djmickyg

here is a pic of the intake manifold im porting out..
i've only done a primary and second port on one side sofar (right side if u cant tell)



to all the people that have done this b4 does, have i got a lil overboard on the primary port? or is that size alright? it's about 30mm in diamiter (1 1/4 inch)

the 2 lil holes ive circled in red are used for that pumpy thing on the side of the manifold which im not using. so can i thread tap them and put a lil grub in then to stop anything geting stuck in em?

and thats my few questions..
cant wait till i finish the other side, but it on the car and see if i've made it better, or fuked it up..

djmickyg

here is 2 good pics to show the difference between the 2 primary ports.

BEFOR

AFTER (befor i polished it up 10x better with a fine grit paper.)

SoRRoW

On the top ports,put your carb on top of it and open the butterfly and see how much room you got,I hope you didnt go bigger than the butterflys on the carb

On your housing side,put your intake gasket up to it,Dont make it the same as the holes in the gasket.leave soem room,

Dont polish out the runners on carb set up people like to keep them rough for the fuel,in injected set ups.people polish the **** out tof them

djmickyg

the primaries are made to the same size as the butterflies in the carb (i better check that agian, i might have gone die grinder happy.

the seconds i didnt make any larger, i just cleaned up the first turn,there was alot of bumps and i took off that nobby bit (circled in yellow)

the ports that go up agianst the engine i didnt make any larger either, i just gave em a polishing..

Edit : forgot to ask, why shouldnt it be polished for a carb setup?? that doesnt make sence to me

SoRRoW

Yeah the yellow circle I ported that out also and made it round..

Polsihing otu the runners on a carb set up,
I heard they leave it rough so the fuel can trickle down and give it time to (anotomize?)

Can someone post to give this theory?

Cloud

I'm not a porting expert, but there is a point to leaving the surface with some sort of texture. A polished surface can allow un-atomized fuel to trickle into the combustion umm...chambers (I'm new to rotories, if you don't like my termology...so what) and liquid fuel doesn't burn. The friction losses from a rough surface are minimal due to boundary layer aerodynamics, from what I understand.

It's like this - air travels slower along the surface. Check out your hood when it's raining outside and you're going 70mph. You can see the raindrops traveling upwards on the hood slowly, nowhere near 70mph.

Sorry if this doesn't make any sense, I just woke up. The intake porting is looking pretty nice. If you want some "real" advice, do some google research for intake and head porting on carbed piston motors. There's tons of it out there.

exodus82

would porting the intake like that actually give more HP. It seems like a good idea to me.

REVHED

Polishing the runners tends to make the airflow laminar which can allow the fuel to fuel out of suspension. Keeping the surface somewhat rough provides a bit of turbulence which helps atomise the fuel properly.

SoRRoW

If the port hoels ae not to big,just use a barrel ander in there,I use one on my dremel

PaulFitzwarryne

Congratulations to all who posted on this thread. Its what a good thread should be. A concise question and specific helpful advice. Its what the forum should be all about.

1st to 3rd

To get somewhat technical: Velocity at the surface is always zero. If the flow is laminar the velocity will increase the further away from the surface. Mapping the velocities vs. distance from the surface will result in a parabola (obviously decreasing as you pass midpoint). Many factors will change the shape of the parabola including surface roughness, but it will always remain parabolic.
Flow through any intake is far from laminar. It's a question of how turbulent it is. Turbulence is a good thing when atomizing fuel, but sudden changes in velocity are not. As the air/fuel mixture moves down the intake and makes turns velocities change dramatically which can cause fuel to fall out of the air and liquefy. Liquid gas does not burn, the vapors do. That is why it's not a good idea to **** with the bends too much as it can cause problems if you don't know what you are doing. Intuition tells ya to clean up the short side. See, around the outside of the bend the air must increase velocity. The short side slows down. Sometimes "flying off the surface"- separating from the wall and causing a vacuum. This can lead to reversion - the air actually flowing back up the intake... sorry if this didn't make sense - I'm too tired to think about fluid dynamics.

