Porting vs. Polishing vs. Both
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- čas přidán 21. 03. 2018
- PORTING AND POLISHING!!! People have been doing since car’s have been around. This was more of a thing back in the 60’s and 70’s where you would see this happening on carbureted engines. Even though cars nowadays are fuel injected, you will still see a performance gain by doing this process to your aluminum / steel cylinder heads / manifolds.
Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve the quality and quantity of the air flow. Cylinder heads, as manufactured, are usually suboptimal due to design and manufacturing constraints. Porting the heads provides the finely detailed attention required to bring the engine to the highest level of efficiency. More than any other single factor, the porting process is responsible for the high power output of modern engines.
Cylinder head polishing refers addressing the imperfections in the casting or during the porting procedure. The polishing stage is where you will get the last 10% of power and efficiency. It levels out the high spots to make a more uniform and consistent finish. By doing that, it allows the air to flow much faster with less resistance through the port. Depending on your fuel system, you will want to either polish to a brushed finish by stopping the refining stage at 120 grit, or continue to to a pull mirror polish finish.
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Just my two cents but you can argue till the cows come home on the theories of flow verses velocities, this young man is definitely on the right track but my comments are on the quality of his video work. Great production quality and concise and articulate narration. He has a future, a great future in this kind of work. I have subbed. Coming into my golden years now but I can say that I have raced, won,lost,built, blew up and destroyed just about all of it and had a great time doing it.
The point of porting and polishing is to create an air flow that is as laminar as possible. Anything that deflects air molecules from a straight line of travel, reduces flow. As the molecules speed along, they reflect off a surface at the same angle they strike it - think pool balls with no spin on them. The angle of incidence = angle of reflection. Your task is to provide a surface that will deflect each molecule by the fewest degrees possible. This means no rough edges that will cause a radical change in direction. Creating turbulence is bad because it changes the direction of molecules, which in turn collide with other molecules increasing the effect and causing pressure which reduces flow. Atomization of fuel is never a problem because the air will be plenty turbulent by the time it passes the valve, and it is entering a very hot environment. The mistake many make is in making the port as large as possible, but creating bad angles in the process and causing restrictive turbulence. When porting, think of microscopic BBs being shot through the port, and how the surfaces would disturb the path of the BBs as little as possible.
Laminar flow is a virtual impossibility given the geometry we're dealing with.
Laminar flow through relatively straight runners. It's a non issue at the point of turbulence
We are not talking about surfaces that are so rough in an intake making much of a difference to worry about them or worth talking about them, what is important is making them as straight as possible and paying attention to volume trying to keep large to small as you enter port. Spend time on blending or removing things like vlv guide that stick into port, make a smooth turn radius where port turns (never get a straight port), unshroud port where meets bowl and give a good valve job. In my experience unless racing and you have to use specific head not worth paying for porting one (or doing yourself) when you could buy a better flowing head for about the same money.
As someone who hones their knives with sandpaper of very fine grit, 5000 at minimum as a finishing grit, on a bock of marble or a slab of glass, depending where i do it in my house, I will definitely go manual mode with my ports, as there are no electric tools that guarantee the quality and safety that a hand with wetpaper does, also, you can feel everything and can therefore get the most nominal shape with least curves in your work, whereas with power tools it may look great but still be uneven to the touch, and the air at high speed will notice even more than you will by hand, but then, thats why we polish it with powertools... Also, polishing my friend is the step done with the polishing paste and cotton pillows, so dont say that you are polishing it roughly, as polishing implies a mirror finish, that is why you can polish metal with powertools, as polishing can not create a hole or remove a bunch of material... Sanding or cutting or abrading away is what leaves "brushed" look and finish and that is done with sandpaper, powertools that use sanding bits. The porting is the roughest cutting with tools that do not abrade to cut but rather use a physical blade of whatever scale to remove thin layers, be it diegrinders with carbide cutters, dremel tools or any other highspeed rotary device...
Knock off mold lines/ sharps, port match if needed and run a 80 grit sanding wheel.
Anything more and you need a flow bench.
I paused at 6.49 just to say.
My question was "I wanna go fast, Ricky Bobby fast, I'm real serious about it"
this great man says to me "that's all great in theory, but heres what we run into, come take a look"
you myguy earned a subscription
By far the most compleat video about port n Polish thank you
Some of the best engine builders have said “Port finish doesn’t really matter, just get the shape right”.
Who?
