Robert:
Interesting question.
I would submit that your case is different from what has been
offered up on the list. Vizard's injunction against enlarging the
ports on the TR6 is a bit different than what you did (I think?).
Your exhaust manifold was occluding the exhaust ports,
so it sounds like you eliminated a mis match on the exhaust side
(only). Do I understand that correctly? And it also seems that
you resolved the problem not be enlarging the port, but by
clearancing the exhaust manifold. This is an excellent idea, IMHO.
I will definitely be checking my exhaust manifold tonight when I
get home. =:-)
Vizard says that the TR6 ports are slightly too large, so
don't enlarge them. This is not an injunction against removing
a mismatch. In any event, the intake port on the later TR6 head
already matches the intake gasket, so there is nothing to be
done with regards to gasket matching.
The exhaust port is another matter. It is slightly smaller
than the gasket opening, so one might be tempted to do a gasket
match on it. It is interesting that Vizard does not show any
significant metal removal on his ex. port template for the later
TR6 head (In either "Theory and Practice of Cylinder Head
Modification" or "Tuning Standard Triumphs over 1300cc").
Flow numbers would of course show that enlarging port
increases flow, but it does not tell anything about "wet flow",
which is where Vizard claims you get in trouble with too large an
intake port.
Horsepower numbers are the ones that will tell the tale. Flow
numbers will only tell you about dry flow.
So, anyone got any horsepower numbers, or know where we
can get some? Kastner's book has some nice ones, but it doesn't
address porting issues explicitly.
Vance
------------------------------
1974 Mimosa Yellow Triumph TR6
Cogito Ergo Zoom
(I think, therefore I go fast)
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Robert M. Lang
Sent: Monday, March 01, 2004 9:22 AM
To: 6pack@autox.team.net
Subject: Re: Port Matching
Hi List,
Okay - there's been a couple of go-arounds on the list about whether to
port match or not. Does anyone have any numbers? I realize that Vizrd
has
references to this, but I'd like to see hard numbers. I have done port
matching for a number of years mostly because I find that there is a lot
of port area that doesn't come close to the gasket opening. I can say
with
"seat of the pants" numbers that my then bone-stock TR6 motor picked up
acceleration when I port matched the head some years back. This was done
at the time because the stock exhaust manifold covered up as much as 10%
of the port space (although the overlap was different on every
cylinder).
So - let's see some numbers so we can lay this one to rest.
rml
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