Now, back to reality. You went a bit wild with the grinder. Roughen the surfaces back up. I'm not sure of your combination, but on a tame combo you don't want to enlarge the passages much. Just remove the bumps and flashing. When you remove the shutter valve, do not attempt to open up the rest of the runner and the other to that size. Rather, close it up a little with some JB weld - or whatever you prefer.
I spent hours and several different variations of manifold porting when I had a 1st gen. Never did get it quite right. What I settled on was similar to what you have now only with smaller primaries. Good luck and share the results!

djmickyg

thats the plan..
i'm mainly looking for more bottom end power so thats why i've opened my primaries alot and havent really done much to the secondaries..

thanks for the info guys! .. i was really likeing my polish port, spent hours tring to work out the best way to polish it, and now im gona have to ruffen it all up again lucky i know this now and not after i put it in..

if all goes well i will proble try it out on the w/e. ive just to the one primary port to do. lets just hope my POS fuel pump will hold up..

Cloud

A few points:

1 to 3 (may i call you 123? is that cool? hehe) - good points. you tried a bit harder than i did, nice job.

DjMickyG:

1. Don't plan on gaining any "bottom end power" by increasing the effective plenum volume. Had you smoothed out the curves (properly and efficiently) and DECREASED the size of the "tubes" or runners, you may have increased your low end. By increasing the cross section and thus, decreasing velocity, you won't see a gain in the "low end" IMO.

2. Many head porters I know stick with ~60 grit on the intake, which is purdy dang rough. Sucks that you spent all that time making it so smooth! Surfaces that smooth only belong in the exhaust!

3. I wouldn't think you would really feel the power difference from the porting (on a stockport motor) - depending on the quality, you may get 5-7 HP max IMO. But considering the price (close to free, right) 5 hp would be sweet.

My brother has a few extra intakes laying around. I may do em up a bit and see what I can get out of 'em. Of course, hopefully they will flow enough to justify some carb mods...

Cloud

Some examples of how "unsmooth" you may want to stick with: (ignore those valve things!!)


I'll find more later. The woman is calling me to bed, and she can be umm....convincing.

djmickyg

i've just "unsmoothed" mine, by running the stone grinder back down em.. i think its done the trick

now i justa go get another stone. all mine have worn out the other primary hole is smaller..

is there a too ruff limit, or go as ruff as posable?

Edit: yeah it was basicly free, i had the intake just sitting there from my old engine and it wasnt ever gona be used for anything, so i thought why not, and looking inside the ports i notices that the top is wide but it very qucikly tapers off to a much smaller hole. if it works i'll be a happy man, if not i'll put the old one back on and pretened i never attempted this

PaulFitzwarryne

Cloud- 5-7hp gain from the porting is a little low comparedwith the usual claims. What evidence do you have?

ioTus

iTrader: (5)

Hey i assume this is for 12a carbed engines.

How about my GSL-SE 6 port 13b intake?

How would i go about porting/polishing that? Any writeups i could reference?

Cloud

Paul, I see you're my neighbor, cool. Porting the intake will produce various power increases, depending on the rest of the combination. You can only flow as much air as your smallest restriction (err...biggest restriction, smallest hole) USUALLY (barring venturi effect, etc.). So, on a stock port motor, you are still very restricted.

I am unfamiliar with DJ's combo (shoulda asked, oops), but am assuming it is a stock port motor. If he has a header and exhaust, and some way to tune the carby, he could in fact get lucky and make 10 extra hp. Or, if he has a stock exhaust and carby, and accidently screws the airflow through the runners causing reversion and other nasty things 123 discussed, he could lose power through the entire curve!

In ending, it's pretty pretentious of me to try to guess gains w/o solid specs of said set-up - but at least I entered in icky alliteration!





(First post of the AM never makes sense, roll with it )

djmickyg

well i put the new intake in today. all went alright...

i think its still to early to say if it's made any difference but it did seem a little bit better, but i didnt get to take it on much of a drive..

the only problem is the idle is on 1000 and when i went to ajust the idle screw it didnt drop the idle it just gave it a more lump idle the more i turned it? so i turned it too where it was smooth and its still around 1000 (dam how many times did i say idle)