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Re: ZS 150 to 175 GT6 Conversion

To: triumphs@Autox.Team.Net
Subject: Re: ZS 150 to 175 GT6 Conversion
From: Maurice Dykes <mhdykes@thinkage.on.ca>
Date: Thu, 19 Nov 1998 14:27:53 -0500
Organization: IdentaFone Software
At 09:52 AM 11/19/98 , Scott Swanberg wrote:

>that it has been shown by Triumphtune to work.  The one thing I would
>worry about with Maurice's modified manifold is how much should it be
>enlarged.  Bigger is not always better.  If it is enlarged to much,
you
>risk reducing the mixture velocity, potentially causing separation of
>fuel and air.  The smaller area keeps the velocity high and helps keep
>everything in suspension.  Could be that Maurice hit it right on the
>money, but it seems that with out flow bench testing it's a best guess
>shot.

While what you say is very valid, I must point out however that there
is no point in bolting on a 2" or 1.75" carb to a 1.5" inlet. Just
doesn't make sense.
While Triumptune adapters may appear to work, the credit maybe should
go to the bigger carb and you'll never know how it could have worked
with a ported inlet.
The port should be and usually always is in the same size range as the
butterfly valve (in my manual its called a throttle).

I opened up the inlet so that it had a 2" opening (HD8 SU's) but I
didn't go in too deep and open up anything where the inlet chamber
branches to the runners. If this was a 2 liter engine I would have used
HD6's and made a proper 1.75" opening. I got a lot of information about
this topic over the years from David Vizard's books and had an idea
what would be counter productive.

How thick are these TT spacers? That will also change flow
characteristics as well as pushing the carbs out further to where hood
slope may be a clearance factor.

As far as "hitting it just right" goes, the street became my flowbench.
Measured by a big smile on my face and the surprised look on the face
of a Datsun 2000 owner who has had a friendly rivalry with me over the
years. He is a closet Triumph fan, but likes to bring out old pictures
of Group 44 TR's being led by the Datsuns at Road Atlanta. He now knows
the proof is in the pudding. :-)

If the adapters don't cost much (under a $100) they probably would be
worth a try if you don't have spare manifolds to play with. 

-Maurice
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