience. Congrats on that.
It would interesting to create dimples in the floor by impacting with a hammer and punch. This might create a small ridge around the dimple. Helping to raise the floor a bit.
That is how it was done back in the 1960s.
Interesting but myself I polished my intake & exhaust ports I had the exhaust ports as smooth as glass the intake ports were final sanded with a 120 grit sandpaper then I sandblasted the intake ports washed out the ports to remove the sand grit then compressed air to dry and blow the clean and it worked very well it keeps the air / fuel mixed all the way through the port . . sometimes old school is the best and won't destroy an expensive set of heads
I have had great results with a Newen seat cuts on the valve job. Average increase has been around 12 cfm on intake. It incorporates the pressure recovery into the cut without a second setup which reduces error.
It would be interesting to see a stock sand cast iron head done with the short side/s left as cast, other than any obvious ridges, and the rest just smoothed out without trying to go crazy on the modification.
@@mctigmctiggy1475 even thought it ain't like it was back in the day, there are still folks who do.
I would expect dimpling is mainly done to prevent people sticking the head on a Rottler or Centroid mill and copying it so easily too...
You should try WPC treatment on the inside of the port! They say it reduces friction significantly but maybe they just mean between two metal parts… idk but would make a fun video! Love the content! Keep it up!
WPC only benefits parts where there is friction between two parts, such as a rod and crankshaft, or the wristpin and piston. WPC treating a cylinder head has zero benefit and a waste of money.
Anti-friction methods do nothing for airflow
@@rotor13 Oh man someone has already tested it? Could you point me in the direction of the recorded test results?
This is interesting to me, because those little eddy's wouldn't they create turbulence and in turn give better air/fuel mixture🤔🤷
Same cuz that’s how a golf ball works
No at best a few grams of material loss is going to have more effect. With direct injection I would say 0 effect at all with port injection just pits to collect garbage in imho.
No extra air is going in mix will likely be worse as the pits would serve to collect fluid l.
I dont subscribe to much of anything, but u sucked me in with this particular head port experiment....i gotta know!!...TY sir!!
I almost did full dimple ty so much appreciate the help you saved me ✌️
Did you get to study the airflow around a golf ball due to the amount of dimples and lift that it can get ?
My question is how does the liquid-Fuel react to the dimpliing and would I see the difference on the dyno of the best results of partial dimples. Thanks
So what I believe is that as air goes thru the ports that are dimpled we get more turbulent airflow , so when the atomized fuel is injected in the port and goes into the cylinder to be combusted the air fuel mixture has been mixed much more efficiently that other methods, theoretically it should work like that lol
Do you mean atomized fuel,as in carb/MPFI application? Large drops of unatomized liquid is bad juju.
If the demples improved Volumetric Efficiency, then it increases power output or lean out your current setup.
Only dimple on the lead-in to a short side with divergence greater than 6°. If it's parallel, converging, or diverging lass than 6 then leave it smooth.
Golf ball effect. Very interesting data, thanks
Very interesting. And smart thinking with the partial dimpling. Makes alot of sense 👍
Id like to see the one of the racier 45 in comparison to the 50.
So where is the best place to put the dimples and where should we stay away from. Salt Flat Runners sometimes do the same thing but they leave certain spaces polished🤔
Full dimple reduces port size via boundry layer think golf ball provides lift and reduces resistance around ball but increases surface area shrinking port size due to enlarged boundry layer. The partial behind valve and on floor good and you proved it as little flow takes place there and more boundry layer in those areas improve flow into valve pocket and combustion chamber.
You are exactly correct about the eddies. What you described is lamener flow.
pretty interesting. I wonder how this will be affected if its polished after dimpling... We need to make you a port dimpler :)
Exhaust valve: on the face of the valve, the part you see in the chamber. Round the edge of it so the air can navigate around it and get into the port easier. I chuck it up in a drill and do it by hand on my bench grinder and then my belt sander. It’s usually good for about 5cfm almost everywhere.
different, would it make sense to have a dimpling setup plate made on a waterjet, or lazer cut from say 16ga steel that could be formed to the bottom of the port to do a partial dimpling, and have more consistant dimples? at least it would be a parameter of this to try.... you could also trim the dimpling plate to fit your application/port and specify a size ball burr to be consistant... I imagine the eddy being created in the port hinders/restricts flow/volume especially at higher rates. I find the idea of port design interesting, and am enjoying seeing other designs & ideas implemented.
I run a small CNC shop with 5 axis machines, I've always been very interested in engine building but never had the time to get into it, this is something I've been wondering about for a while. As someone with lots of 5 axis machining experience this would actually be super easy to do with the right machine and software. Side note I'm always shocked at how poor the surface finish is on CNC ported heads in aluminum it should be easy to make them looking like mirrors, I always wondered what a mirror finish with dimples would do.
