Flowing the head is a tuning modification to a standard cylinder
head, inlet and exhaust system. It is usually done with a reduction
of the cylinder head thickness to increade compression and hence
(usually!) power output.
Generally in the 30s and 40s it was accepted that - broadly -
thinning the head alone was stage one tuning, After that
flowing the head and maybe bigger carbs was stage 2, then more
off the head stage 3 and stage 4 was back to a thicker head, but
flowed, and a supercharger to regulate compression pressures.
(Those with much money and a friend to take them home
would have the supercharger AND the high compression head!)
Basically the standard head from most cars is just cast for
convienience and the minimul work is done to it to make it work -
Valve seats cut - mamifolf faces machined and a bit of a tidy
up of rough edges.
This means that there are sharpish edges and corners, and
rough surfaces on the inlet and exhaust ports and the
combustion space that cause disturbance to the incoming
fuel / air mix and outgoing exhaust gases, rather than there
being a smooth fast flow.
To make a well flowed head then the inlet and exhaust ports are
matched to the head faces so any overlapping bits are eliminated,
the inlet and outlet ports are smoothed off and sharp edges and
corners smoothed out as much as possible to gife smooth flow
and regular section, the cylinder combustion space is polished
and any sharp pionts removed, and in sone cases the shape is
altered to promote swirling of the incoming fuel and outgoing
exhaust to give greater gas flow rates. The most visable result
can be the replacement of the original exhaust manifold with an
"Extractor" manifold that takes gases smoothley out of the engine
and away without hitting a bunch of right angles in the first 6 inches.
This can be taken too far though as some back pressure is
required by many engines and tuning the length of the exhaust
pipe to provide this through resonance is a genuine Black Art
from the depths.
Theres a lot more to it but thats the basics.
Regards
Clive
Oxford UK
=================================================
----- Original Message -----
From: <Locktc7440@aol.com>
To: <mg-tabc@yahoogroups.com>; <wargs@Mac.com>
Cc: <mg-t@autox.team.net>
Sent: Sunday, April 28, 2002 12:17 AM
Subject: [mg-tabc] Flowing the head....????
> This is for all of the engineering types out there as well as engine
> builders.
> I was having a dicussion with a friend a few days ago and the term
"Flowing
> the Head" came up. I have heard it before and assume it has something to
do
> with intake and exhaust gasses. What exactly is this procedure and how is
it
> accomplished? Please excuse those of us that are not up to date with such
> terms and procedures....
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
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