Eric Fixalot exactly it's TRUE
There was a bloke out there once upon a time that used to somewhat randomly tack weld his cylinder heads/air paths to the heads to create tumble in the airflow and he used to get mythical results.
Not sure who or how, I'd have to ask the old man.
My only reckoning is that the volume would have to be similar volume/pattern for it to produce good results on multi-cylinder engines.
My understanding is it's (abstractly) a bit like shark skin and water.
That's for carb'd engines.
If you want to know more I will ask the old man when I see him next, just send me a direct message and I'll send you any info I get.
Of course we would like to see the next video.
Nice man hope you get this beast finished soon ✌
awesome very in-depth and educational thank you
We found best results for our heads; cross hatch semi rough on intake and mirror on exhaust. Size was tailored to horsepower/torque curve desired. With the new injectors in market where we can change injection angle will change our approach quite a bit.
100%
Was waiting for this video... very nice
Awesome introduction to port and polish. I’ll be doing this soon. Thanks.
You can't be serious??? Who is dumber? The person that makes a video that doesn't have any real experience,? Or someone that watches the video and takes their advise?? Casted?? Really??
I felt I’d practise. Learn. On an engine that isn’t to be used. Test it. Then when I get aluminum heads plus a ton more education on my part I’ll probably think about doing mine or find a performance shop. I did my cr500 Honda back in the day. But one cylinder is easier then 8 and mine was obviously 2 stroke. Left it rough.
Great video!!
awesome videos man, im learning a lot
Your not hey's a fucking idiot
Your videos are awesome
Excellent video, easy to understand. White board, works well.
Awesome man was waiting for this video since the last one you posted of the block. I asked about the port and polish vid and you said it's on the way :)
Ohhh yeah don't you worry :D
Post a video when you do yours so I can watch you duck your shit up to LMFAO
This is such a nuance subject. There are SO many variables that will change depending on the application. For example the induction system, the purpose of the application, the types of camshafts used in the application.
In a street application, the low end torque loss, in my opinion, might not be worth the gains up top. But even that theory does not apply to every motor.
Like I said, every application has Sooooo many variables.
Very informative this video just helped me. Got my head back from the machine shop and was wondering why isn't my intake port polished just ported and got that brushed finish. I thought it was a bad job lol
Matched, ported and polished was POWER for engines Pre 2001! It was also CHEAP! The blocks are totally different! Made for fuel economy now
Yeah, I'm doing my 1995 S Series with .20 over and 3rd gen crank and tie plate, etc dual intake cams, etc, not all the mods but yep, you would be correct. I know the difference between even the earlier Saturn engines vs the 1999-2002, even though technically the same engine, the later years, the put roller rockers on the head, but used smaller intake ports and added all kinds of emission restricting features to the exhaust manifold, etc, u can't even find a header made for the 1999-2002 years around. I have a 1995 and a 2001 SL2 in my yard that is going to be the donor car for the 5 speed manual for my 1995 SL2 amd going to add a MFactory limited flip and lighter flywheel, etc.
Injectors play one of the biggest role in how much turbulance is needed. Certain race setup may do close to mirror due to the fact of forced induction. But these are high revving big turbo setups litterally where size matters more than finish.
After so much pressure velocity is hardly the issue, afterall if that was the case intercooler and boost piping wouldnt be smooth.
Na cars depend on velocity similar to how their back pressure helps their powerband efficiency.
But a car can be built in many ways so pretty much anyones argument is valid.
Great video and very descriptive. Came by this on accident and figured what the hell.
Great vid 👍
Great stuff!
Glad you think so!
For all those who think they know check out engine masters. They don’t show how to port and polish but they test on a dyno and debunk all these stupid things. Port and polish all of it. Higher volume means less struggle which totally out does velocity. When you have velocity you add pressure. If you want to prove volume out does velocity just blow through some tubes of different sizes. The engine will get what it needs. Port and polish gives it that easier allowing the engine to not work as hard to breathe
I had mirror polished heads on port injection and made 30hp on the dyno all motor 3.0L 3000GT. Kids a want a be. You can also buy over size head gaskets to port the combustion chamber larger, and you can make your own intake gaskets to port it any size.
two thumbs bro! interesting.
