dennis blackstone

for the experts on engine rebuilding , i started polishing the ports but i went a little to much were the arrow is in the pick ,is that iron still usable ,and do you get any power just polishing the ports ,its my first rebuild i thought i would give it a shot ,thanks fellas

Aaron Cake

iTrader: (1)

It's really hard to tell from the picture. If it doesn't cut into the oil ring path based on the wear marks on the housing, it's usable.

dennis blackstone

thanks arron by me polishing the roughness out of the ports is there any noticable power increase

Aaron Cake

iTrader: (1)

No. In fact it will hurt flow.

patman

iTrader: (3)

depends what you consider noticable.... you will gain maybe 2 or 3 hp, depending what your other mods are. my philosophy is, if i do every little easy thing like that that gets me 3 hp, at the end I end up with 30 extra ponies, so polish your heart out!

as far as the port...i cant tell real well in the pic, btu it looks kinda scary to me...like aaron said, if it crosses the wear line from the side seal, its not a good idea to use it.

patman

iTrader: (3)

based on what?

btw, why can i only see one post at a time right now?

dennis blackstone

well i stopped polishing when i did that so its still stock looking ill get better pics my set up is a 3rd gen fuel pump bnr stage 2 turbo upgrade isuzu npr front mount a wolf 3d 720 /1000 for fuel im rebuilding the oil metering lines and the oil cooler lines so im trying to set this motor up the best i can not for dragging but forn my own enjoyment ,atempting this engine build will be a first for me but i will learn by my mistake ,and keep everyone updated on my progress ,has anyone pics of there engine rebuild and port polishing to help me out thanks guys and gals

scrip7

iTrader: (6)

When it comes to porting, two of the most important considerations in making rotary power are intake velocity and port timing. When you make the intake ports too wide you lose velocity. Raising the top of the port and lowering the bottom changes port timing, and when done in just the right amount, you get noticeable changes in the powerband. There are quite a few threads on this if you search.

dennis blackstone

thanks scrip7 for the info but I was only polishing then ,just taking the roughness out of the ports is there any increase in power by doing this

Aaron Cake

iTrader: (1)

That's not entirely accurate.

Moving the port and towards the middle of the iron makes it close later.

Moving the bottom down really doesn't do anything but increase port volume.

Moving the port outwards towards the housing causes it to open sooner.

It's actually the top outside corner of the port that opens first.

patman

iTrader: (3)

aaron please elaborate on how polishing hurts flow?

thanks
pat

Aaron Cake

iTrader: (1)

Google "laminar flow" and you'll get the details.

gxl90rx7

iTrader: (1)

never heard of that before.. i suppose it is the same concept as dimples on golf *****, the air pockets reduce friction. Imperfections in the port passageways act the same way? So why is port polishing so hyped up if it is bad for flow??

fastrotaries

you can remove rough casting, and smooth the port out. But you can't "polish" it shiny. Bling doesn't really help here. If you don't want to change timing, look into the port from the side and widen up the mouth. You'll notice that a little more.

dennis blackstone

fastrotaries do you have any pics on this concept ive used the search but come up with porting pics all i was doing was smoothing out the roughness in the ports with a grinding stone know on the pic were the arrow is is that the danger area ,if so what actualy happens thanks guys

RETed

I hope this was a typo, and you missed the key word "up" in there.

Opening the port upward makes it close later.

Going toward the middle just gets you into trouble.


-Ted

dennis blackstone

retet thanks for the info i just was trying to get the roughness out and i went a little bit towards the middle is that iron toast

Aaron Cake

iTrader: (1)

Yes, I missed the word up. The funny thing is that I had to retype the sentence twice because my stupid wireless mouse freaked out and ended up highlighting half the text in the post and I thus I typed over it...

Up and towards the middle (referring to the upper edge of the port that points toward the trailing plug and not the edge closest to the eccentric hole) makes it close later.

fastrotaries

As a whole you'll want to stay away from going towards the eccentric shaft and directly down.

If you do your exhaust ports as well, you'll want to keep from going up.

What I meant was that If you look at the Iron from the side, the way the airstream would travel. Porting out some material, thus increasing volume. It'd be pointless to go crazy unless you were going to open up the intake manifold as well. For now I'd just try to port match it. If this is your first engine build I'd really keep it simple, and focus more on checking the clearances on the motor. Anyone can put together an engine, but that doesn't make you an engine builder. Just an assembler. Checking all the clearances is most of the work. Please take your time, you'll thank yourself later.

patman

iTrader: (3)

I doubt the flow at the intake port is very laminar regardless of surface finish, but just for the record, a rough surface is almost always bad for flow. if you have an aero reference, look up moody chart in the index. this describes the relationship between the relative roughness of a surface and the friction coefficent for a given reynolds number. Notice that the smoother the surface, the less frictional drag there is.

smoother surfaces have lower friction coefficients, so a polished surface will induce less drag, and a thinner boundary layer, hence better flow, especially in pipe flow situations.

dennis blackstone

thanks arron that made good sense I have a machine shop at my job so I will take your advice and check the clearances .one more question I have the 3 piece seals what do you guys use for you own rebuild and have you had long life with then, I'm using brAnd knew houseing what are your opinion on apex seals I read a few threads but I'd rather here from a 2oo7 point of veiw

scrip7

iTrader: (6)

For years I have read articles on port smoothness and the most common element in the discussions were to have the smoothest finish on the exhaust side of things, and a slightly rougher finish in a port or intake runner where fuel and air travels. It was explained to me that fuel droplets are more likely to "roll out" and separate (also referred to as "puddling" by many engine builders) on a highly polished intake runner. I polished the exhaust manifold and turbine housing on my tII to an absolute chrome-like finish and I port-matched my upper and lower intake and removed some casting flash, that's about it. I suppose a person could polish the UIM runners on a rotary and leave the LIM as-is and see some sort of improvement, who knows.

dennis blackstone

thanks scrip7

Alex Rodriguez

iTrader: (137)

POLISHING the whole port hurts flow because you need a little turbulance ,when its smooth the air doesnt all go in fast its more like shoved in

now polishing just the outer port will help with the seals or rotor not catching on a rough corner

Alex Rodriguez

iTrader: (137)

oh and you wont notice anything porting a stock port just leave it alone if you are not opening the port or streetporting it