Porting IDI heads - please quantify

[Smokey Eddy]

how much, and im looking for measurements here, can you port these IDI heads?
I did gasket match my 1.9 head but i want to go above and beyond. I was just using abbrasive bits on a dremel before but i bought a carbide bit yesterday to go crazy with.
How big can you make the ports and the runners inside the head?
Does anyone have or know of measurments?
I dont want to go into a water jacket and ruin the whole thing.
I recall seeing pictures of i think Aki-76's ported head and the ports looked massive (as well as glass like on the inside).


Also, I've added a semi-related poll. Please do not discuss the poll - just vote.
the reason i ask for no discussion is because it has been discussed before and some people get very passionate on what they think is correct. I just want to see what concensus comes out of the poll.
thanks.

[theman53]

Here is this.
http://www.vwdiesel.net/forum/index.php?topic=15782.0

The guy that did mine would probably tell you what to do if you called him. His name is John alder*I think* and it is air cooled engines plus in tiffin ohio. He said the exhaust is pretty good from the factory, but the intake is what needs help. He also told me it was more on the sides of the port and not as much on the top. I had mine done and it is about the same size as the gasket on the intake, but I got close to double the flow. He said it is all about velocity. Good Luck.

EDIT- air cooled engines plus also told me that most of the work was done in the bowl area. The ports can't be done too much as he has had some that leak coolant if he goes too far.

[Smokey Eddy]

ooooh okay
so i want to cut away until its almost flush with the valve seat. I see i see. Rounding off the valve guide would be a good idea too i bet.
ps. I already had the PDF.
I was speaking specifically on how big to go on the intake side of things. the "top" as you would call it. but i'll spend much more attention to the areas outlined in the pdf then.

[GEE-BEE]

I used extrude a hone on my head and my PD130

www.extrudehone.com

550.00 for the head

PD130 was less $$

They are both like a mirror

Liquid plasma polishing...

I did my intake manifold on my aircraft years ago and it idled very smooth, compared to before

GB

[Smokey Eddy]

thats a little too pricey for me GB
i think a polishing bit on my dremel will do fine.

[rallydiesel]

I have heard the opposite. Threads on tdiclub seem to say heavily porting the exhaust gives more of an advantage, especially with big turbos.

[Smokey Eddy]

I have heard the opposite. Threads on tdiclub seem to say heavily porting the exhaust gives more of an advantage, especially with big turbos.

I dont think he is saying not to port the exhaust side, just that the intake has different casting? perhaps because of the size difference in the valves? i dunno.

and i am talking about how some people say to leave the intakes rough to ... stir up the air going into the cylinder or some crap. but i think that's only a gas thing.

[burn_your_money]

and i am talking about how some people say to leave the intakes rough to ... stir up the air going into the cylinder or some crap. but i think that's only a gas thing.

That is my understanding of it. If you make a gasser's intake port mirror then there won't be enough turbulence to mix the fuel and air.

[Smokey Eddy]

and i am talking about how some people say to leave the intakes rough to ... stir up the air going into the cylinder or some crap. but i think that's only a gas thing.

That is my understanding of it. If you make a gasser's intake port mirror then there won't be enough turbulence to mix the fuel and air.

is such the case with diesels? i figured the air is going to be in there already and its all going to get excited as it compresses and gets hot to the point of combustion.

[8v-of-fury]

is such the case with diesels?

Shouldn't be as the fuel air mixture doesn't happen in the intake runner at all With the diesel it shouldn't matter of finish just how much and how quick you can get it in. A smooth finish (to me) should be able to more easily flow air then a rough bumpy surface that will cause turbulence and crossing waves of air.

[Smokey Eddy]

is such the case with diesels?

Shouldn't be as the fuel air mixture doesn't happen in the intake runner at all With the diesel it shouldn't matter of finish just how much and how quick you can get it in. A smooth finish (to me) should be able to more easily flow air then a rough bumpy surface that will cause turbulence and crossing waves of air.

my thinking as well.

[745 turbogreasel]

But the boundary layer of little vortexes coming off a rough surface may  do more for flow than a smooth part that isn't following an aerodynamically perfect path....
Id be more about flushing the intake guides than exhaust, the exhaust valve has a lot of heat to shed

[bugnut]

Look at the surface of a golf ball.  It is not smooth for a reason.  The dimples actually make it go farther than a smooth ball would.  I saw it once on mythbusters.  All my intakes are smoothed to about 80 grit to keep the turbulence up.  The exhaust on the other hand is smooth like glass, don't want the carbon to build up on the ports.  Also do not gasket match the exhaust port to manifold.  Keep the port on the head smaller than the exhaust manifold.  You can match the port to the gasket but make sure the manifold is bigger than the gasket.  This creates a low pressure and helps suck out the exhaust gas. 

[8v-of-fury]

Look at the surface of a golf ball.  It is not smooth for a reason.  The dimples actually make it go farther than a smooth ball would.  I saw it once on mythbusters.

AH YOUR RIGHT!! Where they took that Ford Taurus and put clay all over it and dimpled it, and did better numbers then without the 1500lbs of clay? I stand corrected. Ed leave some golf ball dimples in the intake

[RadoTD]

I've always wondered if rifling ports would help eliminate the boundary layer, or at least thin it out