I always heard from the old engine builders, port the intake, port and polish the exhaust. You want a rougher finish on the intake to help atomize fuel.(carbureted engines ofc)
Leaving a little roughness rather than polishing to a shine is most beneficial
Rough and smooth for different applications
Gasket matching is a thing and its usually done in older engines, new engine use that new type of gasket
Shared and liked your video
Love the explanation. Thanks buddy
Nice video, reminds me of engineering explained style
Don't be fooled, engineering explained is actually an engineer, and he has done engineering work. I'm a mechanical engineering student, so I am not an engineer, but I know enough of fluid mechanics and aerodynamic (which I both passed with great results) to know that this guy does not know anything about actual aerodynamics. Most mechanics think they know, but they know from experience what kind of works and what not. Only an engineer (like the one who designed the engine) understand the aerodynamics, only the production process and cost cutting can come in the way, so that's where improvements can be made. Leave it to a real engineer though, or at least an experienced mechanic or tuner.
👍👍 nice man very nice
There is an abrasive mud than can be pumped through with great results. High dollar castings are surfaced that way.
JUst my two sense, if you make it too smooth you create an area where the flow sticks to the side, known as the boundry layer. Ruffer creates a faster flow because there is little to no boundry layer close to the surface, sailors have known this about fluid dynamics for centuries
Most new direct injection engines now have both direct and port injection both now...so it keeps the valves clean 2018 and up.
I have been using the shark skin finish since the 80s. Only on the intake side though. It will take you some time to find the right kind of stone to achieve it thought. I use a brand called cool stone. Used in dental work.
Leave the oem "cast roughness" on the intake ...polish the exhaust if you want to polish something.
Is it safe to polish the head's combustion chamber surfaces on a direct-injected system?
That's a great video, perfectly explained, well done bro!
Rough and smooth on exhaust port
The receiving side should be larger so as not to cause back flow and what others have said if you don’t flow test bench your guessing ,cleaning small imperfections I agree
It's all about proper velocity to induce a tumble/swirling effect.
Porting good. Polishing chambers and exhaust ports good. Keith Black found 6% hp increase over entire curve with chamber/piston polishing. Polishing exhaust ports has a small gain, but mainly keeps carbon from sticking. Polishing intake ports is a waste of time. Wet flow happens in both polished and ported. Focus on velocity and swirl/tumble.
Ahem......most all OEM & aftermarket racing suppliers / experts have already spent the time, money, & have done all the R&D work for you.....save your money and just buy the "go fast goodies" they already provide, be safe, & have fun....but that doesn't mean you shouldn't learn and understand it, especially if you are on a design team, need that extra little edge as a privateer, or are in a niche class such as antique / vintage / classic, etc.........by all means.....1. Study, Study, Study (Air / Fluid / Thermal Dynamics, Geometry, Boundary Layer, Flow Bench, Dyno, modeling software, CAD, etc, just for starters). 2. Always make / save more money, you're gonna need it. 3. Determine the end result you really need & know your limitations before you start. 4. Obtain all component blueprints if possible, but accurately measure all stock components regardless - get your base line (Flow Bench, Dyno, & mock-ups are a must). 5. Talk to an expert in your OEM / Aftermarket fields......take extensive notes. 6. Go "pick" the local junkyards for some cheap stock parts that you are already using BEFORE hacking on & ruining your good parts. 7. Measure, flow bench, practice, flow bench, practice, practice, flow bench, dyno, document....destroy some shit, DOH!....start over....flow bench, practice more, dyno, etc (but remember failure = learning). 8. Spend money (make more & save more). 9. Test runs / proving grounds - reliable consistent results? something else gonna fail because of these gains? 10. Modify your good parts and go hit the track (or street, dirt, air). 11. Retain & document everything you've learned, but always remember and accept that what you accomplish now will most likely be obsolete very quickly, something or someone faster always comes along........if that's a problem - then create a niche class, or master a specific application, and be unique.
Put dimples inside the runners... Like a golf ball. = Golden
Good vid.rough port works like a golf ball,all the dimples have air in them allowing the in coming air to pass over it smoothly.any sharp edges in and around combustion chamber and ports creates hot spots,radiance all corners to keep heat down.and don't go through to the water jackets when porting or you will end up with water injection too
Thank you for the great explanation 👍🏽
Actually it depends on the fuel delivery. A rough texture is typically better for a carburetor or Throttle body configuration. Port fuel injection a smooth polished works best. Keep in mind biggest doesn't necessarily mean more power.
Research that particular engine, and find out where is the choke point. That may consist of intake manifold or the exhaust manifold. Some engines you could loose power from over porting.
Dafuq u tokin about throttle bodies are fuel injection
@@seventytwo4728 Old throttle body injection for example Gm crossfire injection system. A newer style multi port injection where you have an injector nozzle for each intake runner.