Mirror finishes typically create boundary layer restrictions.
@@actually5004 sorry what are layer restrictions? And wouldn't dimples fix that? Golf balls are super smooth, I'm assuming for a reason.
@@85CEKR The boundary layer is an area next to a surface where the flow does not separate from the surface but clings and drags across. Dimples would typically fix that, but the rough surface finish on most cast heads is enough because for the dimples to be effective, the air pressure needs to be higher and the velocity needs to be lower than conditions in an intake runner.
@@actually5004 thanks for the info
I'd like to see the same test done but with a dyno as the fuel atomization may be better and give better results with a full dimple...
Thanks for the tip 👍 I think a clean 45 degree valve job would be best for the next video
10 months late and maybe it’s mentioned in here but the dimpling should make for “slipperier” port. The air “sticks” to the surface due to friction like any other solid or fluid. I remember a segment on Top Gear when they highlighted the air channeling on the Ferrari F12 how it’s send down the sides of the car which creates a boundary layer of air for air flowing around the car to slide against and therefore less drag. Same idea, bigger boundary layer, more air “lubrication”…more flow. With the partial dimple you had more flow which more or less proves this. The full dimple shows less flow and if I followed correctly the “full” had the dimpling down by the valve. The decrease is probably due to some reversion which is due to the added boundary layer and turbulence in that area. Idk just my 2¢ taken from what I learned in Fluid Mechanics in college
Looks good but want to see dyno results before and after to see if that work
Ooo my bad it's there so partial work better
We always used a special tool that put a very coarse surface around the port or perpendicular to the airflow.
Like very coarse cone
Not talking about sand paper now.
The surface ends up feeling like sandpaper you cannot use sandpaper to produce it.
You would have to put a million dimples in that port to make the same effect.
Like peeing the surface.
It must be "regular" and minimal in relation to it's size like 1 to 100.
If diameter is 2 the roughness should be . 002 in proportion but must be regular.
Reality is it's the change of direction where you must have the detail.
We always treat the entire surface.
For sail boats they make special plastic dimples that come on the sheet makes it much easier to apply.
The only place you will see a detail on a relatively long flat surface is on the departing side meaning two surfaces at a slight angle to each other just beyond the point of the divergence surface roughness causes the fluid to remain in contact with that surface, 5 degrees of changes is already enough.
Oh by the way air is fluid, air with anything entrained in it has more density and inertia.
My friend dimpled his Cleveland 4V intake ports 20+ years ago. It increased power across the entire rpm range.
The whole port or partial dimpled? Intake also(dimpled)?
I remember seeing combustion chambers dimpled like this, in Circle Track Magazine, I think way back in the early 90's.
I have heard dimpling the intake runners makes more difference than the heads.
The boundry layer is almost always going to be around .100" thick no matter the surface, it's simply near dead air, the closer to the surface, the slower the air moves...
Held in place by the intrinsic electromagnetism of any material that holds a different charge than the adjacent materials.
The premise is to loft the mixture over relatively dead areas of the intake tract, I have done it to plenum floors also. The Ford FE is a great garden variety head with CJ valves and even 2.19 5/16 stem intakes to get over 600 hp with. Aluminum welding is better, and less labor intensive. But if a certain casting is required and this modification is allowed or you just want to mess with people. Lol, why not?
Love the video just a little confused at 5:00 you say you would’ve filled these areas up with epoxy on the partial dimple, but why if the partial dimple yielded the best results
subscribed......new favorite channel. Gonna have to get a set of heads from this guy
Much obliged Sir for the insight,
I'm interested in the partial dimpled port specially the port entry lower floor, any insight on the affects on airspeed,
Did the lower floor airspeed increase?
Did the air speed variation from the upper wall to the floor became more uniform, emphasizing the area from the port entry till .5 inches before the short turn?
Very interesting investigation video, you're quite right about the effect on boundary layer and that it would increase the air velocity by narrowing the effective passage.... But I don't see that it would increase total airflow.... Isn't the whole point of port polishing to maximise laminar flow, i.e. the opposite of dimpling? Then again I would expect dimpling around/after the injectors to help with atomization. I'm no aero engineer, but I guess to get this right you'd really need to do some modelling in solidworks..
that old english guy david vizard has the numbers. he has 60 years of head work, from F1 to Nascar. He does mention the golf ball dimpling of ports but never reccomends pollishing ANY port. I wish the LS type heads can be put on an early sbc. We do have these on early type chevs in Australian racing.
huh might be a little off topic but this video got me thinking would rifling (similar to firearms) an intake port make the air to fuel mixture better in turn making a better burn/ combustion and possibly make more horse power?
It would be cool to see after the port of how you'd do it and flow it to do some dimples after to see if it changes it for the better or worse on one that's done right.