I5 Head Porting and Polishing

[james accordino]

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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