Lets get this motor back in the Mini
Sounds fun
Hiya milanmastracci. Once you start putting the mini back together are you looking to install a oil catch can? (Which i think i would go for) Or a pcv delete? As if you don't you will surely get carbon bulid up again. P.s. love the vids. Your amazing at what you do.
Smooth is like watching water roll across a windshield with rainx on it. Fuel needs to break up and tumble on a rough surface with the correct shape for maximum velocity
Try to get the air to be not turbolant. It is impossible
A fluid mechanics class would make everyone realize that polishing is not detrimental.
Dremel Tools which is handy power tool ,works great alternative best option than drill .
In a port injection setup, do the valve seals wear out quicker?
Love your videos, Milan!
u sound like you have a bmw
Sorry but there's so much wrong with this I wouldn't know where to start! I would suggest some SAE white papers on laminar friction factor equations to relative roughness values. This will help you understand boundary layer ratio thickness to relative Ra height. Also how the viscosity of the air and its environment effects optimal port Ra. Intakes with boost should be limited to 60-80 grit, far from a mirror finish especial on the intake side with a limited flow velocity of around 700 ft/s. Exhaust on the other hand is quite stable to 1300-1600 ft/s and our gas is very viscous at 800-1000C due to the density change and speed of sound in that environment. for these reasons mirror in the best finish for exhaust. Another important point that seems to be missed is, porting has nothing to do with making a big whole! its about velocity matching. finding the chock points and balancing flow. I've done and been involve with countless back to back test over the last 20 years with our race heads and plenty of others. On most late model twin cams, there's very little need for added CSA. They do not need any increase in window CSA, some actual need welding up. The ports or intake MCSA's is what needs to be match to improve engines VE's. Valve throat size should be similar to the port window CSA if you want good area under the curve. This video is very naïve and shows a huge lack of understanding in the very basics of physics around air flow and its function and science behind a good port design.
Thank you for this comment. This video is an EXTREME oversimplification of port and polishing. This young man speaks confidently about this process! If I didn’t know any better, I’d think you’ve been doing this for years.
First off, I’ll give you credit for making a video that covers the entire port and polish process. I mean that. I have mad respect for people who post stuff on here that attempts to help the masses.
I’ll stick to the biggest issue I have with your content in this video. In all my years as owner of a automotive rebuild and remanufacture shop, I HAVE NEVER heard of a cylinder head being ported and polished a certain way up until the point of the fuel injector, then done another way after the fuel injector. My company port and polishes every engine we rebuild/remanufacture, and have not have any issues to date. If you have data that supports this method, I’d really appreciate it. Thanks and good luck.
@@thatoriginalguy Yes that seems to be the problem with lots in the industry, They "believe" so much that isn't based in any facts or physics. It's not an over simplified video, it's plain wrong.
You are spot on sir, young lad here doesn't understand certain things.....you cant just open it up, you SHUDN'T polish (persay).....and he doesnt mention reversion at all (he probly dont know what that is).....if you do certain things to your exhaust port, you will enhance reversion...WHICH IS THE LAST THING one wants in getting a nice % of VE!!........ah youth......boy, give em a smart phn, and all of a sudden with have a genius......UGH!!
I have a little tip for you. When you're trying to educate people who are much less knowledgeable about a certain subject, then don't use acronyms or at least explain what they stand for. When you use big words or acronyms, only people who already know what you're talking about will understand it and it goes over the peoples head who could actually use the knowledge.
The man is just explaining the process as well as the benefits and drawbacks. Obviously he's not a genius on the subject matter but he knows enough to educate other people while you see fit to put him under scrutiny because "he didn't do it right" grow the hell up.
What about carburetor? Should I polished it?
Use a water-meth system to help clean your motor and get performance on the cooper
DO you think that we can mox polish in oil motor ?
When are you going to cover dimpling intake, exhaust runners, and combustion chambers?
dimpling isnt really viable, only creates unneeded turbulence.
If your intake manifold is plastic, it's smooth already, and there's no need to polish it.
Hog it out good!
You need to make the ‘combination’ not just change one thing. That head is a late model design optimised for street duty, porting it without changing cams, intake, exhaust, compression, rev limit and tune will drop the velocity. More flow always requires the combination to be optimised, that’s why the turbocharged method is best, no porting required.
First thing I will say if you do not have a flow bench and can actually test things is ONLY GASKET MATCH. You can ruin a set of heads or intake hogging it out without flow testing.
