I5 Head Porting and Polishing

[alan pritchard]

imho you dont match the exhaust ports, infact i understand it is better for
the em to interfere with the exhaust gasses slightly, either at the top, or
bottom, either way effects power delivery slightly, cant remember how, but
thats what the book told me!!
----- Original Message -----
From: "james accordino" <ssgacc at yahoo.com>
To: "Iain Atkinson" <iain.atkinson at tesco.net>
Cc: "audi list" <quattro at audifans.com>
Sent: Friday, November 09, 2001 2:52 PM
Subject: Re: I5 Head Porting and Polishing


> IMHE the biggest gains to be had occur when you match
> the ports.  Port matching refers to equalizing the
> size of the port exits to the gasket.  When you match
> both manifolds and the head ports(usually to the
> gasket as this makes a convenient pattern) you
> eliminate any ridges or lips that would disturb or
> restrict airflow.  Other than that, I would limit the
> porting to cleaning any casting flash in the runners
> and some SLIGHT rounding/smoothing of the bowls
> directly under the valves.  The LAST thing you want to
> do is start hogging out material from the runners as
> you can get "dropout" when reduced velocity allows
> fuel to condense.  Again, my limited experience showed
> me that you don't want mirror smooth runners.  Rather
> some fine texture as from a medium grit stone.  If I'm
> way off, I'm sure someone else will post, but that's
> what I learned 20 yrs. ago working on small block
> Chebbies.  I don't think things have changed that
> much.  Good luck.
>
> Jim Accordino
>
> --- Iain Atkinson <iain.atkinson at tesco.net> wrote:
> > Hi all,
> >
> > i am going to start rebuilding one of the I5 heads i
> > have lying round and
> > need some adice pleae on how to port and polish. As
> > i have never done this
> > before i need to know what tools i need and how to
> > do it. I have the Dremel
> > and decent power drill but don't know what type of
> > grinding stones to buy,
> > and of course where to remove metal and where not
> > too.
> >
> > On a slightly different subject, i also plan to
> > install larger valves, what
> > size should i go to??? The engine is a 2226cc KV
> > engine (out of a UK Coupe
> > Quattro). Am i biting off more than i chew???
> >
> >
> >
> > TIA
> >
> >
> > Iain
> >
>
>
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