I5 Head Porting and Polish

[james accordino]

Is this specific to turbo engines?  I'm speaking about
"flow reversion".  I seem to remember that the exhaust
gases exited in pulses and the key was to interleave
the pulses at the primary-secondary collection point
and also at the secondary-main exhaust collection
point.  Almost creates a suction.  This was why
primary and secondary dia. and lengths were so
important.  Also location and size of any crossover
pipe.  Again I'm not sure how the turbo effects this,
as I've got zero experience with custom exhausts on a
turbo motor.

Jim Accordino

--- DeWitt Harrison <six-rs at home.com> wrote:
> 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
>
>


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