Ported head

[Anonymous]

Today I started to lift out the engine of one of my 16v´s and when I took of the manifold I saw it was grinded in the ports. Not so much but it was a nice surprise anyway Is it possible to see if it is bad or good work? I have no idea myself Ive been driving the car before and it feels fast, but not extraordinary.

Picture:
http://hem.bredband.net/thedagger/head.JPG

[Mandic]

Porting this head in a right way is according to some thrustworthy specialists a very hard task. It is a brillinat head as astandard.

So unless You do a flow test You can not know for sure. But if only ports have been slightly ported I doubt there were any gains to be expected. Modding valve seat and area where port ends is the key to gain power.

Cheers

Ziga

[Toddman]

As a rule you cannot tell the effectiveness of mild porting by eyesight as Ziga says a flow test is needed.

A lot of experienced engine builders will do some work on the ports even on a std rebuild to remove casting flash etc, some of these mi heads are very rough inside even though they are a great head they are still mass produced so a hand finish can help to smooth out the roughness.
These heads do have 3 angle seats from the factory but often they are barely visiable so a decent recut is often recomended.

IMHO if it has just been given a general clean up and smoothing out then it should be good but as already mentioned if too much has been done by an amatuer chances are it will not be so good.

Chers
Luke

[Anonymous]

Thanks guys
If I have time ill take the head to a specialist i know and let him at least have a look at it. He have flowbench too but at this time I cant afford that.

Ill try to lift out the engine this evening so I can see the exhaust ports too

[Mandic]

What ever You do, don't try to improve exhaust flow. Visit pumaracing site at: www.pumaracing.co.uk and have a look...

Cheers

Ziga

[jan]

The idea behind head porting a street-driven engine is to enhance flow velocity without exsessively enlarging port volume. A very experienced tuner may get positive results without a flow bench, especially if modifications are done primarily in the valve-pocket area. However, except the real nerds on a specific head, nobody can glimpse twice and exactly evaluate what the grinder has done. Being a fact that many heads require less port volume to get the ideal balance between flow and velocity.... you really don't know what's done until the timeslip tells the thruth.

[Mandic]

Well mi16 ports are big enought from starters, maybe a bit too big, so enlarging them is a step back imo. Like Jan says, one needs to engance flow velocity without enlarging port volume.

Mi16 has 9.2mm of lift and You really need bigger lift cam to make use of all that flow potential, like I said before, better focus on lower part of the port. And don't polish inlet ports.

Cheers

Ziga

[Toddman]

Why not polish the inlet ports

From my years of tuning I was under the impression that the only issue with highly polished inlet ports was the formation of fuel droplets from the air/fuel mixture but a general clean and polish is good for flow, I mean polish with fine grit rathe rthan a mirror polish with paste etc.

Cheers
Luke

[Mandic]

Yes, I'm referring to mirror polish, as mixture needs to mix well, fuel needs to vapourise, and like You said fuel drops are forming, ...

I know pumaracing talked about this sometime ago, must find his post.

Take a look at this port. Cosworth build Impreza Type 25 engine.



Cheers

Ziga