You can port the hell out of a poorly designed plastic intake. It is easier to grind than anything else.I wanna see flow bench numbers to prove me wrong or OP admit you spouting off internet crap you read.
Here is your kicker. I have a flow bench. I've played with plenty of heads and intakes on all kinds of racing crap since 1987. Go carts to 1200hp v8s.
What you are spouting off is so generic it is almost old school, even then it's only about 1/4 right.. welcome to about 1989
neo 71665 Word!
Nowadays, with the ease and accuracy of CNC porting, I don't see the benefit of home porting stuff anymore.
American Thunder a cutter that knows what he is doing and has a bench can out do by 10x a CNC ported head.
@@bryanroupe8646 You would rather sit down, and hand port your heads, instead of simply sending them back to the company who made them for CNC porting? Or are you referring to extreme applications, such as top fuel?
Gaskets usually have much bigger port openings than the ports themselves. In this case do NOT gasket match. Instead, lay out the joint and PORT match.
unless you are using a flow bench it really is an educated guess as to where the best improvements will be made. some imperfections on an intake Are purposefully put in to add low pressure zone in the right place. velosity can be tricky. Very good general outline however. Look at how air reacts in bench flow u tube vids you will see what i mean.
smooth allows liquid fuel to flow into the chamber possibly getting on a plug tip and a misfire,,,,
you should look into dimple porting
GOOD SHIT
I bet a occasional aerosol seafoam treatment sprayed in to the intake in the engine on a direct injection system would keep the carbon deposits from getting really bad. I’ve seen a couple of videos on CZcams where this is done and it has made quite a bit a difference. One video even used a borescope to show how much carbon was removed from the back of an intake valve.
Jeff Stone I do my directed injected engine every oil change so far no issues
Good detail shown and explanation... Most cases where most obd2 systems control air fuel ratio adjustments automatically, this kind of improvement to the head is subtle in feeling the hp gain (slight increase in throttle response). The real gain and obvious difference is to redesign 3 things. 1) the intake manifold with variable runners are best because they offer economy driving and responsive throttle when needed since it redirects air flow more direct with less resistance(more air shorter period of time). 2) the power control module should hold the pulse of pintle of the injector open longer(more fuel). 3) intake ports and angle of intake valve in relation to piston should be reconfigured in order to maximize efficient combustion along with a cam with higher valve lift. Ive done your method of porting out the intake ports n polishing them out and purchased polished intake manifold and i was not so impressed with the results of my engine.
any one who has done porting knows where and how to port the head or intake
you learn from mitakes and gaines and some heads and intake only benifit from blending and port macthing and some lite polishing so if you dont know learn cause the out come could be much less hp with stock heads intake than you started with. but if you do your porting clean and clean and againe you dont want lose meatal in your rings and cylinders walls.and if you are thinking of porting look at the vavle it might be your problem that lip changes alot of flow it there to cause turblance so the mixture stay atomized.so do your home work before you grind.oh ya dont inhale the dust from grinding get a mask on or get sick from the dust the big Canser.
Question, what if it’s an older car that used indirect injection? Would porting and polishing not have a benefit in that case?
How about turbo direct injection engine? Is it any difference with non turbo? In terms of efficiency etc..
Its good to see young guys having a go and learning and you have to be commended for that. But i do think you may need a couple of thousand hours in front of a flow bench and the same on the dyno. Some of the things you talk about are correct but there is a lot that is not,and theory is great but in the real world of cylinder head porting and testing it is proven wrong! Cylinder heads are funny things and the physics involved needs to be understood correctly, but if i can offer you some advice it would be to do some reading up on boundary layer effect and airflow dynamics. Also ports are great but most of your gains will be found in valve seat profiles. Anyway keep going with it and keep learing but just don't get set in your ideas and thoughts as applying real world testing and science my change your mind.
Don't sand blast or glass bead ohc heads! There is a chance you won't be able to get some out of the oil galleys. Find someone with a soda blaster
You want turbulent air in the intake runner to make the fuel and air mix better but inside the combustion chamber you want the air flow smoothed out to aid in exhaust gasses being expelled. You can make the intake port too large before it hits the intake hole on the cylinder head which will cause a drop in incoming air velocity so you need a restriction from the intake runner to the valve. You don't want to loose too much velocity.
I Cerakote those bad boys including valves, piston etc
what is your say about putting dimple finish in intake ports just like on a golf ball?
