check this out. dude called motoman has this site and i was wondering what everyone else who cared to look thought. the views here contradict ALOT of what every engine builders thinks and what we as tuners\builders have been sold. this is mostly about motorcycles but all engines 4stroke work basically the same. just big pumps if you will. anyway check it out and see what you think. the site is mototuneusa.com come back here and let us know what you determine.

 

This is very old news.

 

Pretty much every engine builder on this site goes by that method, which motoman did not invent. I don't know where you get your information that it contradicts what every engine builder thinks. I think YOU had just never heard of it before & assumed others hadn't. Old news, though.

 

i never said he invented how to break an engine in. im sure there are some on this forum that have never heard of this before. but if you can speak for everyone then maybe you got all the answers. besides i was most shocked not by how he breaks an engine in because thats how me and my brothers did it 20yrs ago did it. but his thoughts on port and polish being a waste of time and money and how valve ports and valves themselves on some engines are too large to begin with. did you happen to read his artical on this? ive noticed not everyone has done without ported and polished heads being in their build desciption. maybe not everyone uses his info or this same tech. so the point being what did YOU think?

 

You're generalizing his writings. On some engines, bike engines, he found gains in shrinking the ports. A lot of time, its not even the shrinking of the ports that improves the performance, its just the altering of the port shapes.

If porting & polishing is such a waste of time, why does EVERY engine respond to increased airflow? Why are NASCAR, Pro Stock % F1 constantly revising their port designs to find more power? My thoughts on his article regarding cylinder heads: much ado about nothing.

 

dont think he shrunk'em more like removed dead airspace to increase velosity and ribbed port wall to cause turbulance to more effectivly mix fuel and air before combustion. others on his site have done same to car engines and seen dyno proven gains. pro engine builders go by calculations to build an engine not cause everyone said get a port and polish. how much can just a port and polish alone add? think id rather be port matched till i had proper piston size and cams to accomadate added air from a port job. true every engine responds to inceased air flow motors are air pumps but not every motor is a stocker with a port and polish why do port and polish if nothing else? f1 and nascar dont use factory heads they forge their own to their set ups specs so their excluded ive never made my own cam,crank,head or pistons have you? velosity is just as important as flow.

 

How do you increase mean velocity in a port without shrinking it? He used epoxy and shrunk them, read the article. And here we are back to the turbulance argument again. Show me how in port turbulance leads to increased power. Ill tell you what it leads to, decreased emissions and reduced top end ouput. You want the airstream is in the port to be as laminar as possible for peak HP.

F1 & Nascar CAST their own heads than run different port designs on CNC machines, then test each config. For airflow/power output. That is their version of "porting" & if you have the budget to do it, its puts hand porting to shame.

Velocity is NOT just as important as flow, not on a racing engine. It is important but not AS important. If I have to sacrifice a little bit of airspeed for a 10cfm gain, I will. Especially if its a 4 valve head. I am just telling you from years of experience what I have found that works.

 

its easy to increase velocity in a port without shrinking it. turbos, chargers and nitrous do this. the idea behind his theory is that most head ports are already too big in his examples its shown valve size vs port size w some math and there you go. im not arguing anything with anyone so dont get mad or roll your eyes when somone elses ideas conflict with what you were taught or learned you aint gotta keep postin, im not forcin ya. all i know is if you keep doin what you always have youll always get what you always got. always think outside what you know. on velocity thats what keeps air goin in even when the pistons startin to come up before intake valves close. losing some velocity from a correctly matched head job is fine but youll probably see gains in all aspects if its correct, its just as important, without it what would you have? instead of losin bottom end and gaining tons of top id rather have a gain ALL the way across. but i spend my time at road course and autocross. leave dragstrip to the straightaway set up. but i have raced a few drag strip guys with head work and they got smoked. and i have been smoked by guys with the right matched parts and proper head work for their set up. shrinkin the port is one way to look at it, maybe the not changin my mind way but if it was too big already i think he matched it to what was needed espcially since there was a gain all the way across the power band. besides more air needs more fuel thats why 2 barrel carbs have 2 jets and 4 barrel carbs got 4 and the jets that supply the fuel can be swapped to the correct size for your set up. ever see ported polished head with over sized valves on stock injectors? bet its a lean burner.. what about cam lift or duration? deck height? compression ratio? stroke? bore? is this all figured in your experiance? and why is turbulance an argument to ya why is that bad in your eyes?

 

Turbo/superchargers increase air density, not airspeed.

A wise man once said that there is no such thing as too big of a port, only too small of an engine. lol

 

What you think that blowoff valve is lettin off air density? ha ha ha

 

it lets off back pressure.

 

This response pretty much sums up your lack of understanding of this subject. You clearly do not understand the difference between velocity, density/mass, volume and pressure.

 

besides turbo or charger or forced induction of any kind if you give a cylinder more displacement or volume the air volocity has nothing to do but move faster through the same port as before when stock bore was there, even at same engine rpm the larger cylinder would be pulling more air through the same port as before. it would have to increase velocity. agree?

