Don:
While what you are suggesting can't really hurt, I doubt that it
will make any difference unless you have already extensively reworked
your head. The reason is that the major restriction to flow is the
valve, not a small mismatch between the exhaust port and the header
tube.
If you have radiused your exhaust valve margins, done a 3 angle
valve job, pocket ported the head, and installed some sort of high
performance valve with cut down valve stems, etc. then I think you
*MIGHT* see a difference in flow by matching your headers to the head.
Headers generate power by virtue of the inertia contained in a
moving column of gas. That is going to happen best with a tube that is
long and narrow for a street motor. This will not be affected by the
mismatch that you are describing. Also, remember that the exhaust gas
pressure is high, and so in general flow is less affected by turbulence
than is the intake side of the motor.
Power in general is locked up in the head, and in particular the
power is locked up in the vicinity of the valve because that is THE
single most significant flow restriction. Spend your time, energy and
money on detailing the valve and valve pocket. That will generate the
best returns.
If you are at risk of affecting the weld integrity of the
header, don't mess with it. If not, then there is no harm in doing what
you are describing.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Don Malling
Sent: Saturday, November 13, 2004 6:00 AM
To: 6-Pack; triumphs@autox.team.net
Subject: Port matching and Falcon Group 44 headers
The round tubes on the Falcon Group 44 SS headers are welded to a head
mounting flange. The head mounting flange has rectangular ports which
appear to match the exhaust ports in the head. My plan is to port match
these rectangular flange ports with the head ports.
The question...
I've noticed that the edges of the round pipes infringe on the corners
of the rectangular flange ports. That is to say, the diameter of the
pipes is slightly smaller than the diagonal measure of the rectangular
flange ports. Based on the size/thickness of the weld that attaches the
pipes to the flange, and which is on the external side of the pipes, it
would appear that I could safely file away this small portion of the
round pipe that infringes on the corners of the rectangular flange
ports. This is a small infringement, but none-the-less, in the very
corners, the weld material is visible, so I would have filed through the
thickness of the pipe and would be filing into the weld at that point.
Should I do this or am I worried about nothing? That is, will doing this
provide any noticeable flow improvement for a street engine? It would
seem to me that even small obstructions would/could lead to a
significant amount of turbulence, and that it should be done.
Thanks,
Don Malling
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