99% of porters are doing it wrong. Do not ever use a pneumatic grinder unless you like oatmeal. Take intakes up to 80 grit polish the exhaust to whatever. Watch the short side radius. Use a stone on the ssr if your not Mondello level porter. Do not chase casting seems. Raise the roof , and just clean the floor. Pull your radius and straighten up walls. CNC is for heads that are popular sbc , honda. Even then a porter should clean up cnc work with a stone. For the home gamers. Get yourself a dimmer switch and plug in a metal box with extention cord and a Makita straight grinder. The dimmer will control your speed. To keep your carbide clean USED motor oil is best. No need for fancy cutting oil.
Polish combustion chamber and exhaust on carb'd applications. Fuel needs to stay in suspension. With polished ports, fuel sticks to smooth surfaces, coming out of suspension and pudding in the port. Not what you want on a carb'd app. If you're injecting into the port, anything above the injection point can be polished also, to put it simply.
There are a lot of people telling complitly different stuff about enlarging,polishing etc. I think enlarging ist just nessesary if you go up with power in general like with a Turbocharger. What about an N/A Engine? I have seen a Video where they test the flow of a Cylinderhead with 4 Different ports.
Original,Enlarge,Polish and Golfballport. The difference of the best one(Golfball) is just about ~5% thats not alot. Is there really a Power difference in the hole powercurve for a NA engine like my 1.6 Honds crx?
Sooo a rough finish flows much better were it's wet in the intake so polish upstream from the injectors but emery cloth 60-80 grit for the wet. Reason is fuel sticks to the walls and hurts flow and fueling. You could polish the combustion chamber and exhaust port but these days I ceramic coat all that works better for less effort if you ask me. Have fun
Brill vid
Look at renault F4R and F5R (non direct and direct) and look at the mpg ratings and real mpg ratings on these 2 Ltr engines
May interest some peeps with regards theory and practise
Alex Rogowski elaborate.
Alex Rogowski expound please
Doesn't sanding down all those bumps on the intake contradict what you said about rough intakes being better?
Sanding down with a low grit like 60 grit will still leave imperfections encouraging fuel atomization so no it doesn’t really contradict what he said
4.6 2v is notorious for having horrible flow. You can see a 50-100hp from porting high end is CNC & a full job low end it just matching up.
Wait so on my jeep the fuel injectors are right at the head, so I need to port and polish the intake to get best results? I'm installing a 4.7l stroker and I planned on doing the throttle body and intake
What about dimpling?
I want to see the Mimi running
I am really excited to see the Mimi running
How much horsepower gain would you get doing this?
Damn, I guess anyone can be a internet engine builder and internet engine machinist nowadays...
I want actual numbers produced by sensors from a thing called technology. I don't want theories.
dont talk
👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼👏🏼nice lecture 👍
Ok late to the party but how about vapour blasting ports. A middle ground finish. Anyone got any thoughts on that.
There's nothing wrong with mirror finish in the intake port on a mpfi system. Your argument is more relevant to throttle body injection or carb systems where fuel is introduced at the manifold inlet and needs to stay atomized. In a mpfi system the much higher air velocity at the moment of fuel introduction combined with the short travel distance makes it a negligible benefit in atomization leaving some roughness to runner. You'll benefit more by mirror finishing and flowing more air in. The smooth port in modern plastic manifolds is a perfect example of this
Without the use of a flow bench, there isn't a way to test what I'm saying vs. what you're saying. By removing the nasty castings, I think we can both agree that is where the most amount of power will be extracted from. By going the extra step to go for a mirror polish is negligible for both systems.
milanmastracci actually i think you'd be fairly surprised by the difference in flow turbulence can cause, especially when there's really no need for it
Granted most of that will be seen at higher rpm but on smaller higher revving engines you can certainly benefit
generally mirror finish the exhaust port purely to prevent carbon build up, you never polish the intake ports EVER even on direct injection. The mirror finish actually slows airflow down. You leave the intake ports rough like about what 80 grit sandpaper would leave for a finish. The rough surface traps air and allows the intake air to flow with less resistance due to the air on air contact instead of the air on port wall contact.
userpike nice explanation.
You can most definitely port a composite intake. But I only recommend it if your head ports are larger than the intake ports
You and I are both trying to squeeze every bit of horse power out of these n14’s . You need to talk to Ray from way motor works . He has been pushing these engines for years. Get the street cams and exhaust manifold ... a true 20-30 whp gain
What about dimpling the intake ports and manifold? There's mixed opinions about it, but not really a solid yes or no as to whether it improves performance.
Does nothing
How about dimple port?