I5 Head Porting and Polish

[DeWitt Harrison]

On Fri, 9 Nov 2001 06:52:29 -0800 (PST),
   james accordino <ssgacc at yahoo.com> wrote:

> 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.  [ ... ]

Much of the porting literature I've seen recommends
a precise match only on the intake side. The ports
in the exhaust manifold are often larger than their
mates in the head in order to create anti-flow reversion
steps. One good reference off the top of my head is
"Practical Gas Flow" by John Dalton, ISBN 1 899870 08 3.
This is an easy to read paperback which, in addition to
much illuminating discussion about flow in heads, shows
you how to make a dirt cheap flow bench from garage
junk which gives highly reproducible results.

DeWitt Harrison
88 5kcstq