Dave:
I would add a caveat here; It is not based on personal experience,
but
is based on what I have read in David Vizard's book "The theory and practice
of Cylinder Head Modification". This book specifically addresses the GT6 and
TR6 6-pot motor.
Vizard claims that the later ('wide port') 6s have an excellent
port design that if anything, is already too large. He recommends not
enlarging the ports at all.
The only changes to the ports he recommends is to blend the
short side radius in the valve pocket, and slightly enlarging the
valve pocket on the long side to create a slight venturi.
Vizard claims that the power gains to be had on the 6 are to
in reducing valve shrouding in the combustion chamber. He claims
that enlarging the ports on the later heads will reduce horsepower
because the velocity of the incoming air-fuel charge drops off
unacceptably. The early heads do not flow nearly as nicely, and
benefit from cleaning up the ports. 'Course the early heads had a
higher compression ratio, and so made more power despite their
flow limitations.
On the later heads, milling to raise the compression is the
single biggest pop for power you can get. So in order, on a later head
Vizard says to:
1. Raise the compression
2. Reduce valve shrouding
3. Blend/reshape the valve pocket
If you want to soup up your 6, this a great book. It has
some really nice drawings on how to reshape the chamber and valve pocket.
I recommend it.
Ciao,
Vance
P.S. The book can be ordered at www.amazon.co.uk. Best I can tell
the book is unobtainable in the US for a reasonable price.
---------------------------------------
The most likely way for the world to be destroyed, most experts agree, is
by accident. That's where we come in; we're computer professionals. We
cause accidents. - Nathaniel Borenstein
-----Original Message-----
From: TR6 Triumph [mailto:tr6_1969@hotmail.com]
Sent: Wednesday, April 30, 2003 7:57 PM
To: bereza@pobox.com; 6pack@autox.team.net
Subject: LIST of things to do when doing your head
Hi,
<snip>
1a. Port the head. Id est- grind the passageways that that more fual-and air
can travel to the head and can do so in a more streamlined way, hopefully
reducing the resistance to the flow. More fuel-air per second, more power
(also more heat).
<snip>
Sincerely,
Dave Herbert
1969 TR6 and nothing else
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