 

hey "never-lifts", just listen to what these guys are sayin and you might learn something about physics and engine performance that you didnt understand before. if Ive learned anything on this forum already its that nobody knows it all, but some people know alot and you learn alot more if you listen and ask questions instead of arguing. Not trying to be a suck-up, Im just tired of people arguing when they dont know what they are talking about

 

will you help me understand? how does it work? does a turbo not heat up air and pressurize it towards the intake as it passes through it? does a intercooler not cool the air back down? is a turbo not forced induction? what does fore induction mean? does a turba not increase air velocity? how does just the turbo increase density? i hate when people point out what i say is wrong but dont tell me what they think, they are all like just clearly your wrong but im not tellin you what is right or what i think. intercoolers increase density from what you told me last time. and you also told me blowoff valves release the air thats prssurized thats movin up to my closed throttle plate. no wait you didnt tell me nothin nevermind.. beside gettin off track here this aint talkin bout no displacement replacers this is head work talk go to a forced induction thread and argue there

 

wow didnt know i was offending so many. guess my experiance has got me nowhere. maybe i am stupid. maybe i havent got enough posts to know anything.. maybe my mechanical engineering degree is a fake. maybe i shouldnt have been workin on cars since i was 3 with my big bros. im 33 now by the way. wow thanks for the voice of advice. really im not tryin to argue just everyone is tellin me im wrong but none tell me what is fact i was gettin somewhere with that combustion contraption fellow i like him.

 

apparently you must have missed a few sessions.

 

i didnt say it!

 

Its all well & good saying you want to gain power all across the board, but that's rarely accomplished with parts/porting testing in NA applications.

And I said in-port turbulance is bad for peak HP because it simply is. Any turbulance is going to detract
from mass flow because its robbing the incoming airstream of energy.

And no, a larger bore won't substantially affect airspeed in the port. the pressure drop in the cylinder is what affects velocity. Going with a larger bore doesn't guaruntee you a larger pressure drop, that's mainly influenced by stroke length/rod legnth/cam timing. But now we're talking instantaneous velocity whereas I have been speaking about mean port velocity the entire time.

"If you keep doing what you've always done, you always get what you've always got"? Well, I am always open to new ideas if they have merit, but I am happy with what I know now, because it works. If I find something that works better, of course ill incorporate it. But when its something that's counterintuitive, such as inducing in-port turbulance for power output, I won't shy away from breaking out the bullshit flag.

Oh, and lastly, the more airspeed a port has, the quicker it will go into choke.

 

totally correct cc its okay if i call you that right combustion contraption? stroke and rod lenth cam timing and lift are ways to change instantanious but not the MEAN velocity. had to see what i was dealin with here. dont know about that last part bout air speed maybe you mean how much the port its self produces not how much is in it.. i think i totally understand you.you are the only one who hasnt tried to say your crazy without statin what you know and i respect that i damn well like it. everone else is most likely forum junkies.or read a few magazines and is boss dawg. thats not what 5k post guy said if you will. hope we can talk more about things. do you only mess with hondas? currently building a 408 chevy. may have my eg for sale dart block and all.

 

Um...yes. Since the air density in the charge pipe is higher than the ambient air, it is releasing the air density (aka pressure).

 

My business deals with 95% honda stuff, but I do a lot of work with other shops that contract out work to me. So I have a hand in pretty much every type of cylinder head out there. stock chevy & ford, dodge, AFR, brodix, trick flow, edelbrock, etc.etc.

I have also done a lot of vintage repair work, for heads that you can't buy anymore. I have even had a hand in repairing a 1930's (can't remember the exact model year) Model A head. A lot of vintage Jaguar, Ferrari & Porsche stuff as well.

 

Where is the power in a B series? The head! And the PR3 has great flow for a factory head but there is always room for improvement. Shape has a lot to do with it also because of turbulence which is bad. This is where a flow bench is extremely helpful. You can see the problem spots and fix them which sometimes involves adding material but bigger ports, better shaping, more flow which usually results in more power. Now I have seen port work gone bad where they just made them real big and ended up losing power. I'm not sure if thats directly related to velocity or because of bad shaping, maybe both. Its a science lol. Ive done port cleanups before and thats about it. I read as much as I could on how to port a head but it really is best left to the pros. Hence why I just did a casting cleanup rather than removing material and shaping them differently.

 

the head is where the power is in every engine......you just have to have a bottom end that supports it.

 

the whole point i was getting at with this topic is bigger isnt better. in the past manufactuers have revised past year model cars and gotten more power from smaller valves and smaller ports on the same engine from previous year models. ive seen this at the dealership shop i wrenched at when the wrong parts were ordered. always look at the part numbers guys if you work in the parts dept.. i wasnt tryin to argue with anyone or claim i know all. hell these aint even my words. when i first seen this years ago i was blown away that someone would pour jb weld into a intake port. wtf is he thinkin? but after you think about what was going on it make since if the ports too big take away whats not needed to gain that 5hp. not sayin every motor is this way fortunatly honda makes the best looking and in my eyes does the most to get all they can from a small displacement engine given the restictions and its all in the valvetrain and design of the head so why go mess with it unless you need to lose weight in valvetrain or building i high reving drag car? i can see springs and cams for your daily but really? just cant see why some wanna gouge it out till its thin as paper on a stock stroke and piston.